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1
Autissier, Laurent. "Développement d'alcoxyamines pour l'ingénierie macromoléculaire." Electronic Thesis or Diss., Aix-Marseille, 2020. http://www.theses.fr/2020AIXM0323.
Abstract:
La dissociation homolytique des alcoxyamines conduit à la formation de deux radicaux, un nitroxyde et un radical alkyle. Cette réaction réversible a été mise à profit pour contrôler les réactions de polymérisation radicalaire de monomères vinyliques ou pour réaliser des additions radicalaires intermoléculaires (IRA). Dans une première partie, notre but a été de développer une alternative plus économique au nitroxyde SG1 pour le contrôle de la polymérisation d’une large gamme de monomères y compris des méthacrylates. Nous avons développé plusieurs structures linéaires aliphatiques et aromatiques mais sans que celles-ci ne présentent les qualités du nitroxyde SG1 pour le contrôle de la polymérisation du styrène et de l’acrylate de n-butyle. Pour le contrôle de la polymérisation des méthacrylates, nous avons étudié des analogues du DPAIO qui se sont montrés aptes à la préparation de copolymères à blocs à base méthacrylate. Dans un second temps nous avons étendu l’IRA à la ligation peptidique et au couplage de polymères. Deux peptides pré-fonctionnalisés par une oléfine et par l’alcoxyamine MAMA-SG1™ ont été couplés par IRA avec de bons rendements. Cette méthode a été nommé Alcoxyamine Peptide Ligation (APL). Le développement de l’alcoxyamine activable 4-VP-SG1 a permis le couplage de type clic par IRA de polymères dans des conditions douces et sans catalyseur ou irradiation lumineuse. La synthèse d’un hydrogel encapsulant in situ une protéine tout en préservant son activité, a validé la compatibilité de cette méthode avec des applications biomédicalesHomolytic dissociation of alkoxyamines yields two radicals, a nitroxide and an alkyl radical. This reversible reaction was used to control radical polymerization of various olefins or to perform intermolecular radical addition (IRA). In a first part, we aimed at developing a cheaper alternative to SG1 radical able to control polymerization of a broad range of monomers including methacrylates. We developed several linear aliphatic and aromatic nitroxide structures. Contrary to SG1 nitroxide, theses structures were not suitable to control radical polymerization of styrene and n-butyl acrylate. As for the control of methacrylates, we studied DPAIO’s analogues, wich were suitable for the preparation of methacrylate based block copolymers. In a second part, we extended the field of IRA to peptide ligation and polymer coupling. Two peptides prefunctionnalized with an olefin and a MAMA-SG1 alkoxyamine were coupled by IRA with good yields. This method was called Alkoxyamine Peptide Ligation (APL). The development of triggered 4-VP-SG1 alkoxyamine allowed performing polymer clicking through IRA in mild conditions without any initiator/catalyst or irradiation source. The synthesis of an hydrogel allowing biological activity retention of in situ encapsulated biomolecule showed that this methodology is relevant for biomedical applications
2
Wang, Aileen Ruiling Zhu Shiping. "Diffusion-controlled atom transfer radical polymerization." *McMaster only, 2005.
3
Belincanta, Juliana. "Homopolimerização e copolimerização via radical livre controlada por radicais nitroxidos." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266269.
Abstract:
Orientador: Liliane Maria Ferrareso LonaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: A polimerização viva/controlada é uma área que vem se desenvolvendo rapidamente no escopo de polímeros e engenharia. A habilidade para preparar copolímeros bem definidos do tipo bloco, estrela, redes poliméricas, bem como outros materiais pelo mecanismo da polimerização via radical livre é talvez a principal razão para o crescente interesse pela academia cientifica e meio industrial neste tipo de polimerização viva/controlada. O interesse industrial se deve a aplicabilidade desta nova técnica em áreas como colas, adesivos, surfactantes, dispersantes, lubrificantes, gel, aditivos, elastômeros termoplásticos, bem como aplicações nas áreas de eletrônica e biomedicina. Vale citar a produção industrial de dispersantes pela polimerização mediada por nitróxidos, um caso de polimerização viva/controlada. Este trabalho tem como objetivo investigar experimentalmente e por modelagem a polimerização em massa via radical livre mediada por TEMPO (2,2,6,6-tetramethyl piperidinyl-1-oxy) de estireno e estireno com divinilbenzeno, sob diversas condições experimentais. Para o caso de homopolimerização foi avaliada uma análise de sensibilidade de como as constantes cinéticas afetam o desempenho do modelo. Reações, não incluídas no modelo original, foram adicionadas ao modelo e testadas. O efeito de diferentes concentrações de TEMPO foi avaliado experimentalmente. Foi observado que esta condição afeta significativamente os resultados. Para o caso de copolimerização, resultados experimentais foram obtidos em diversas temperaturas, e concentração inicial de DVB (divinilbenzeno) e TEMPO. O gel obtido pela polimerização mediada por TEMPO apresenta diferenças marcantes daquele preparado pelo sistema convencional, com relação ao perfil de conversão de monômero. O ponto gel para este caso novo foi obtido em tempos maiores daquele obtido em sistemas convencionais. A versatilidade da polimerização mediada por nitróxidos permite a síntese de um número significativo de novas arquiteturas poliméricas. Espera-se que o modelo proposto, bem como os dados experimentais obtidos neste trabalho, seja útil para um melhor conhecimento desta nova técnica de polimerização. Palavras-chave: polimerização viva/controlada, TEMPO, polimerização em massa, experimental, modelagem
Abstract: Controlled/living radical polymerization (CLRP) is one of the most rapidly developing areas of polymer science and engineering. The ability to prepare well-defined block and graft copolymers, gradient and periodic copolymers, stars, combs, polymer networks, end-functional polymers and many other materials by free-radical mechanisms is perhaps the main reason for the increased academic and industrial interest in CLRP. The industrial interest is triggered by the potential of CLRP in areas as coatings, adhesives, surfactants, dispersants, lubricants, gels, additives, thermoplastic elastomers as well as many electronic and biomedical applications. It is pointed out the industrial production of dispersants by nitroxide-mediated radical polymerization (NMRP), one case of CLRP. This study focus on the model and experimental investigation of TEMPO (2,2,6,6-tetramethyl piperidinyl-1-oxy) mediated free radical polymerization of styrene and styrene-co-divinylbenzene carried out in bulk under different experimental conditions. For homopolymerization case, a sensitivity analyses of how kinetic constants affect the model performance was carried out. Other reactions, not included in the previous model, were included and tested. The effect of different initial concentration of TEMPO was evaluated experimentally. It was shown that this condition affects significantly the results. For copolymerization case, experimental results were obtained for different temperature, and initial concentration of DVB and TEMPO. The gel prepared by NMRP showed remarkable differences from the one prepared in the conventional system, in regard to the monomer conversion profile. The gel point was delayed for the new process compared with conventional systems. The versatility of NMRP permits the synthesis of a number of novel architectures. In conclusion, the model proposed is expected to provide useful guidelines towards a better understanding of the NMRP process. Keywords: controlled/living polymerization, TEMPO, bulk polymerization, experimental, model
Doutorado
Desenvolvimento de Processos Químicos
Doutor em Engenharia Química
4
Mochizuki, Shuto. "Controlled radical polymerization in designed porous materials." Kyoto University, 2019. http://hdl.handle.net/2433/242535.
5
Vieira, Roniérik Pioli 1989. "Modelagem matemática para a otimização e scale up da polimerização radicalar controlada do estireno." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266633.
Abstract:
Orientador: Liliane Maria Ferrareso LonaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: O processo de polimerização radicalar via transferência de átomo (ATRP) consiste numa das técnicas de polimerização radicalar controlada para a síntese de materiais com estruturas macromoleculares específicas. Através desta técnica, podem-se sintetizar homopolímeros monodispersos (baixos índices de polidispersidade), polímeros com funcionalidades terminais ou numa determinada posição da cadeia, o que permite produzir diversos copolímeros (em bloco, gradiente, aleatório etc), possibilitando agregar aos materiais propriedades requisitadas na indústria automobilística e aeroespacial, cosméticos, tintas e adesivos, além de possibilitar a produção de materiais para a liberação controlada de drogas e outras aplicações biomédicas. Apesar de todo este potencial relacionado à ATRP, a maioria das pesquisas encarrega-se de desenvolver novos materiais em escala laboratorial, deixando de lado a condução do processo em escalas comerciais. Neste contexto, o presente trabalho encarrega-se de desenvolver uma modelagem cinética do processo ATRP, juntamente com uma análise dos resultados da simulação para proporcionar aos leitores uma compreensão geral do processo, além de uma ferramenta matemática para futuros trabalhos de otimização e Scale up. A modelagem matemática foi desenvolvida utilizando balanços materiais, para prever perfis de concentração no reator, e o método dos momentos, para prever as massas molares e polidispersidades dos polímeros formados. Os modelos foram resolvidos numericamente em um programa computacional desenvolvido em linguagem Fortran e validados através de dados de literatura utilizando gráficos de dispersão. Por fim, uma análise paramétrica foi realizada com o intuito de estudar o comportamento do processo sob situações práticas, como por exemplo, alterações na constante de equilíbrio do processo (Keq), influência das razões iniciais de catalisador e iniciador sobre as propriedades finais, influência das terminações e transferências de cadeia, além da influência da temperatura de operação do reator
Abstract: Atom transfer radical polymerization (ATRP) is one of controlled radical polymerization techniques for the synthesis of materials with specific macromolecular structures. Using this technique, one can synthesize monodisperse homopolymer (low polydispersity index), end groups polymers or polymers with functionality in a particular position in the chain, which allows to produce different copolymers (block, gradient, random, etc.), allowing aggregate materials properties required in automotive and aerospace industry, cosmetics, paints and adhesives, and enable the production of materials for the controlled delivery of drugs and other biomedical applications. Despite this potential related to ATRP, most research is responsible for developing new materials on the laboratory scale, leaving aside the conduct of proceedings at commercial scales. In this context, this paper undertakes to develop a kinetic modeling of the ATRP process, together with an analysis of the simulation results to give readers a general understanding of the process, as well as a mathematical tool for future work on optimization and Scale up. A mathematical model was developed using material balances to predict concentration profiles in the reactor, and the method of moments to predict the molecular weight and polydispersities of the polymers formed. The models were solved numerically on a computer program developed in Fortran and validated through literature data using scatter plots. Finally, the parametric analysis was performed in order to study the behavior of chemical species in practical situations, such as changes in the process equilibrium constant (Keq), the influence of the initial ratio of catalyst and initiator on the final properties, influence terminations and chain transfers, beyond the influence of the operating temperature of the reactor
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química
6
Yin, Meizhen. "Synthesis and controlled radical polymerization of multifunctional monomers." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2004. http://nbn-resolving.de/urn:nbn:de:swb:14-1091453146703-47835.
Abstract:
Multifunctional monomers on the basis of acryl- and methacryl derivatives were synthesized and different protective groups were used. After polymerization the protective groups were removed by different methods. Various initiators for the NMP of the monomers were synthesized and the reaction conditions were optimized. The results showed that NMP was not a suitable method for multifunctional acryl- and methacryl derivatives to achieve well-defined homopolymers, although it was successful for control of polymerization of styrene and block copolymerization of multifunctional acryl- and methacryl derivatives with alkoxyamine terminated polystyrene. The ATRP of multifunctional acrylates and methacrylates has been successfully performed, as well as the block copolymerization of multifunctional acrylates and methacrylates. Relatively low polydispersities of the corresponding polymers (PD=1.18-1.36) and reasonably high rates of polymerization could be achieved when Me6TREN and PMDETA were used as ligands. However, the ATRP of multifunctional acrylamides and methacrylamides failed. The RAFT-polymerization of styrene, acrylamide and acrylate using BDTB as a CTA and AIBN as an initiator afforded polymers with narrow molecular weight distribution (PD=1.13-1.26). A kinetic investigation and the further synthesis of block copolymers using dithioester-terminated homopolymers as macroCTAs showed that the RAFT polymerization of acrylamide M9b proceeded in a living manner. However, BDTB does not control the reaction of methacrylic monomers, such as methacrylates and methacrylamides. The bulk phase behavior of the block copolymers were examined by means of DSC and the surface behaviors of block copolymers as thin layers were examined with AFM. Two-phase transitions in the block copolymers were observed clearly by DSC, indicative of the appearance of phase separations, which were seen in an AFM image. In conclusion, multifunctional acryl- and methacryl derivatives failed to achieve well-defined homopolymers by NMP. However, this method was successful for block copolymerization of multifunctional acryl- and methacryl derivatives with alkoxyamine terminated polystyrene. Multifunctional acrylates and methacrylates were successfully homopolymerized and block copolymerized by ATRP. Multifunctional acrylates and acrylamides were suitable for homopolymerization and block copolymerization by the RAFT process. Thus far, it is difficult to homopolymerize multifunctional methacrylamides in controlled way.
7
Heredia, Karina Lynn. "Synthesis of polymer bioconjugates using controlled radical polymerization." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1583873071&sid=37&Fmt=2&clientId=1564&RQT=309&VName=PQD.
8
Qi, Genggeng. "Unconventional radical miniemulsion polymerization." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26547.
Abstract:
Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Jones, Christopher W.; Committee Chair: Schork, F. Joseph; Committee Member: Koros, William J.; Committee Member: Lyon, Andrew; Committee Member: Nenes, Athanasios. Part of the SMARTech Electronic Thesis and Dissertation Collection.
9
Gonçalves, Maria Cecilia. "Estudo experimental da polimerização via radical livre controlada em presença de radicais nitroxido (NMRP)." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266346.
Abstract:
Orientador: Liliane Maria Ferrareso LonaDissertação (mestrado) - Universidade Estadual de Campinas. Faculdade de Engenharia Quimica
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Resumo: A polimerização via radical livre controlada mediante radicais nitróxido (NMRP) tem recebido cada vez mais atenção como uma técnica para produção de polímeros com estrutura altamente controlada. Distribuições de pesos moleculares estreitas são obtidas, com polidispersidades baixas. Neste trabalho, será estudado o processo NMRP, no qual ocorre a adição de um radical nitróxido estável, como o 2,2,6,6-tetrametil-l-piperidinoxil (TEMPO) para capturar o radical em crescimento. Embora o processo NMRP de ao polímero características controladas (polidipersidades baixas e pesos moleculares que aumentam linearmente com a conversão), ainda existe um desafio nos processos controlados, por apresentarem baixas velocidades de reação. O objetivo principal deste trabalho está focado num estudo experimental do processo NMRP visando aumentar a velocidade de reação sem perder as características principais do processo. O efeito de dois iniciadores BPO (peróxido de benzoíla) e TBEC (tert-butilperóxido-2-etilhexil carbonato) foi analisado. Observou-se que o TBEC (iniciador com constante de decomposição baixa) foi capaz de aumentar significativamente a taxa de polimerização do processo NMRP, quando comparado ao BPO, pois conversões mais altas foram obtidas, num mesmo tempo de reação, mantendo a característica controlada do sistema. O uso do TBEC apresenta uma vantagem frente ao BPO em processos controlados, não somente porque reduz o tempo de reação, mas também porque concentrações menores de iniciador e controlador foram usadas, obtendo uma taxa de reação ainda maior, o que reduz o custo operacional. Para as condições estudadas, comprovou-se experimentalmente que a taxa de reação é inversamente proporcional à concentração inicial de TEMPO, para uma mesma concentração de iniciador. A análise dos resultados através da aplicação da técnica de planejamento de experimento auxiliou numa melhor compreensão do sistema e na obtenção de condições ótimas de operação para se obter baixas polidispersidades e baixos tempos de polimerização
Abstract: NMRP process (Nitroxide Mediated Radical Polymerization) has received increasing attention as a technique for production polymers with highly controlled structures, narrow molecular weight distribution (MWD) and polydispersity index dose to 1.0. In this work 2,2,6,6-tetramethyl-l-piperidinoxyl (TEMPO) is used as the stable radical to reversibly terminate the growing polymer chain. Polymerizations were performed in ampoules, using TBEC (tert-butylperoxy-2-ethylhexyl carbonate) and BPO (benzoyl peroxide) as initiators. With the purpose of enhancing the reaction rate for NMRP process maintaining the controlled and living characteristics of the polymer synthesized (low polidispersity and molecular weights increasing linearly with conversion) an experimental study was done to evaluate the effect of two different initiators (BPO and TBEC). It was observed that TBEC (initiator with low decomposition rate) was able to enhance significant1y the polymerization rate compared to BPO, keeping the living and controlled characteristics of the system. The results show that TBEC seems to be a promising initiator that make the NMRP process more efficient, not only because it reduces the polymerization time, but also because it allows smaller amounts of controller and initiator to be used. For the operational conditions studied, experimental results with TBEC exposed that the polymerization rate in inversely proportional to the initial concentration of TEMPO, for the same amount of initiator. Using a statistical planning, it was possible to obtain a better understanding of the system and to search for operating conditions that bring low polydispersity and low reaction rates. Finally, the results are expected to have significant benefits for controlled polymerization on an industrial setting
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química
10
Minaux, Eric. "Controlled radical polymerization at pressures up to 2000 bar." Doctoral thesis, [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=962677035.
11
Özyürek, Zeynep. "Thermoresponsive Glycopolymers via Controlled Radical Polymerization (RAFT) for Biomolecular Recognition." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1190291104620-73670.
Abstract:
Stimuli responsive polymers (SRP) have attracted a lot of attention, due to their potential and promising applications in many fields, as protein-ligand recognition, on-off switches for modulated drug delivery or artificial organs. Poly(N-isopropylacrylamide) (PNIPAM) is one of the most widely studied polymers due to its lower critical solution temperature (LCST) at ~ 32° C in aqueous solution. Additionally, glycopolymers, where free sugar units are present, have potentially interesting applications especially in bio-recognition where sugars play an important role. In this work, our interest was focused on the synthesis of glycomonomers and its block- and random- copolymers with NIPAM. NIPAM homopolymers with an active chain transfer unit at the chain end could be prepared by RAFT. They were used as macro-chain transfer agents to prepare a variety of sugar containing responsive block copolymers from new glycomonomers by the monomer addition concept. The LCSTs of the aqueous solutions of the copolymers are affected strongly by the comonomer content, spacer chain length of the glycomonomer and the chain architecture of the copolymers. These polymers were coated on a solid substrate by spin coating and crosslinked by plasma immobilization. Characterization of the polymers was performed by nuclear magnetic resonance spectroscopy (NMR), ultraviolet (UV), dynamic light scattering (DLS, detection of aggregation behaviour) and gel permeation chromatography (GPC). Polymer films were investigated by ellipsometry, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) regarding their surface properties. Afterwards sulfation of sugar – OH groups was performed in order to obtain heparin like structure, as heparin exhibits numerous important biological activities, like good interaction with diverse proteins. Finally, affinity of the polymers (sulfated and non sulfated form) on a solid support to the endothelial cells was investigated.
12
Yu, Bonan. "Optimization of Benzocyclobutene Containing Methacryalte Structure for Controlled Radical Polymerization." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1398938075.
13
Simms, Ryan W. "Living/controlled Polymerization Conducted in Aqueous Based Systems." Thesis, Kingston, Ont. : [s.n.], 2007. http://hdl.handle.net/1974/700.
14
Bortolamei, Nicola. "Electrochemistry for atom transfer radical polymerization: from mechanism to more controlled synthesis." Doctoral thesis, Università degli studi di Padova, 2012. http://hdl.handle.net/11577/3422094.
Abstract:
Living/controlled radical polymerizations (L/CRPs) have been developed in the second half of the nineties and nowadays are among the most powerful and effective polymerization techniques for the preparation of advanced polymeric materials with well defined properties and high value.
Atom Transfer Radical Polymerization (ATRP) has recorded the highest success in the field of L/CRP, thanks to its versatility and easiness of application. The first goal of this Ph.D. thesis is to understand and develop Cu-catalyzed ATRP through an electrochemical approach, with particular regard to the properties of the catalysts, initiators and propagating radicals, and the rationalization of the activation mechanism. Besides these fundamental aspects, a second important goal is to open a new way to enhance the control of the polymeric synthesis and allow the catalyst regeneration by means of electrochemical tools.Le polimerizzazioni radicaliche controllate (Controlled radical polymerization, CRP) sono state sviluppate a partire dalla metà degli anni '90, e attualmente sono tra le più potenti ed efficaci metodologie di polimerizzazione per ottenere materiali polimerici avanzati con proprietà ben definite ed alto valore aggiunto. La polimerizzazione radicalica a trasferimento di atomo (Atom Transfer Radical Polymerization, ATRP) è la tecnica che ha riscontrato il maggior successo nel campo delle CRP grazie alla sua versatilità e facilità di applicazione. Scopo di questa tesi di dottorato è di fornire un contributo alla comprensione e allo sviluppo di ATRP catalizzata da rame attraverso un approccio elettrochimico, con particolare riguardo alle proprietà di: catalizzatore, specie dormiente e radicali propaganti, e alla comprensione del meccanismo di attivazione. Inoltre, un secondo importante obbiettivo è quello di sviluppare nuove metodologie elettrochimiche atte ad aumentare il controllo delle sintesi polimeriche e permettere la rigenerazione del catalizzatore.
15
Aran, Bengi. "Polymerization And Characterization Of Methylmethacrylate By Atom Transfer Radical Polymerization." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605042/index.pdf.
Abstract:
In this work, methylmethacrylate, MMA was polymerized by ATRP method to obtain low molecular weight living polymers. The initiator was p-toluenesulfonylchloride and catalyst ligand complex system were CuCl-4,4&rsquodimethyl 2,2&rsquo
bipyridine. Polymers with controlled molecular weight were obtained. The polymer chains were shown by NMR investigation to be mostly syndiotactic. The molecular weight and molecular weight distribution of some polymer samples were measured by GPC method. The K and a constants in [h]=K Ma equation were measured as 9.13x10-5 and 0.74, respectively. FT-IR and X-Ray results showed regularity in polymer chains. The molecular weight-Tg relations were verified from results of molecular weight-DSC results.
16
Aksakal, Resat. "Functional polymers via Cu-mediated radical polymerization." Thesis, Queen Mary, University of London, 2018. http://qmro.qmul.ac.uk/xmlui/handle/123456789/36215.
Abstract:
This work reports the investigation of Cu-mediated polymerization systems and its limits, in order to obtain functional branched polymers, in particular star-shaped and graft-shaped polymers. A novel initiator structure has allowed developing a new approach to synthesise sequence controlled multiblock star polymers via Cu-mediated reversible deactivation radical polymerization (RDRP) in water. This technique allows the preparation of pentablock star shaped polymers in just under 90 minutes of reaction time. The obtained polymers had a good agreement between theoretical and experimental molecular weights and excellent control over molecular weight distribution. Alternatively, the Cu-mediated RDRP of star polymers using a British 1 penny coin was described, displaying similar results as in the literature, providing better experimental conditions. As the copper coin was recovered unharmed, the catalyst was found to be economically very effective. Furthermore, poly(2-ethyl oxazoline) (PEtOx) was polymerized with good control and partially hydrolysed to poly(ethylene imine) (PEI) to yield PEtOx-r-PEI using a microwave reactor. The secondary amines of PEI was converted to macroinitiators, to allow the polymerization of acrylamides in aqueous medium, resulting in graft type polymers based on a poly(oxazoline) backbone with acrylamide side chains. Finally, the synthesis of carbohydrate-monomers was described, which allows to obtain monomers with a different number of carbohydrates (one, two or three). These monomers were polymerised via aqueous SET-LRP, to explore their interaction with carbohydrate binding lectins and to understand the impact on binding of carbohydrate density on polymers and polymer chain length.
17
Russum, James. "Controlled Radical Polymerizations in Miniemulsions: Advances in the Use of RAFT." Diss., Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-10112005-105314/.
Abstract:
Thesis (Ph. D.)--Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2006.Jones, Christopher, Committee Chair ; Schork, F. Joseph, Committee Co-Chair ; Weck, Marcus, Committee Member ; Meredith, Carson, Committee Member ; Agrawal, Pradeep, Committee Member.
18
Carlmark, Anna. "Complex Macromolecular Architectures by Atom Transfer Radical Polymerization." Doctoral thesis, KTH, Fibre and Polymer Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3740.
Abstract:
Controlled radical polymerization has proven to be a viableroute to obtain polymers with narrow polydispersities (PDI's)and controlled molecular weights under simple reactionconditions. It also offers control over the chain-]ends of thesynthesized polymer. Atom transfer radical polymerization(ATRP) is the most studied and utilized of these techniques. Inthis study ATRP has been utilized as a tool to obtain differentcomplex macromolecular structures.
In order to elaborate a system for which a multitude ofchains can polymerize in a controlled manner and in closeproximity to one another, a multifunctional initiator based onpoly(3-ethyl-3-(hydroxymethyl)oxetane was synthesized. Themacroinitiator was used to initiate ATRP of methyl acrylate(MA). The resulting dendritic-]linear copolymer hybrids hadcontrolled molecular weights and low PDI's. Essentially thesame system was used for the grafting of MA from a solidsubstrate, cellulose. A filter paper was used as cellulosesubstrate and the hydroxyl groups on the cellulose weremodified into bromo-]ester groups, known to initiate ATRP.Subsequent grafting of MA by ATRP on the cellulose made thesurface hydrophobic. The amount of polymer that was attached tothe cellulose could be tailored. In order to control that thesurface polymerization was -eliving-f and hence that thechain-]end functionality was intact, a second layer of ahydrophilic monomer, 2-hydroxyethyl methacrylate, was graftedonto the PMA- grafted cellulose. This dramatically changed thehydrophilicity of the cellulose.
Dendronized polymers of generation one, two and three weresynthesized by ATRP of acrylic macromonomers based on2,2-bis(hydroxymethyl)propionic acid. In the macromonomerroute, macromonomers of each generation were polymerized byATRP. The polymerizations resulted in polymers with low PDI's.The kinetics of the reactions were investigated, and thepolymerizations followed first-order kinetics when ethyl2-bromopropionate was used as the initiator. In the-egraft-]onto-f route dendrons were divergently attached to adendronized polymer of generation one, that had been obtainedby ATRP.
19
Ejaz, Muhammad. "Controlled Surface Grafting of Well-Defined Polymers by Living Radical Polymerization Techniques." 京都大学 (Kyoto University), 2001. http://hdl.handle.net/2433/150698.
20
De, Camargo Chaparro Thaissa. "Synthesis of nanocomposites with anisotropic properties by controlled radical emulsion polymerization Lorena." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1045/document.
Abstract:
L'objectif de ce travail de thèse est de préparer des latex nanocomposites à base d’argile, la Laponite RD, en émulsion aqueuse, à l'aide de la polymérisation radicalaire contrôlée par transfert de chaîne réversible par addition-fragmentation (RAFT). Les plaquettes de Laponite ont été choisies comme charge inorganique surtout pour leur anisotropie de forme, ce qui pourrait permettre l’elaboration de films nanostructurés, mais aussi pour leurs propriétés thermiques et mécaniques, leur pureté chimique élevée et la distribution uniforme en taille des plaquettes. Des polymères hydrophiles (macroRAFT) à base de polyéthylène glycol (PEG), d’acide acrylique (AA) ou de méthacrylate de N,N- diméthylaminoéthyle (DMAEMA) et comportant des unités hydrophobes d’acrylate de n-butyle (ABu) (dans certains cas) et un groupe trithiocarbonate terminal, ont été tout d'abord synthétisés. Ensuite, l'interaction entre les macroRAFTs et l’argile a été étudiée à travers le tracé des isothermes d'adsorption. En agissant comme des agents de couplage et des stabilisants, ces macroRAFTs ont eté utilisés dans la copolymérisation en émulsion du (méth)acrylate de méthyle et de l’ABu en mode semi-continu en presence d’argile. Des particules de latex hybrides de différentes morphologies ont été obtenues et les morphologies ont été reliées à la nature et à la concentration de l’agent macroRAFT, au pH de la dispersion macroRAFT/Laponite, à la température de transition vitreuse du copolymère final (fonction de la composition du mélange de monomères hydrophobes) et aux conditions de polymérisation. Les analyses par cryo-MET indiquent des plaquettes de Laponite décorées par des particules de polymère (plusieurs particules de latex en surface des plaquettes d'argile), des particules ‘haltère’, janus, ‘carapace’ (particules de latex décorées en surface par les plaquettes de Laponite) ou encore des particules multi-encapsulées (plusieurs plaquettes encapsulées dans chaque particule de latex). Les propriétés mécaniques des films de polymère/Laponite ont été étudiées par spectrométrie mécanique dynamique et corrélées à la morphologie des particules et à la microstructure des filmsThe aim of this work is to prepare Laponite RD-based nanocomposite latexes by aqueous emulsion polymerization, using the reversible addition-fragmentation chain transfer (RAFT) polymerization. Laponite platelets were selected as the inorganic filler due, especially, to their anisotropic shape, which allows the production of nanostructured films, but also for their thermal and mechanical properties, their high chemical purity and the uniform dispersity of the platelets. Hydrophilic polymers (macroRAFT) composed of poly(ethylene glycol) (PEG), acrylic acid (AA) or N,N-dimethylaminoethyl methacrylate (DMAEMA) and comprising hydrophobic n-butyl acrylate (BA) units (in some cases) and trithiocarbonate terminal group were initially synthesized. Then, the interaction between the macroRAFTs and the clay was studied through the plot of adsorption isotherms. By acting as coupling agents and stabilizers, the macroRAFT agents were used in the emulsion copolymerization of methyl (meth)acrylate and BA by semi-continuous process in the presence of the clay. Hybrid latex particles with different morphologies were obtained and the results were associated to the nature and concentration of the RAFT (co)polymers, to the pH of the macroRAFT/Laponite dispersion, the glass transition temperature of the final copolymer (function of the composition of the hydrophobic monomers mixture) and to the polymerization conditions. The cryo-TEM images indicate the formation of polymerdecorated Laponite platelets (several latex particles located at the surface of the platelets), dumbbell-like, janus, Laponite-decorated (armored) latex particles, and multiple encapsulated particles (several platelets inside each latex particle). The mechanical properties of polymer/Laponite films were studied by dynamic mechanical analysis and correlated with the particles morphology and the films microstructure
Este trabalho de tese tem como objetivo a preparação de látices nanocompósitos à base da argila Laponita RD em emulsão aquosa, via polimerização radicalar controlada por transferência de cadeia via adição-fragmentação reversível (RAFT). A Laponita foi escolhida como carga inorgânica devido principalmente à forma anisotrópica de suas lamelas, o que permite a elaboração de filmes nanoestruturados, mas também por suas propriedades térmicas e mecânicas, por sua alta pureza química e pela distribuição uniforme, em termos de tamanho, de suas partículas. Inicialmente, polímeros hidrofílicos (macroRAFT) à base de poli(etileno glicol) (PEG), de ácido acrílico (AA) ou de metacrilato de N,N-dimetilaminoetila (DMAEMA) que contêm unidades hidrofóbicas de acrilato de nbutila (ABu) (em alguns casos) e um grupo tritiocarbonílico terminal foram sintetizados. Em seguida, a interação entre os macroagentes de controle (macroRAFTs) e a argila foi estudada através de isotermas de adsorção. Atuando como agentes de acoplamento e estabilizantes, esses macroRAFTs foram então utilizados na copolimerização em emulsão do (met)acrilato de metila e do ABu em processo semicontínuo na presença da argila Laponita. Partículas de látex híbrido de diferentes morfologias foram obtidas e os resultados foram correlacionados à natureza e à concentração dos macroRAFTs, ao pH da dispersão macroRAFT/Laponita, à temperatura de transição vítrea do copolímero final (função da composição da mistura de monômeros hidrofóbicos) e às condições de polimerização. As análises de cryo-TEM indicam a formação de lamelas de Laponita decoradas com partículas de polímero (várias partículas de látex localizadas na superfície das lamelas), de partículas do tipo dumbbell, janus, blindadas (partículas de látex decoradas com lamelas de argila em sua superfície) ou ainda de partículas multiencapsuladas (diversas lamelas encapsuladas dentro de uma única partícula de látex). As propriedades mecânicas dos filmes de polímero/Laponita foram estudadas por análise dinâmico-mecânica e correlacionadas à morfologia das partículas e à microestrutura dos filmes
21
Higashimura, Hideyuki. "Radical-controlled oxidative polymerization of phenols : a new methodology for polymer synthesis." 京都大学 (Kyoto University), 2005. http://hdl.handle.net/2433/144858.
22
Çakir, Pinar. "Molecularly imprinted polymer nanostructures by controlled / living radical polymerization with multi-iniferters." Compiègne, 2012. http://www.theses.fr/2012COMP2018.
Abstract:
Les polymères à empreintes moléculaires (MIPs) sont des matériaux synthétiques contenant des cavités capables de reconnaître spécifiquement une molécule cible. Ils se présentent comme une alternative intéressante face aux anticorps biologiques en raison de leur meilleure stabilité chimique et physique, leur meilleure disponibilité et leur moindre coût. Traditionnellement, les MIPs sont synthétisés par polymérisation de monolithes, qui sont ensuite broyés mécaniquement, engendrant des particules de taille micrométrique et de formes irrégulières. Durant ces dernières années, de nombreuses techniques de polymérisation ont été développées afin d’obtenir des particules MIP sphériques de tailles micro et nanométriques, et plus particulièrement des nanogels quasi-solubles. Dans l’optique d’une application en biologie, des tailles de quelques nanomètres - de l’ordre de grandeur de la taille des protéines – sont souhaitées, ce qui pose un réel défi pour leur synthèse, car la faible densité du matériau (une particule ne consiste que de quelques chaines de polymère) s'oppose à l'impression d'une mémoire moléculaire. Nous avons développé une nouvelle approche de synthèse de MIP nanogels dont la taille est proche de celle des anticorps naturels. Notre stratégie est basée sur l’utilisation d’un nouveau type d'amorceur pour la polymérisation radicalaire contrôlée comprenant des fonctions iniferter multiples attachées à un noyau dendritique. Cela permet de générer une concentration localement élevée de radicaux et ainsi, d'obtenir des nanogels de polymère dont la densité est augmentée. Ces travaux de thèse ont conduit à l’obtention des nanogels de MIP de 17 nm de diamètre avec un effet impression appréciable, une bonne affinité pour la cible, le beta-antagoniste propranolol, et une sélectivité moléculaire prononcée. En plus de la synthèse des nanogels solubles de MIP, des motifs de MIP micro et nanostructurés ont été greffés sur des surfaces planes de silicium. Le multiiniferter a été imprimé à la surface par lithographie douce, et fixé chimiquement par son groupement carboxyle central. Les MIPs ont ensuite été synthétisés par une approche « bottom up », caractérisés par spectroscopie d'émission optique, la spectroscopie Raman et la microscopie à force atomique, et la reconnaissance moléculaire de la cible a été visualisée par microscopie de fluorescence. Ces nouveaux matériaux, nanogels et surfaces imprimées offrent de nombreuses perspectives pour la détection par biocapteurs et biopuces, en particulier dans le domaine du biomédicalMolecularly imprinted polymers (MIPs) are synthetic materials with specific recognition properties for target molecules. They are considered an alternative to antibodies and are characterized by a higher chemical and physical stability, better availability and lower cost. Historically, MIPs were synthesized as bulk monoliths that were subsequently broken down mechanically in order to form particles of a size in the micrometer range, with irregular shapes. During the last decade, research has focused on the direct synthesis of spherical MIP micro and nanoparticles, and, more recently, on protein-sized, quasi-soluble MIP nanogels in order to widen the application range of MIPs in the biological field. The main difficulty of synthesizing MIPs with diameters in the low nm region is the low density of the resulting polymer network consisting only of a few polymer chains, which makes it difficult to imprint and maintain a molecular memory. In this thesis, we propose an original approach to the synthesis of quasisoluble MIP nanogels with a size in the low nm range, close to that of real antibodies. The proposed procedure involves a new type of initiator for controlled/living radical polymerization, based on multiple iniferter moieties attached to a dendritic core. This allows for the generation of a higher local radical density, and thus for the synthesis of denser nanogels. By using this strategy, MIP Nanogels of 17 nm size with an appreciable molecular imprinting effect, a good affinity for the target molecule, the chiral drug propranolol, and a good selectivity were obtained. In addition, these multiiniferters were also used for the bottom-up synthesis of thin MIP patterns on silicon wafers, by surface-initiated polymerization. The multi-iniferter was printed on to the surface by soft lithography and chemically attached through its carboxyl-functionalized core, followed by the in-situ synthesis of the MIP. Well defined MIP patterns were obtained, which were characterized by optical emission spectroscopy, Raman spectroscopy, atomic force microscopy, and the specific binding of the target molecule was visualized by fluorescence microscopy. We believe that the synthesis, in solution and at surfaces, of protein-size MIP nanogels with specific recognition properties will provide new opportunities for biosensors and biochips technologies in biomedical applications
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Amato, Douglas Vincent. "LATENT CYSTEINE RESIDUES FROM POLYMERS PREPARED VIA FREE AND CONTROLLED RADICAL POLYMERIZATIONS." DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/972.
Abstract:
One less commonly used “click” reaction is thiazolidine chemistry. Thiazolidine chemistry is a commonly used reaction used in biological systems because the reaction requires the presence of both cysteine (a common amino acid) and an aldehyde or ketone. If cysteine residues could be incorporated into a polymer then a variety of applications could be developed. Polymers containing free thiols (aka thiomers) have developed in the last decade to become great mucoadhesives. If there was a facile route to control the amount of free thiols along the polymer then more fine-tuned and potentially stronger adhesives could be made. For these reasons the attachment of cysteine residues in a facile way via reversible addition fragmentation chain transfer (RAFT) polymerization or small molecule synthesis was researched. The incorporation of latent cysteine residues into the polymer via post polymerization modification proved to be less successful. However protected cysteine molecules have been successfully ligated onto polymerizable monomers and have been show to be easily deprotected in the presence of an acid source.
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Vosloo, Johannes Jacobus. "Controlled free radical polymerization in miniemulsion using Reversible Addition-Fragmentation Chain Transfer (RAFT)." Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/52174.
Abstract:
Thesis (MSc)--Stellenbosch University, 2001.ENGLISH ABSTRACT: A novel approach to conducting controlled free radical polymerization in aqueous systems using Reversible Addition-Fragmentation Chain Transfer (RAFT) has been studied. When conducting RAFT in aqueous systems, reaction conditions must be chosen such that monomer transport across the aqueous-phase is either eliminated or facilitated. This is to prevent the formation of the red layer associated with RAFT in emulsions. The formation of the red layer is ascribed to the inability of waterinsoluble, dithiobenzoate-endcapped oligomers to be sufficiently transported across the aqueous phase. The novel approach in this study focussed on eliminating monomer transport and comprises two fundamental steps: the synthesis of dithiobenzoate-encapped oligomers in bulk followed by miniemulsification of these oligomers to yield a polymerizable miniemulsion. Dithioesters that act as chain transfer agents in the RAFT -process were synthesized in situ, thereby eliminating laborious and time-consuming organic purification procedures of dithioesters. In situ formation of the RAFT-agents involved conducting the reaction between di(thiobenzoyl) disulfide and conventional azo-initiators of differing structures in the presence of monomer. The structure of the chosen azo-initiator played a role in the efficiency of the RAFT process when the reaction was conducted in the presence of monomer to control the free radical polymerization process. Synthesis of the oligomers was performed by heating di(thiobenzoyl) disulfide and a selected azo-initiator, in the presence of monomer for a specific reaction duration in bulk. After the reaction was stopped, these oligomers were then miniemulsified by adding water, surfactant and cosurfactant, followed by the application of shear to form the resulting mini emulsion. The free radical polymerization of the dithiobenzoate-endcapped oligomers in the miniemulsion proceeded in a controlled manner with molecular weight increasing in a linear fashion with increasing conversion, while polydispersities remained low. The familiar red layer formation associated with RAFT polymerization in conventional emulsions was not observed under these conditions. The effects of changing the cosurfactant (hydrophobe) as well as changing the degree of polymerization of the emulsified oligomers were also investigated and described.
AFRIKAANSE OPSOMMING: Hierdie studie is geloods om 'n nuwe benadering tot die beheerde vry-radikaal polimerisasie in water gebaseerde sisteme te ondersoek. Daar is spesifiek gekyk na die uitvoer van die RAFT (Reversible Addition-Fragmentation Chain Transfer) proses in emulsies. Wanneer RAFT in emulsies toegepas word, moet die toestande waaronder die reaksie uitgevoer word, versigtig opgestel word. Die toestande moet so gekies word dat die vervoer van monomere deur die waterfase óf geëlimineer word óf gefasiliteer word. Dit word gedoen om die faseskeiding in die vorm van 'n rooi laag, wat so kenmerkend van RAFT -polimerisasie in emulsies is, te voorkom. Hierdie faseskeiding vind plaas omdat die vervoer van ditiobensoaat endgroep-bevattende oligomere deur die waterfase tydens interval II, moeilik is a.g.v. hulle oplosbaarheid in water. Die nuwe benadering wat hier bestudeer is, het twee basiese stappe. Eerstens word die ditiobensoaat endgroep-bevattende oligomere in bulk gesintetiseer. Dit word gevolg deur die emulsifisering van die oligomere. Hierna vind verdere polimerisasie van die oligomere plaas deur die dormante oligomere te heraktiveer. Die ditio-esters wat as kettingoordrag agente optree in die RAFT proses, word in situ gesintetiseer. Hierdie modifikasie sny tydrowende organiese suiweringsmetodes uit. Die in situ RAFT agente word gesintetiseer deur di(tiobensoïel) disulfied met verskillende konvensionele azo-inisieerders te laat reageer. Die struktuur van die spesifieke azoinisieerder het wel 'n rol gespeel in die effektiwiteit van die RAFT proses om molekulêre massa te beheer as bg. reaksie in die teenwoordigheid van monomere uitgevoer is. Die sintese van die oligomere is gedoen deur di(tiobensoïel) en 'n azo-inisieerder te verhit in die teenwoordigheid van monomere. Die reaksie is gedoen in bulk en die graad van polimerisasie van die oligomere is beheer deur die reaksie te stop by verskillende tydstippe. Nadat die bulk reaksie gestop is, is hierdie oligomere ge-emulsifiseer deur die oligomere te meng met 'n seep, hidrofoob en water. Hierdie mengsel word dan onderwerp aan 'n vermengingskrag om 'n polimeriseerbare mini-emulsie te vorm. Die voortsetting van die polimerisasie van die oligomere in die mini-emulsie het op 'n beheerde wyse verloop, m.a.w. molekulêre massa wat linieêr toeneem met stygende omsetting. Polidispersiteit indekse van die polimere het deurentyd laag gebly in die stabielste sisteme. Onder hierdie toestande was daar geen kenmerkende rooi laagvorming te bespeur nie. Die effekte wat die verandering van die hidrofoob, asook die verandering van die graad van polimerisasie van die oligomere op die sisteem gehad het, is onder andere ook ondersoek en beskryf.
25
Gonzato, Carlo. "Chemical nanosensors based on molecularly imprinted polymer nanocomposites synthesized by controlled radical polymerization." Compiègne, 2012. http://www.theses.fr/2012COMP2035.
Abstract:
Les polymères à empreintes moléculaires (MIP, pour molecularly imprinted polymers en anglais) sont des récepteurs synthétiques, parfois appelés "anticorps en plastique", capables de reconnaitre et fixer spécifiquement une molécule cible. L’impression moléculaire s’est imposée, durant les trente dernières années, comme une technique pour la synthèse des structures réticulées possédant une remarquable affinité et sélectivité vis-à-vis d’une espèce chimique utilisée comme molécule empreinte dans un procédé de moulage au niveau moléculaire. La grande variété de matériaux et de formats accessibles à cette technique lui ont permis de trouver un grand nombre d’applications, telles que la séparation, les capteurs, la catalyse, le ré-largage contrôlé de médicaments. Depuis leur apparition, la plupart des MIPs a été synthétisée par polymérisation radicalaire libre (FRP) des monomères vinyliques. Cette méthode de polymérisation représente un excellent choix en termes de simplicité de mise en place, tolérance par rapport aux solvants et aux différents groupements fonctionnels des ingrédients. Cependant, plusieurs désavantages liés à cette technique limitent la possibilité d’obtenir un contrôle adéquate vis-à-vis de certaines caractéristiques fondamentales pour des applications en nano-technologies. L’introduction des techniques de polymérisation radicalaire contrôlée/vivante (CRP) a donc représentée une avancée importante et a permis de dépasser certains limites associés aux MIPs synthétisés par FRP. Dans ce contexte, ce travail de thèse a étudié les avantages provenant de l’utilisation d'une méthode CRP, le RAFT, pour la synthèse des MIP. Ce travail a été mené en se focalisant sur les caractéristiques principales des CRPs : le caractère vivant et, en même temps, contrôlé. Dans un premier temps, nous avons utilisé l’aspect vivant de la polymérisation pour la synthèse des nanocomposites MIP, possédant des propriétés superparamagnétiques. Celle-ci a été effectuée par polymérisation de couches p(EGDMA-co-MAA) par RAFT amorcée à la surface des particules de Fe3O4 préfonctionnalisées avec des groupements amine. Le greffage de ces couches a été obtenu en employant des ultrasons comme source d'agitation, et en testant différents solvants pour en apprécier l’influence sur la structure et la morphologie des composites résultants. Nous avons démontré que le greffage se produit d’une façon homogène, et que grâce au caractère vivant de la polymérisation RAFT, les composites peuvent être fonctionnalisés davantage, par exemple par des chaines p(EGMP), pour ajuster leur propriétés de surface. Dans un deuxième temps, nous nous sommes consacrés à une étude comparative visant la mise en évidence des avantages de la RAFT par rapport à la FRP en termes de performances des MIP acryliques et méthacryliques. Pour mieux apprécier les différences induites par la méthode de polymérisation, le dégrée de réticulation et donc la flexibilité des réseaux ont été variés de façon systématique. Cette stratégie a permis de bien apprécier les différences induites par chaque technique de polymérisation. Les résultats ont démontré que la RAFT permet de synthétiser des MIPs ayant une meilleure affinité pour leur molécule cible, et que cette amélioration est due à une distribution plus homogène des points de réticulation au sein du réseau. Finalement, nous avons appliqué la RAFT pour la synthèse de nanocapteurs individuels basés sur des composite MIP intégrant des nanoparticules d'or, et utilisant la spectroscopie Raman exaltée (SERS) pour la détectionMolecularly imprinted polymers (MIPs) are synthetic receptors, also known as antibody mimics, that can specifically bind target molecules. Molecular imprinting has emerged, over the last 30 years; it is an extremely versatile strategy for synthesizing networks possessing high affinity and selectivity for a chemical species, used as a molecular template during their synthesis. The wide variety of materials and formats that are accessible through this strategy has resulted in a broad spectrum of applications for such MIPs, ranging from separation to sensing, catalysis, drug delivery, etc. Since the beginning, the great majority of the imprinted networks has been synthesized by assembling vinyl monomers via free-radical polymerization (FRP). This polymerization method represents a convenient choice for synthesizing MIPs, due to its easy setup, versatility, tolerance with respect to many solvents and functional groups. However, some drawbacks greatly affect the possibility of achieving of suitable degree of control over some “polymeric” parameters which become important for specific applications. The introduction of controlled/”living” radical polymerization (CRP) techniques has then represented an opportunity for MIPs to reduce, and in some cases even to overcome, some of their limits arising from FRP. In this respect, this Ph. D. Thesis has studied how the use of RAFT polymerization, one of the most applied CRPs, can be advantageously used to syntheze MIPs. This has been done by focusing on the main characteristics of CRPs: their living and controlled nature. The living nature has been exploited during the first part of this work, which involved the synthesis of superparamagnetic molecularly imprinted nanocomposites via surface-initiated RAFT polymerization of p(EGDMA-co-MAA) on amino-modified Fe3O4 nanoparticles. The polymer grafting has been performed using an unusual stirring technique (i. E. Ultrasonication) during the polymerization step, and by testing different polymerization solvents for evaluating their effect on the composite structure. It has been observed that the grafting resulted in homogeneous polymer layers, the thickness of which could be controlled by adjusting the RAFT/radical source ratio. Moreover, the living nature of RAFT fragments has been exploited for post-functionalizing the surface of a composite particle with p(EGMP) brushes, thus demonstrating the potential of fine-tuning the particle surface properties through the living chain ends. In the second part of the thesis, an in-depth study has been performed on the effects induced by the use of controlled (RAFT) polymerization conditions on the binding behaviour and structural parameters of bulk acrylic and methacrylic MIPs and the corresponding non-imprinted polymers, synthesized by RAFT and FRP with varying cross-linking degree. This strategy actually provided scaffolds with progressively increased degree of flexibility (especially in the case of acrylics) which allowed visualize the enhancement of binding and structural differences arising from the polymerization technique. As a result, it has been observed that the use of controlled (RAFT) conditions induced, on the imprinted networks, an increased template affinity over equivalent FRPs, and it has been demonstrated that this improved affinity can be related to more homogeneous distributions of the cross-linking points achieved during RAFT polymerization. The third part presents preliminary results toward the synthesis by RAFT of individual multi-composite MIP nanosensors using enhanced Raman spectroscopy (SERS) for detection
26
Ono, Isamu. "Optimization of the Structure of Benzocyclobutene Containing Methacrylate Monomer for Controlled Radical Polymerization." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1468500945.
27
Morin, Aurélie. "Controlled radical polymerization of vinyl esters and vinyl amides : experimental and theoretical studies." Thesis, Toulouse, INPT, 2013. http://www.theses.fr/2013INPT0117/document.
Abstract:
Ces travaux de thèse portent sur la polymérisation radicalaire contrôlée (PRC) des esters et amides de vinyle. L’une des possibilités de contrôle est le piégeage dynamique réversible des chaînes radicalaires croissantes (P•) par un agent de contrôle (T) formant une espèce dormante (P─T’). La concentration en radicaux dans le milieu peut alors diminuer dramatiquement de sorte que les réactions indésirables de terminaisons soient négligeables et que le contrôle de la masse molaire des polymères soit atteint avec un faible indice de dispersité. L’utilisation de complexes métalliques, pouvant s’oxider et former une liaison métal-carbone, comme agent de piégeage des radicaux est une manière de réaliser ce contrôle. La PRC est alors appelée Polymérisation Radicalaire Contrôlée par voie Organométallique (OMRP). A ce jour, plusieurs métaux de transitions ont été utilisés avec plus ou moins de succès en OMRP. Lors de cette étude, nous avons synthétisé des complexes de cuivre(I) et testé leurs performances pour l’OMRP de l’acétate de vinyle et de l’éthylène. Nous avons également utilisé des outils de chimie théorique pour mieux comprendre pourquoi le cobalt(II) acétylacétonate est, jusqu’à aujourd’hui, le meilleur agent de contrôle pour la polymérisation de l’acétate de vinyle et des amides de vinyle. Grâce à la théorie de la fonctionnelle de densité (DFT), nous avons mis en lumière le rôle crucial de la coordination sur le cobalt des groupements carbonyles des monomères étudiésThis thesis focus on Controlled Radical Polymerization (CRP) of vinyl esters and vinyl amides. One of the possibilities to achieve this control is a dynamic reversible trapping of the growing radical chains (P•) by a controlling agent (T) to form a dormant species (P─T’). The radical concentration in the medium can be dramatically reduced so that the unwanted terminations are disfavored and polymers with controlled molecular weights and low dispersity can be obtained. A way to achieve this control is the use of metallic complexes, which can oxidize and form a metal-carbon bond, as trapping agent in the so-called Organometallic Mediated Radical Polymerization (OMRP). So far, different transition metals have been used with gretaer or smaller success. In this study, the synthesis of copper(I) complexes and their investigation for the vinyl acetate and ethylene polymerization under OMRP conditions were performed. We also used computational chemistry as a tool to better understand why the cobalt(II) acetylacetonate (Co(acac)2) has, so far, given the best results for either vinyl acetate or vinyl amides polymerization. Thanks to Density Functional Theory (DFT), the crucial role of the monomer carbonyl group coordination to cobalt was pointed out
28
Park, Sangwoo. "Electrochemically Controlled Atom Transfer Radical Polymerization and Synthesis of Polymers with Complex Architectures." Research Showcase @ CMU, 2016. http://repository.cmu.edu/dissertations/1031.
Abstract:
Atom transfer radical polymerization (ATRP) is one of the most broadly applied reversible deactivation radical polymerization (RDRP) technique that provide well-defined polymers with predetermined molecular weight (MW) and narrow molecular weight distribution (MWD). The functional polymers synthesized by ATRP showed a potential promise in the fields of biomedical applications such as smart drug delivery, tissue engineering, and diagnostic sensors. In general, conventional ATRP requires a large amount of transition metal catalysts (> 1000 parts per million (ppm) versus molar ratio of monomers) and removal of the residual catalysts is necessary for use of advanced materials in bio-applications. The advent of catalysts (re)generation from the oxidized transition metal/ligand catalysts allows for the use of ppm level of catalysts in an ATRP, and offers more environmentally benign and industrially favorable reaction conditions for the synthesis of polymers. This work mainly explores electrochemically controlled atom transfer radical polymerization (eATRP) with diminished catalysts conditions as one of many catalysts regeneration ATRP systems being examined in the past decade. This dissertation is composed of nine chapters. Chapter I reviews recent progress in electrochemically controlled chemical reaction and polymerization. Chapter II provides an in-depth study of eATRP and serves as a basis for the discussions in Chapter III on developing a simplified eATRP reaction (seATRP). Chapters II and III cover six appendices, which include related collaborations, explanations on catalysts development and characterization, polymerization mechanism, and evaluation of new polymerization procedures. Chapter IV and V address related aqueous eATRP techniques. Chapter IV details optimization of polymerization conditions for acrylamides and minimization of side reactions. Chapter V explores miniemulsion polymerization of n-butyl acrylate which requires optimization of aqueous-organic phase catalyst communication. Chapter VI addresses development of electrochemically mediated reversible addition-fragmentation chain transfer (eRAFT) polymerization of methyl methacrylate. Chapters VII to IX discuss the synthesis of copolymers with complex polymeric architectures, i.e., star polymers. Specifically in Chapter VII procedures for achieving high yield for the synthesis of stars by combining arm-first methods and eATRP to reduce initial intermolecular termination reactions. Chapter VII also contains an appendix on star synthesis by the core-first method via eATRP. Chapter VIII and IX elucidate applications of the functional star polymers. In Chapter VIII, the preparation and application of light induced crosslinkable star polymers in surface patterning are discussed and extended to biomedical applications. Lastly, Chapter IX encompasses temperature responsive surfaces, that were prepared by star polymers upon UV irradiation, as smart cell cultivate substrates.
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Bompart, Marc. "Molecularly imprinted polymers and nano-composites by free radical and controlled/living radical polymerization : applications in optical sensors." Compiègne, 2010. http://www.theses.fr/2010COMP1870.
Abstract:
Cette thèse est organisée en trois chapitres basés sur trois publications et deux manuscrits en cours de soumission. Les polymères à empreintes moléculaires (MIP) sont des récepteurs produits à façon qui sont obtenues par polymérisation en présence de molécules modèles. Le premier papier décrit l'utilisation de la spectroscopie Raman pour la détection et la quantification de molécules modèles au sein d'une particule unique de polymères a empreintes moléculaires de taille micrométrique. Les particules de polymères ont eté imprimées avec comme molécules modèles S-propranolol. Des particules de taille nanométrique et micrométrique ont été respectivement utilisées pour une analyse en masse et sur particule unique. La quantification de molécules cibles est possible sur particule unique et une limite de détection de 1µM a été obtenue sur l’analyse en masse. Le second papier décrit un capteur chimique de taille nanométrique composé d’une particule en core-shell composite. Cette particule comprend un cœur polymérique, une enveloppe inorganique composée de nanoparticules d’or pour l’exaltation du signal, recouvert d’une couche de polymères à empreintes moléculaires pour la reconnaissance. La méthode d’analyse utilisée est une exaltation su signal Raman appelé « surface enchanced Rama scattering ». Ces particules ont aussi été utilisées comme capteur avec la résonance plasmonique localisé comme méthode de transduction (papier n°3). Afin de résoudre certains problèmes associés aux polymères à empreintes moléculaires, tels que l’inhomogénéité en terme de morphologie et de distribution en site de reconnaissance, il a été suggéré d’utiliser des méthodes de polymérisations radicalaire contrôlées. Ces méthodes facilitent aussi leurs synthèses sous forme de nanomatériaux, nanocomposites et films minces. Le quatrième papier considère les récents avantages et inconvénients de ces nouvelles méthodes de polymérisation rapportés aux polymères à empreintes moléculaires. Le dernier papier décrit la première utilisation d’un récente méthode basée sur la polymérisation par transfert à l’iode (ITP), « reversible chain transfer catalyzed polymerization » (RTCP) adapté aux polymères à empreintes moléculaires. Nous décrivons un exemple de synthèse de MIP spécifiques pour la molécule propanolol par RTCP, produisant des polymères sous forme de « bulk » ou particules ayant la même capacité de reconnaissance que ceux synthétisés par polymérisation radicalaire (FRP). La RMN à l’état solide a révélée que la conversion en double liaison intramoléculaire était plus élevée dans le cas de polymères synthétisés par RTCP que par FRP, en particulier à haute concentration en amorceurThis thesis is organized in three chapters and is based on three published papers, and two manuscripts about to be submitted. Molecularly imprinted polymers (MIPs) are tailor-made synthetic receptors that are obtained by polymerization in the presence of a molecular template. The first paper describes the use of Raman spectroscopy to detect and quantify the presence of the imprinting template in single molecularly imprinted polymer microspheres. The polymers were imprinted with the Beta-blocking drugs propranolol and atenolol, and precipitation polymerization was used to obtain spherical particles. The nanoparticles were used for bulk detection whereas with micrometer-sized particles, quantitative measurements on single particles were possible. Relatively low detection limits down to 1µM have been reached for the detection of S-propranolol through bulk measurements on MIP nanoparticles. The second paper describes chemical nanosensors with a submicron core-shell composite design, based on a polymer core, a molecularly imprinted polymer (MIP) shell for selective analyte recognition, and an interlayer of gold nanoparticles for signal amplification. SERS measurements on single nanosensors yielded a detection limit of 10-7 M for the Beta-blocker propranolol, several orders of magnitude lower than on plain MIP spheres. These particles were also used as sensor materials with localized surface plasmon resonance measurements as the transduction method (Paper III), for the determination of the Beta-blocking drug propranolol. The sensors were used in suspension and were measured using a standard UV-Vis spectrophotometer. In order to solve general problems associated with MIPs, in particular their heterogeneity in terms of inner morphology and distribution of binding site affinities, it has been suggested to use modern methods of controlled/living radical polymerization for their synthesis. This also facilitates their generation in the form of nanomaterials, nanocomposites, and thin films, a strong recent trend in the field. The fourth paper reviews recent advances in the molecular imprinting area, with special emphasis on the use of controlled polymerization methods, their benefits, and current limitations. In the last paper, we have for the first time used a recently developed CRP method based on iodide mediated polymerization, reversible chain transfer catalyzed polymerization (RTCP), for the synthesis of MIPs. We show on the example of MIPs specific for the Beta-blocking drug propranolol that RTCP is compatible with MIP synthesis, both for the synthesis of bulk polymers and nanospheres, and that it yields polymers with the same binding capacity as the standard FRP method used for comparison. Solid-state NMR measurements revealed that the conversion of pendant vinyl groups was higher with RTCP than with polymers synthesized by FRP, in particular at higher initiator concentrations
30
Lin, Anna. "Nitroxide-mediated photo-polymerization." Electronic Thesis or Diss., Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0264.
Abstract:
De nos jours, la photopolymérisation est devenue un procédé important dans le domaine de la science des polymères. Cette méthode présente de nombreux avantages : la rapidité de la réaction, l‘aspect environnemental (formation limitée de composés organiques volatils et possibilité de réaction à température ambiante) ou encore un contrôle spatial et temporel. Ce mode d‘activation photochimique appliqué pendant les dernières décennies aux techniques de polymérisation radicalaire contrôlée telles que l‘ATRP, la RAFT ou la NMP permet de contrôler les propriétés des polymères mais aussi la préparation de polymères à blocs. Parmi ces techniques, la photopolymérisation contrôlée par les nitroxydes (NMP²) nécessite l‘utilisation d‘une alcoxyamine photosensible dont un groupement chromophore est porté par un nitroxyde. Dans ce manuscrit, nous présentons aussi bien la préparation d‘alcoxyamines photosensibles que les études de leurs propriétés photochimiques analysées par spectroscopie d‘absorption et par expériences de résonance paramagnétique électronique. Nous avons évalué les capacités de polymérisation des meilleurs candidats obtenus dans des conditions de NMP². Enfin, une autre méthode a été testée en effectuant une réaction de NMP² à partir d‘alcoxyamines produites par ESCP (Enhanced Spin Capturing Polymerization) ou par NMRC (Nitrone-Mediated Radical Coupling)Nowadays, photopolymerization has become an important process in the field of polymer science. This method presents several advantages such as the speed of the reaction, the environmental-friendly side (limited formation of released volatile organic compound and possibility of a reaction at room temperature) but also a spatial and temporal control. This photochemical approach applied in the past decades to controlled radical polymerization techniques such as ATRP, RAFT or NMP enable the control of polymer properties but also the preparation of block polymers. Among these techniques, the Nitroxide-Mediated Photopolymerization (NMP²) requires the use of a photosensitive alkoxyamine which has a chromophore group on the nitroxide moiety. In this manuscript, we present both the synthesis of photosensitive alkoxyamines and the studies of their photochemical properties investigated by absorption spectroscopy and by electron spin resonance experiments. We evaluated the polymerization abilities of the best obtained candidates. Finally, another approach has been tested to perform a reaction of NMP² from alkoxyamines made by ESCP (Enhanced Spin Capturing Polymerization) or via NMRC (Nitrone-Mediated Radical Coupling)
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Malere, Caroline Paganucci dos Reis. "Síntese e caracterização de padrão de poliestireno para cromatografia de permeação em gel através da polimerização via radical livre controlada mediada por radicais nitróxidos." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266829.
Abstract:
Orientador: Liliane Maria Ferrareso LonaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: A Cromatografia de Permeação em Gel ou "Gel Permeation Chromatography (GPC), também conhecida como Cromatografia de Exclusão por Tamanho ou "Size Exclusion Chromatography" (SEC) é uma das técnicas analíticas mais utilizadas para separação e caracterização de polímeros naturais e sintéticos, copolímeros e proteínas, fornecendo informações distribuição de massa molar (MWD), viscosidade intrínseca (IV) e polidispersividade (PDI). A importância de sua resposta na análise de determinado polímero se reflete em termos de sua processabilidade, uma vez que as propriedades mecânicas e químicas são drasticamente afetadas por sua massa molar média, tamanho da cadeia e distribuição. Na técnica de GPC os padrões utilizados são de primordial importância para obtenção de resultados confiáveis, pois são utilizados nas construções de curvas de calibrações necessárias para aquisição dos resultados quanti e qualitativos na técnica. Apesar da vasta utilização da técnica de GPC no Brasil, tanto em centros de pesquisa como em indústrias químicas e petroquímicas, os padrões disponíveis para comercialização são todos adquiridos no exterior, por meio de importação a altos custos. Visto a necessidade de mudança desse paradigma, este trabalho tem como objetivo desenvolver um produto nacional utilizando a polimerização via radical livre mediada por radicais nitróxidos (NMRP), também chamada "living free radical polymerization (LFRP)". O padrão escolhido para o estudo foi o poliestireno (PS), por ser ele um dos padrões mais utilizados na calibração de análise de GPC orgânico. Um dos desafios enfrentados neste trabalho foi a obtenção de polímeros com índices de polidispersividade (PDI) variando de 1 a 1,10, distribuição de massa molar (MWD) estreita e alto grau de pureza, utilizando pela primeira vez uma mistura de iniciadores no processo NMRP. A NMRP é uma técnica robusta e inovadora comparada com a polimerização iônica que é atualmente o processo empregado para obtenção de polímeros com valores de PDI muito baixos. O processo NMRP possui vantagens frente à polimerização iônica para produção de polímeros com estrutura controlada, pois nele não são necessários etapas de purificações complexas, sendo que as reações requerem menos condições estritas em relação a impurezas e temperaturas de trabalho. Este é um processo simples e barato, na qual as reações podem ser realizadas em ampolas de vidros
Abstract: Gel Permeation Chromatography, also known as Size Exclusion Chromatography, is the most employed technique to characterize macromolecules such as proteins, copolymers, natural and synthetic polymers. It provides information such as molecular weight distribution (MWD), intrinsic viscosity (IV) and polydispersity (PDI). The importance of its response reflects in terms of polymer processability once the mechanic and chemicals properties are drastically affected by the polymer average molecular weight, chain size and distribution. The standards in the GPC technique have a great importance to obtain reliable results because they are employed in calibration curves needed to acquire the quantitative and qualitative data. Despite the wide use of GPC in Brazil at research centers, chemical and petrochemical industries, all the standards available are obtained outside the country through high importation costs. To change this paradigm, this work aims to develop a national product using the pseudo-living radical polymerization or living free radical polymerization (LFRP), which is a robust and innovative technique in the polymerization science area. The standard chosen was the polystyrene, which is the most used polymer in calibration curves of organic GPC analysis. Our challenge in this work was to obtain a controlled structure polymer with polydispersity index (PDI) between 1 and 1.10, narrow molecular weight distribution (MWD) and high purity degree, using to the best of our knowledge for the first time a mixture of initiators in a NMRP process. The NMRP is a robust and innovative technique compared with the ionic polymerization that is the currently employed process to obtain polymers with very low PDI. The advantages of NMRP process over ionic polymerization to produce controlled structure polymers are that no complicated purification steps are needed, controlled radical reactions require less stringent conditions for impurities and working temperatures, it is a simple and cheaper process, where the reactions can be carried out into glass ampoules
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química
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Bergenudd, Helena. "Understanding the mechanisms behind atom transfer radical polymerization : exploring the limit of control." Doctoral thesis, KTH, Kärnkemi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-32104.
Abstract:
Atom transfer radical polymerization (ATRP) is one of the most commonly employed techniques for controlled radical polymerization. ATRP has great potential for the development of new materials due to the ability to control molecular weight and polymer architecture. To fully utilize the potential of ATRP as polymerization technique, the mechanism and the dynamics of the ATRP equilibrium must be well understood. In this thesis, various aspects of the ATRP process are explored through both laboratory experiments and computer modeling. Solvent effects, the limit of control and the use of iron as the mediator have been investigated. It was shown for copper mediated ATRP that the redox properties of the mediator and the polymerization properties were significantly affected by the solvent. As expected, the apparent rate constant (kpapp) increased with increasing activity of the mediator, but an upper limit was reached, where after kpapp was practically independent of the mediator potential. The degree of control deteriorated as the limit was approached. In the simulations, which were based on the thermodynamic properties of the ATRP equilibrium, the same trend of increasing kpapp with increasing mediator activity was seen and a maximum was also reached. The simulation results could be used to describe the limit of control. The maximum equilibrium constant for controlled ATRP was correlated to the propagation rate constant, which enables the design of controlled ATRP systems. Using iron compounds instead of copper compounds as mediators in ATRP is attractive from environmental aspects. Two systems with iron were investigated. Firstly, iron/EDTA was investigated as mediator as its redox properties are within a suitable range for controlled ATRP. The polymerization of styrene was heterogeneous, where the rate limiting step is the adsorption of the dormant species to the mediator surface. The polymerizations were not controlled and it is possible that they had some cationic character. In the second iron system, the intention was to investigate how different ligands affect the properties of an ATRP system with iron. Due to competitive coordination of the solvent, DMF, the redox and polymerization properties were not significantly affected by the ligands. The differences between normal and reverse ATRP of MMA, such as the degree of control, were the result of different FeIII speciation in the two systems.QC 20110406
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Dias, Rafael Silva. "Investigação experimental e computacional da polimerização via radical livre controlada em presença de radicais nitroxido (NMRP) utilizando-se iniciadores difuncionais." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266460.
Abstract:
Orientador: Liliane Maria Ferrareso LonaTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: Polimerização via radical livre controlada, ou Living Free Radical Polymerization (LFRP) tem recebido cada vez mais atenção como uma técnica para produção de polímeros com micro estrutura altamente controlada. Em particular, distribuições de pesos moleculares estreitas são obtidas, com polidispersidade próxima de um. Rotas usuais para obtenção de polímeros como estes têm sido polimerizações iônicas, mas elas são extremamente sensíveis a impurezas. Dentre os processos controlados, a polimerização mediada por nitróxidos (Nitroxide-Mediated Radical Polymerization-NMRP) permite a introdução de funcionalidades químicas na cadeia polimérica e apresenta como vantagens a possibilidade de polimerizações em meio aquoso, síntese de materiais híbridos, copolímeros, além de ser a rota química com menor impacto no meio-ambiente. Contudo, um dos desafios a ser enfrentado na LFRP, inclusive na NMRP, é o aumento da velocidade de reação, uma vez que as polimerizações controladas são muito mais lentas em função da existência de uma etapa de equilíbrio intrínseca. Na busca de maiores produtividades, utilizam-se temperaturas de operação ou concentração de iniciadores monofuncionais elevadas que, por conseqüência, geram polímeros com pesos moleculares mais baixos. Nos processos de polimerização convencional, o uso de iniciadores difuncionais permite o aumento da produtividade sem alterações ou mesmo com um aumento dos pesos moleculares. Sendo assim, nesta tese, foi feito um estudo experimental (polimerização em ampolas) e de simulação (desenvolvimento de modelos determinísticos e empíricos) para investigar a NMRP, no sentido de tentar reduzir o tempo gasto na polimerização, através do uso de iniciadores difuncionais. Particularmente, foram avaliadas as massas moleculares e a polidispersidade do poliestireno sintetizado usando o TEMPO (2,2,6,6, tetrametil-1-piperidinoxil) como controlador através de uma comparação com iniciadores monofuncionais (BPO e TBEC). Através de um planejamento de experimentos, determinou-se a influência da concentração do iniciador difuncional L531, da razão controlador/iniciador, e da temperatura na conversão, nos pesos moleculares e na polidispersidade e chegou-se a um modelo empírico. Foi proposto um mecanismo de reação com a derivação de equações de balanço de massa e de momentos para um reator batelada. Fez-se um bom ajuste do modelo com a estimativa de alguns parâmetros. Finalmente, desenvolveu-se uma análise de sensibilidade (dinâmica) dos parâmetros do modelo. Ambos os resultados experimentais e de simulação mostraram que foi possível obter um aumento na conversão aliado a um incremento nas massas moleculares ao se usar o iniciador difuncional L531 em relação ao monofuncionais, sendo mantido o processo controlado. Esta abordagem é inédita, pois não foi encontrado na literatura aberta nenhum tipo de polimerização radicalar controlada por nitróxidos que faça uso de iniciadores com funcionalidade superior a um.
Abstract: Controlled/Living Free Radical Polymerization (LFRP) is one of the most important techniques for production of polymeric materials with good control of the microstructure (e.g., narrow molecular weight distributions). Such properties can also be achieved via ionic polymerizations, but being a free radical polymerization process, LFRP is much less sensitive to impurities and solvents. The Nitroxide-Mediated Radical Polymerization (NMRP), as well as other LFRP processes, provides end functional polymers, and recently it has shown advantages related to polymerization in aqueous media, synthesis of hybrid materials, block copolymers, and environmental issues. However, one challenge that still must be overcome in LFRP, as well as in NMRP process, is to increase slow polymerization rates experienced due to the establishment of an intrinsic equilibrium. In order to achieve higher productivities, higher reaction temperatures or higher (monofunctional) initiator concentrations are usually used, but as a result, polymers with lower molecular weight are produced. It is well known that the use of di-functional initiators provides an enhancement of the reaction rate of conventional free radical polymerization with either no change or even an increase in molecular weight averages. Therefore, in this thesis, it was taken an experimental (polymerization in ampoules) and computational (deterministic and empirical methods) investigation of the effect of di-functional initiators on nitroxide-mediated radical polymerization with the purpose of enhancing the reaction rate. Particularly, the molecular weight development (number average molecular weight and polydispersity) of polystyrene synthesized by using TEMPO (2,2,6,6-tetramethyl-1-piperidinoxyl) as controller was evaluated by making a comparison with polymerizations using mono-functional initiators (BPO and TBEC). From the use of a design of experiments, the influence of the L531 initiator concentration, the TEMPO/initiator ratio, and the temperature on the reaction rate, molecular weights and polidispersity were determined, and an empirical model was generated. A kinetic mechanism has been proposed, from which mass balance and moment equations were derived for a batch reactor. The model was well adjusted to the experimental data with the estimation of some parameters. Lastly, a dynamic sensitivity analysis of the parameters was developed. It was shown both in experimental and simulation results that in the case of the bi-functional initiator L531, the reaction rate and molecular weights were increased when comparing to the performance of the mono-functional initiators keeping the livingness of the system. To the best of our knowledge, this is the first report of TEMPO-mediated polymerization of styrene using difunctional initiators.
Doutorado
Desenvolvimento de Processos Químicos
Doutor em Engenharia Química
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Jordan, Rainer, Tao Zhang, Yunhao Du, Felix Müller, and Ihsan Amin. "Surface-initiated Cu(0) mediated controlled radical polymerization (SI-CuCRP) using a copper plate." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-188989.
Abstract:
Surface engineering with polymer brushes has become one of the most versatile techniques to tailor surface properties of substrates for a broad variety of (bio-) technological applications. We report on a new facile approach to prepare defined and dense polymer brushes on planar substrates by surface-initiated Cu(0) mediated controlled radical polymerization (SI-CuCRP) of numerous vinyl monomers using a copper plate at room temperature. The fabrication of a variety of homo-, block, gradient and patterned polymer brushes as well as polymer brush arrays is demonstrated. The SI-CuCRP was found to be strictly surface-confined, of highly living character, proceeds remarkably fast and results in polymer brushes of very high grafting densities. The brush layer thickness can be modulated by the polymerization time or by the distance of the copper plate to the modified substrate. As the copper plate can be reused multiple times, no additional copper salts are added and only minimal amount of chemicals is needed, the simple and low-cost experimental conditions allows researchers from various fields to prepare tailored polymer brush surfaces for their needs.
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Qiao, Xiaoguang. "Synthesis of silica-polymer hybrid particles via controlled radical polymerization in aqueous dispersed media." Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10332/document.
Abstract:
Des polymères à base de méthacrylate de poly(oxyde d'éthylène) (PEOMA) avec des chaînes pendantes PEO (Mn = 300 ou 950 g mol-1) ou des copolymères de PEOMA300 et d'acide méthacrylique (AMA) ont été synthétisés par polymérisation radicalaire contrôlée par les nitroxydes en utilisant une alkoxyamine (BlocBuilder®) comme amorceur en présence de SG1 et d'une faible quantité de styrène. Les copolymères à base de PEOMA300 et d'AMA sont thermo- et pH-sensibles. Les deux types de macroalkoxyamines ont été utilisés pour amorcer la copolymérisation en émulsion du méthacrylate de n-butyle et du styrène et former, par auto-assemblage induit par la polymérisation, des particules composées de copolymères à blocs amphiphiles, en absence ou présence de particules de silice. En absence de silice, des particules stabilisées de façon stérique ou électrostérique ont été formées. La polymérisation présente les caractéristiques d'une polymérisation contrôlée avec néanmoins la formation d'une faible proportion de chaînes mortes. L'effet du pH, de la force ionique et de la nature ou de la concentration des macroalkoxyamines sur la cinétique de polymérisation et la morphologie des particules a été étudié, et des sphères, des vésicules ou des nanofibres ont été obtenues. Les macroalkoxyamines à base de PEO s'adsorbent sur la silice via la formation de liaisons hydrogène entre les chaînes PEO et les groupes silanol. La synthèse de copolymères à blocs en surface de la silice a conduit à la formation de particules hybrides de différentes morphologies (bonhomme de neige, multipodes, framboise, coeur-écorce, têtard, mille pattes) liées à la taille de la silice, au pH et à la nature du macroamorceurWater-soluble brush-type polymers composed of poly(ethylene)oxide methacrylate (PEOMA) units with PEO side groups of various chain lengths (Mn = 300 and 950 g mol-1) or of PEOMA300 with methacrylic acid (MAA) were synthesized by nitroxide-mediated polymerization using an alkoxyamine initiator (BlocBuilder®) and SG1 nitroxide in the presence of a low amount of styrene. The PEOMA300-MAA based copolymers showed a dual temperature/pH response. The two series of macroalkoxyamines were used in aqueous emulsion copolymerization of nbutyl methacrylate and styrene leading to the formation of particles composed of amphiphilic block copolymers through polymerization-induced self-assembly, in both the absence and presence of silica. The experiments performed in the absence of silica particles resulted in the formation of sterically or electrosterically stabilized latexes. The polymerization exhibited all the features of a controlled system with however the presence of a small proportion of dead chains. The effect of pH value, ionic strength and type and concentration of the macroalkoxyamine initiator on polymerization kinetics and latex morphologies was investigated. Depending on the reaction conditions, spherical particles, vesicles or nanofibers were successfully prepared. The PEO-based macroalkoxyamines were shown to adsorb on the silica surface via hydrogen bond interaction between PEO and the silanol groups. This enabled block copolymers to be generated in situ on the silica surface leading to hybrid particles with snowman, raspberry, daisy, core-shell, “tadpole-” and “centipede-” like morphologies depending on the silica particle size, pH value and type of macroinitiator
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Franco, Ivan Carlos 1976. "Modelagem matematica da polimerização via radical livre controlada usando mecanismo RAFT (transferencia de cadeia reversivel por adição-fragmentação)." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266173.
Abstract:
Orientador: Liliane Maria Ferrareso LonaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: Polimerização via radical livre controlada (CRP) tem recebido cada vez mais atenção como uma técnica para produção de polímeros com micro estrutura altamente controlada. Em particular, distribuições de pesos moleculares estreitas são obtidas, com polidispersidade muito próxima de um, sendo um campo promissor na ciência de polimerização com estruturas controladas. Um importante requisito para engenharia de polimerização e desenvolvimento de polímeros é a construção de modelos matemáticos úteis, especialmente aqueles de natureza mecanística, com validação experimental. O objetivo deste trabalho é o desenvolvimento de modelos matemáticos abrangentes para simulação de polimerização para mecanismo RAFT. Metacrilato de metila em benzeno a 60°C na presença de 2,2-cianopropil 1- pirrolecarboditioato (agente RAFT) e com AIBN como iniciador em um reator batelada será considerado como estudo. Os pesos moleculares foram calculados utilizando o método dos momentos. Uma análise paramétrica considerando o efeito da concentração de iniciador e da concentração de agente RAFT foi realizada. O modelo predito está de acordo com os dados experimentais da literatura, o que atesta sua validade para ser utilizado no controle de estruturas poliméricas obtidas no processo RAFT
Abstract: Lately, Living Free Radical Polymerization (LFRP) has been detached as a technique for the production of polymers with highly controlled microstructure. In particular, narrow distributions of molecular weights are obtained, with polydispersity values next to one. So, this technique is a promising field in the science of polymerization with controlled structures. An important requirement for engineering of polymerization and polymer development is the construction of useful mathematical models, especially those of mechanistic nature, with experimental validation. The objective of this work was to develop comprehensive mathematical models to simulate polymerization from RAFT mechanism. Methyl Methacrylate in benzene at 60°C in the presence of 2-cyanoprop-2-yl 1-pyrrolecarbodithioate (agent RAFT) and with AIBN as the initiator in a batch reactor was considered. The molecular weights have been calculated using the method of moments. A parametric analysis considering the effect of the initiator and agent RAFT concentrations was performed. Models prediction showed good agreements with experimental data from literature, what certifies its validity in being used in the control of polymeric structures in RAFT process
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química
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Wu, Lei Verfasser], Alexander [Akademischer Betreuer] Böker, and Andrij Z. [Akademischer Betreuer] [Pich. "Surface-initiated controlled radical polymerizations from silica nanoparticles / Lei Wu ; Alexander Böker, Andrij Pich." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1130590585/34.
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Wu, Lei [Verfasser], Alexander Akademischer Betreuer] Böker, and Andrij Z. [Akademischer Betreuer] [Pich. "Surface-initiated controlled radical polymerizations from silica nanoparticles / Lei Wu ; Alexander Böker, Andrij Pich." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1130590585/34.
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Lang, Andreas [Verfasser], and Mukundan [Akademischer Betreuer] Thelakkat. "Semiconductor Polymer Architectures using Click Chemistry and Controlled Radical Polymerization / Andreas Lang. Betreuer: Mukundan Thelakkat." Bayreuth : Universitätsbibliothek Bayreuth, 2011. http://d-nb.info/101923458X/34.
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Lessard, Benoît. "Advances in Nitroxide-mediated controlled radical polymerization from Poly(Methacrylate)s to perfectly alternating copolymers." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=110396.
Abstract:
Nitroxide mediated controlled radical polymerization (NMP) has been utilized since the early 1990s, as a simple and robust technique for the synthesis of various new polymeric architectures. Since the development of second generation initiators based on SG1 and TIPNO stable radicals, NMP is no longer restricted to the polymerization of just styrenics as it was initially and can now homopolymerize a plethoraof monomers such as acrylates and acrylamides. In this thesis, several advances in NMP due to these second generation initiators, were explored. The homopolymerization of methacrylates, by NMP, results inexcessive irreversible termination due to the elevated concentration of free radicals generated in the initial stages of the polymerization. However, the use of a small amount of a "controlling" comonomer can be used to control the copolymerization, as characterized by a linear increase in number average molecular weight (Mn), versus conversion (X) and a narrow molecular weight distribution (Mw/Mn < 1.5). The use of styrene ( 10 mol%) as a "controlling" comonomer for ethyl methacrylate, n-butyl methacrylate and tert-butyl methacrylate resulted in a controlled copolymerization of pseudo-"living" random copolymers characterized by a narrow molecular weight distributions (Mw/Mn = 1.2-1.5). In addition to styrene, 9-(4-vinylbenzyl)-9H-carbazole) (VBK) was used as a "controlling" comonomer for methyl methacrylate and 2-(dimethylamino)ethyl methacrylate, requiring as little as 1-2 mol% VBK relative to methacrylate, resulting in a controlled pseudo-"living" polymerization. In the second part of the thesis, NMP was utilized to control the copolymer microstructure. When using a non-equimolar feed of maleic anhydride (MA) and styrene (S), the synthesis of poly(MA-alt-S)-b-poly(S) block copolymers characterized by narrow molecular weight distributions (Mw/Mn = 1.3) where one block consisted of alternating MA and S monomers, was possible when the polymerization temperature was kept below 90 C. Finally a poly(ethylene-co-butylene)-SG12 initiator was synthesized and was used to successfully polymerize S and S/MA mixtures. The final poly(ethylene-co-butylene)-poly(MA-alt-S)2 block copolymers were tested as compatibilizers in blends with nylon-6.L'utilisation de la polymèrisation radicale contrôlée en présence de radicaux nitroxyde (NMP) a débuté vers les annèes 1990s. Cette technique est simple et robuste, portant facilement à la synthèse de diverses nouvelles architectures de polymères. Grâce au développement d'initiateurs de deuxième génération basés sur radicaux stables de SG1 et de TIPNO, l'NMP n'est plus limité à la polymérisation des styrènes et peut maintenant homopolymériser une varietée de monoméres tels que des acrylates et des acrylamides. Dans cette thèse, plusieurs développements de l'NMP dus à ces initiateurs de deuxième génération, ont été explorés. L'homopolymérisation des methacrylates, par NMP, a pour consèquence un excés de terminaisons irréversibles en raison de à la concentration élevée de radicaux libres produits au début de la polymérisation. Cependant, une petite quantité de comonomère "contrôlant" peut être utilisée pour contrôler la copolymèrisation, donnant comme résultat une augmentation linéaire de la masse molaire moyenne en nombre (Mn) avec la conversion (X) ainsi que des copolymères qui possèdent une distribution moléculaire étroite (Mw/Mn < 1.5). Le styrène ( 10 mol%) a été utilisé comme comonomère "contrôlant" pour la synthèse du méthacrylate éthylique, le méthacrylate n-butylique et le méthacrylate de tert- butyl. Dans tous les cas la copolymèrisation était contrôlée, donnant comme résultat un copolymère qui est "vivant" et qui possède une distribution moléculaire étroite (Mw/Mn = 1.2-1.5). En ajout du styrène, 9-(4-vinylbenzyl)-9H-carbazole) (VBK) a été employé comme comonomère "contr^olant" pour le méthacrylate méthylique et le méthacrylate de 2-diméthylaminoéthyle, mais cette fois exigeant que 1-2 mol% de VBK par rapport aux méthacrylates, ayant comme résultat une copolymèrisationcontr^olée et des copolymères _naux qui sont "vivants". Dans la deuxième partie de la thèse, NMP a été utilisé pour contrôler la microstructure de divers copolymères. En employant une formulation non-équimolaire d'anhydride maléique (MA) et de styrène (s), la synthèse de blocs copolymères poly(MA-alt-S)-b-poly(S) ayant une distribution moléculaire étroite (Mw/Mn = 1.3) a été réalisée lorsque la température de polymérisation était maintenue en dessous de 90C. Finalement l'initiateur poly(éthyléne-co-butyléne)-SG12 a été synthètisé et employé pour la polymèrisation de S et de mélanges de S/MA. Finalement, des copolymères en bloc poly(éthyléne-co-butyléne)-poly(MA-alt-S)2 ont été examinés comme compatibilisateur de mélanges avec le nylon-6.
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Li, Guang-Zhao. "Synthesis and application of some novel functional polymers via controlled radical polymerization and click chemistry." Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/54118/.
Abstract:
The objective of this thesis was to prepare thermoresponsive PEG-based homopolymers and copolymers by combination of cobalt-mediated catalytic chain-transfer polymerization (CCTP) and thiol-ene “click” chemistry and prepare well-defined glycopolymers via “living” polymerization and “click” chemistry. The effect of different catalysts for the nucleophilic mediated thiol-ene reaction was investigated using model compounds, both monomers and oligomers obtained by CCTP. Different catalysts, including pentylamine and hexylamine (primary amines), triethylamine (tertiary amine), and two different phosphines, dimethylphenylphosphine (DMPP) and tris(2-carboxyethyl) phosphine (TCEP), were investigated in the presence of different thiols. The optimum reaction conditions for nucleophile mediated thiol-ene click reactions were investigated. Thermoresponsive PEG-based homopolymers and copolymers of OEGMEMA obtained by CCT were modified using thiol-ene click chemistry with a variety of different functional thiol compounds to yield functional thermoresponsive polymers in high yield. The effect of different solvent systems for based catalyzed thiol-ene reaction was investigated in the presence of different functional thiols. The ATRP polymerization of TMS-PgMA and TIPS-PgMA and ROP polymerization of aliphatic polyester were investigated. A maleimide functional initiator was used in order to achieve post conjugation of nanoparticles for drug delivery. Moreover, the disulfide based bifunctional initiator was introduced into the midpoint of the polymer chain, which could break down to afford the corresponding polymer chain with thiol end group under the reducing condition. The thiol-terminated polymer was also post-functionalized via thiol-ene click chemistry. In addition, the aliphatic polycarbonate is a biocompatible and biodegradable polymer, which is widely used in medical and pharmaceutical applications. The subsequent introduction of sugar moiety to the reactive polymer chain via CuAAC click reaction and then the interactions between glycopolymers and lectins were investigated by Surface Plasmon Resonance (SPR) and Quartz Crystal Microbalance with Dissipation (QCM-D). The controlled SET-LRP polymerization of TMS-PgMA and SET-RAFT polymerization PgMA with the intact alkyne at ambient temperature were investigated. A maleimide functional initiator and CPDB, as the chain transfer agent have been employed. The introduction of maleimide moiety was to allow for post polymerization conjugation to peptides via reaction with cysteines. The subsequent introduction of sugar azides to click with the reactive polymer containing alkyne group and the glycopolymers through CuAAC was also investigated. The glycopolymer has been successfully prepared combining the SET-LRP/SET-RAFT and CuAAc click chemistry at ambient temperature.
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Saoud, Fozi. "Superparamagnetic nanoparticles for synthesis and purification of polymers prepared via controlled/"living" radical polymerization (CLRP)." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/3998.
Abstract:
Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: Living chains prepared by RAFT polymerization and NMP reactions using Z-carboxylate and Z-phosphate RAFT agents, and X-phosphate NMP initiators, were efficiently attached to the surface of magnetic nanoparticles (MNPs) and used for the separation of dead chains formed in these polymerization reactions prior to the attachment of the RAFT agents and NMP initiators to the surface of MNPs. All the living chains that attach selectively to the surface of MNPs contained RAFT or NMP functionalities, had a low polydispersity index (PDI), and could be reactivated to form new polymer extensions or block copolymers with no detectable deviation from 100% efficiency. RAFT chains prepared by RAFT polymerization using the Z-carboxylate RAFT agent and an excess of free radical initiator were also attached to the surface of MNPs and separated in the presence of an external magnetic field. Separated RAFT-functional chains contained no dead chains formed by combination or disproportionation reactions, but a substantial amount of cross-terminated by-product with a low UV absorbance at 320 nm. The cross-termination of the intermediate radical formed in the RAFT polymerization reactions was also investigated in the monomer-excluded free radical reaction model of polystyryl benzyl-(4-carboxyl dithiobenzoate) and polystyryl ethyl-2-bromoisobutyrate. The Z-carboxylate 3- and 4-arm star polymers (formed by cross-termination reactions) were then efficiently attached to the surface of MNPs and separated from the remainder of the polymer solution. They were separated from MNPs and characterized by 1H and 13C-NMR spectroscopy, and MALDI-ToF-MS. Living chains prepared by a RAFT miniemulsion polymerization reaction using Z-carboxylate RAFT agent were attached to the surface of MNPs and used for the separation of all dead chains and uncontrolled high molecular weight polymer of secondary particle formations occur during a miniemulsion polymerization reaction prior to the attachment. Separated dead chains had high PDI values and contained a significant fraction of uncontrolled high molecular weight polymer that lacked RAFT functionality. Initiator-derived chains formed in RAFT polymerization reactions of styrene (St) and methyl methacrylate (MMA) using phosphate free radical (PFR) initiator were selectively attached to the surface of MNPs and separated from R-group-derived polymer chains in the presence of an external magnetic field. All separated initiator-derived chains contained large fractions of dead chains with weak UV absorbance, and which lacked RAFT functionality, and small fractions of RAFT polymer chains. The separated initiator-derived chains had higher PDI values than the as-prepared polymer in the polymerization of St, but lower PDI values than the as-prepared polymer in the polymerization of MMA. RAFT agents attached to the surface of MNPs by the Z group were used as mediating agents for the synthesis of polymers grafted to the surface of MNPs. The polymers grafted to the surface of MNPs were separated from the solution of the free polymer by applying an external magnetic field. The amounts of the polymers grafted to the surface of MNPs greatly increased as the number of RAFT agents attached to the surface of MNPs decreased. When ethyl acetate was used as solvent, it reached 65% by weight and 50% by number of chains. Separated polymers grafted to the surface of MNPs had high PDI values and contained RAFT functionality. Investigations into the kinetics of the RAFT-mediated polymerization reaction on the surface of MNPs revealed that the polymerization reaction mediated using a RAFT agent attached by its Z group to the surface of MNPs had a faster polymerization rate than that mediated using a free Z group RAFT agent. The molecular weight of the grafted polymer increased linearly with conversion, and the reaction rate was pseudo-first-order.
AFRIKAANSE OPSOMMING: Lewende polimeerkettings, berei deur middel van RAFT-beheerde polimerisasie en NMP reaksies waarin Z-karboksilaat en Z-fosfaat RAFT-verbindings en 'n X-fosfaat NMP afsetter gebruik is, is geheg aan die oppervlaktes van magnetisenanopartikels (MNPs), en gebruik vir die skeiding van dooie kettings wat tydens die RAFT en NMP reaksies gevorm is. Alle lewende kettings wat aan die oppervlakte van die MNPs geheg is, is geskei van die oorblywende polimeeroplossing deur die aanwending van ‗n eksterne magnetise veld. Alle kettings wat selektief aan die oppervlaktes van die MNPs gekoppel is met RAFT of NMP funksionaliteit, het ‗n laë poliverspreidingswaarde (PDI) gehad en kon heraktiveer word om ‗n nuwe polimeerverlengings of blokkopolimere te vorm met geen merkbare afwyking van 100% doeltreffendheid nie. RAFT-kettings wat gedurende RAFT-polimerisasie met 'n Z-karboksilaat RAFT-agent en oormaat vrye-radikaalafsetter berei is, is ook geheg aan die oppervlaktes van MNPs en geskei in die teenwoordigheid van 'n eksterne magnetiese veld. Die geskeide RAFT-funksionele kettings het geen dooie kettings bevat nie (gevorm deur kombinasie reaksies), maar 'n aansienlike hoeveelheid ongekontroleerde hoë molekulêremassa polimeer (met lae UV absorpsie by 320 nm). Die kruis-beëindiging van die intermediêre radikaal wat gevorm is tydens die RAFT-proses is ondersoek in die monomeer-uitsluitende vrye-radikaalreaksiemodel van polistirielbensiel-4-karboksielditiobensoaat en polistirieletiel-2-bromoisobutiraat. Die Z-karboksilaat 3- en 4-arm sterpolimere (gevorm a.g.v. kruis-terminasiereaksies) is effektief geheg aan die oppervlaktes van MNPs en geskei van die res van die polimeeroplossing, en daarna gekarakteriseer met behulp van 1H en 13C KMR, en MALDI-ToF-MS. Lewende kettings, berei m.b.v. RAFT miniemulsiepolimerisasies met 'n Z-karboksilaat RAFT-agent, is geheg aan die oppervlaktes van MNPs en gebruik vir die skeiding van alle dooie kettings en sekondêre partikels wat tydens die reaksie voor die aanhegting gevorm het. Die geskeide dooie kettings wat agtergebly het, het 'n wye PDI getoon en het 'n aansienlike hoeveelheid ongekontroleerde hoë molekulêremassa polimeer, met geen RAFT-funksionaliteit nie, bevat. Afsetterafkomstigekettings wat gevorm is tydens die RAFT polimerisasiereaksies van stireen (St) en metielmetakrilaat (MMA) met 'n fosfaat-vrye vrye-radikaalafsetter is selektief geheg aan die oppervlaktes van MNPs en geskei van R-groep-afkomstige polimeerkettings in die teenwoordigheid van 'n eksterne magnetise veld. Alle geskeide afsetter-afkomstige kettings het 'n groot hoeveelheid dooie kettings gehad (met swak UV absorpsie) en met geen RAFT-funksionalilteit nie, en klein fraksies van RAFT-polimeerkettings. Die geskeide afsetter-afkomstige kettings het hoër PDI waardes gehad as die ('as-prepared') polimeer in die polimerisasie van St, maar laer PDI waardes as die ('as-prepared') polimeer in die polimerisasie van MMA. RAFT-verbindings wat aan die oppervlaktes van die MNPs geheg is deur middel van die Z-groep is as bemiddellingsagente (Eng: mediating agents) gebruik vir die sintese van polimere wat geënt is aan die oppervlakte aan MNPs. Die polimere wat aan die oppervlakte van die MNPs geënt is is geskei van die res van die polimeeroplossing deur die aanwending van ‗n eksterne magnetise veld. Die hoeveelhede van die polimere wat aan die oppervlaktes van die MNPs geënt is het sterk toegeneem namate die aantal RAFT-agente wat aan die oppervlaktes van MNPs geheg is afgeneem het. Wanneer etielasetaat as oplosmiddel gebruik is, was die waardes 55% m.b.t. gewig en 45% m.b.t. die aantal kettings. Die geskeide polimere wat aan die oppervlaktes van MNPs geënt is het hoë PDI getoon en het RAFT-funksionaliteit bevat. Die kinetika van die RAFT-beheerde polimerisasiereaksies van St, wat gebruik maak van ‗n RAFT-agent wat aan die oppervlakte van die MNPs geheg is deur middel van die Z-groep, is ook ondersoek. Die tempo van polimerisasie was vinniger in die geval waarin die RAFT-agent geheg is deur sy Z-groep aan die oppervlakte van die MNPs as die reaksie met 'n RAFT agent met 'n vrye Z-groep. Die molekulêremassas van die entpolimere het liniêr toegeneem met omsetting, en die reaksie was pseudo-eerste-orde.
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El, Achi Nassim. "Photochemical and photoredox reactions in continuous microreactors : application to cycloaddition, controlled polymerization and radical chemistry." Thesis, Lille 1, 2016. http://www.theses.fr/2016LIL10044/document.
Abstract:
Ce travail consiste à étudier différentes réactions photochimiques en dispositifs microfluidiques en utilisant la lumière UV/visible, par le biais de catalyseurs recyclables métalliques et non-métalliques, pour la synthèse organique aux applications pharmaceutiques et industrielles. En outre, l’utilisation des systèmes microfluidiques dans des chemins optiques miniaturisés de 500 µm résultant en une amélioration d’illumination. Les mesures d’actinométrie chimique confirment que ≈ 98% de la lumière émise atteint le mélange de réaction dans un réacteur fluidique Mikroglas® Dwell Device largement utilisé dans la littérature. Différentes réactions de cycloaddition [2 + 2] utilisées en synthèse totale ont été testées en utilisant un sensibilisateur sous UV. La réaction est quantitative après 2 h contre 47% après 10 h en batch. La polymérisation radicalaire contrôlée (ATRP) a été étudiée en utilisant le catalyseur photorédox éosine Y sous illumination à base de LED vertes. Six heures d'irradiations sont suffisantes pour fournir des polymères mono dispersés aux applications variables (plastiques, latex ...). Ces catalyseurs non-métalliques sont d'une importance capitale car ils sont plus respectueux de l'environnement. Former de nouvelles liaisons C-C et C-O est le cœur de la synthèse organique. L’utilisation de sources LEDs UV et d’un catalyseur photorédox nous a permis de former des produits d'addition (> 99%), à partir d’une part de sels de trifluoroborates et de TEMPO ou d’accepteurs de Michaël, d’autre part, après 2,5 min d'irradiation contre 8-24 h en batch.Ce travail montre clairement l’apport des systèmes microfluidiques pour l’accélération de réactions photochimiquesIn order to mimic nature’s highly energy efficient photosynthesis reaction, this work focuses on photochemical reactions using UV/visible light, metal based recyclable catalysts and metal free catalysts in flow to synthesize organic material that have pharmaceutical and industrial applications. The utilized microfluidic systems have small path lengths (500 μm) resulting in improved illumination. Using chemical actinometry, it was shown that ≈ 98% of the light supplied reached the reaction mixture inside the widely used Mikroglas® Dwell device. [2+2] cycloaddition, used in total synthesis, was tested in flow using a sensitizer under UV. The optimized reaction was quantitative after 2 h vs. 47% after 10 h in literature’s batch system. Metal free ATRP was assessed using the commercial Eosin Y in flow with green LEDs. Only 6 h of irradiation were enough to give narrow dispersed polymers that have wide applications (plastics, latex…). Metal free catalysts are of critical importance as they are more ecofriendly. Forming new C-C and C-O bonds is the heart of organic synthesis. Using UV LEDs and a photoredox catalyst, adducts of trifluoroborate salts with TEMPO and with Michaël acceptors were obtained (>99%) after only 2.5 min of irradiation in flow compared to 8-24 h in batch. Our results highlight the impact of miniaturization on accelerating photochemical reactions. Less time and energy usage, improved yields and strictly linear kinetic graphs are main features of flow technology. In addition, miniaturization requires less safety precautions rendering it favorable for large scale industry. This work supports considering the microfluidic technology for greener industrial systems
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Murari, Andre Rodriguez. "Desenvolvimento de um modelo matematico mais rigoroso para polimerização radicalar controlada mediada por radicais nitroxido de estireno." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266461.
Abstract:
Orientador: Liliane Maria Ferrareso LonaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: A polimerização radicalar livre controlada - LFRP ("Living Free-Radical Polimerization") tem sido alvo de muita atenção nos últimos anos, pois permite obter polímeros com uma microestrutura altamente controlada, ou seja, com uma distribuição de pesos moleculares médios estreita e polidispersidade (PDI) perto de uma unidade, e com estruturas moleculares complexas (por exemplo: copolímeros bloco puros), com diversas arquiteturas complexas e com funcionalidades variadas. A polimerização iônica também gera microestruturas controladas, contudo as condições de reação para a polimerização iônica requerem elevadas purezas, o que torna inviável economicamente suas aplicações em alguns processos industriais. A polimerização radicalar livre controlada mediada por radicais nitróxido - NMRP ("Nitroxide-Mediated Living Free-Radical Polymerization") é uma das técnicas da LFRP, sendo que é mais robusta às impurezas comparada com a polimerização iônica. Muitos pesquisadores têm desenvolvido modelos cinéticos para predizer o comportamento da NMRP, sendo que muitos deles não consideram em seus modelos os efeitos difusionais. Entretanto, seu mecanismo ainda não é totalmente conhecido. Acredita-se que existam outras reações paralelas não previstas nos mecanismos apresentados em literatura. Isso explicaria o fato de o modelo predizer conversões máximas de 100 %, enquanto que experimentalmente conversões menores são obtidas no final da reação; de alguns modelos serem insensíveis à razão do controlador/iniciador; dos modelos subestimarem os valores de pesos moleculares médios. Neste trabalho buscou-se uma compreensão maior do mecanismo cinético dos processos NMRP através do uso de um modelo matemático que considera a polimerização controlada do estireno usando TEMPO (2,2,6,6-tetrametil-1-piperidinoxil) como controlador e BPO (peróxido de benzoíla) como iniciador químico. Para isso, o problema foi abordado em três frentes: A primeira abordagem assume que existam efeitos difusionais ocorrendo no processo NMRP. Estes efeitos difusionais são extremamente importantes nas polimerizações radicalares convencionais (FRP - Free-Radical Polimerization), mas não foram considerados nos primeiros modelos da NMRP reportados na literatura. Com o passar dos tempos alguns autores começaram a considerar este efeito. Apesar dos muitos artigos publicados nessa área, ainda há muitas controvérsias sobre a existência ou não de efeitos difusionais nos processos NMRP. A primeira contribuição deste trabalho é elucidar este fato, com a proposta de novas correlações que predigam os efeitos difusionais na NMRP do estireno e que possuam embasamento teórico (teoria do volume livre). Correlações empíricas e semi-empíricas (baseadas na teoria de volume livre) usadas tanto na FRP quanto na LFRP foram testadas para NMRP do estireno em um modelo matemático da literatura. Algumas delas baseadas na teoria de volume livre foram modificadas com parâmetros estimados que melhor se ajustassem no sistema de estudo. A segunda abordagem desenvolvida neste trabalho faz um estudo paramétrico de todas as constantes cinéticas utilizadas no modelo. Foi observado que os parâmetros das constantes cinéticas divergem muito na literatura (algumas vezes apresentam ordens de grandezas diferentes). Esta segunda etapa do trabalho visa não somente um melhor ajuste do modelo, mas também identificar as etapas mais importantes e inferir sobre a possibilidade de existirem etapas não consideradas no mecanismo cinético. A terceira abordagem considera estar presente uma reação irreversível entre o controlador e o iniciador químico, etapa esta, não considerada nos modelos matemáticos apresentados na literatura. Na literatura, é descrita uma reação irreversível no início da polimerização do estireno entre o controlador TEMPO e o iniciador químico BPO. Baseado nesta informação introduziu-se um fator de eficiência o controlador - fc, análogo ao já consolidado fator de eficiência do iniciador - f, e estimou-se fc de modo a melhorar a aderência do modelo aos dados experimentais. Foi possível observar uma melhora significativa no ajuste com a introdução do fator de eficiência do controlador. Desta forma, pôde-se mostrar que reações laterais irreversíveis na etapa de iniciação são significativas. Observou-se também, que as correlações semi-empíricas baseadas na teoria do volume livre não melhoram significativamente o modelo, o que pode ser mais um indício de que os efeitos difusionais em NMRP são muito pouco expressivos, contrariando alguns trabalhos de literatura.
Abstract: Living Free-Radical Polymerization (LFRP) has been target of much attention in the last years, because it allows getting polymers with a highly controlled microstructure, with narrow distribution of the average molecular weights and polydispersity (PDI) close to unit, and with complex molecular structures (e.g. pure block copolymers), with different architectures with complex and varied functionality. Ionic polymerization also generates controlled microstructure, however the reaction conditions for ionic polymerization demand high pureness, what makes economically impracticable its the application in some industrial processes. Nitroxide Mediated Living Free Radical Polymerization (NMRP) is one of alternative techniques of the LFRP, which is more robust for impurities compared to the ionic polymerization. Many researchers have developed kinetic models that predict the behavior of the NMRP. However, its mechanism is not yet fully known. It is believed that there are other parallel reactions not foreseen in the mechanisms presented in literature. This explains the fact that the model predict conversions maximum of 100 %, whereas experimentally lower conversions are obtained at the end reaction; some models are insensitive to the controller/initiator rate; of the models under predict average molecular weights. It was intended a greater kinetic mechanism understanding of NMRP processes through the use of a mathematical model which considers the controlled polymerization of styrene using TEMPO (2,2,6,6 - tetramethyl-1-piperidinoxyl) as controller and BPO (benzoil peroxide) as a chemical initiator. Therefore, the problem has been addressed on three fronts: The first approach assumes that there are diffusional effects occurring in the NMRP process. The diffusional effects are extremely important in Free-Radical Polymerization - FRP, but were not considered in the NMRP first models reported in the literature. After a while, some authors have started to consider them. Despite the many articles published in this area, there are still many controversies over the existence or not of diffusional effects in NMRP; therefore the first contribution of this work is to elucidate this fact, with the proposed new correlations that predict the diffusional effects in NMRP of styrene with theoretical basement (the free volume theory). Empirical correlations and semi-empirical (based on the free volume theory) used both in FRP as in LFRP were tested for NMRP of styrene in a mathematical model of literature. Some of them (based in the free volume theory had been modified with new estimated parameters that better were adjusted in the study system. The second approach developed in this work makes a parametric study of all rate kinetic constants used in the model. It was observed that the kinetic constants parameters differ quite in the literature (sometimes have different magnitude orders). This second work phase aims not only a better model fit, but also identify the steps most important and infer the possibility of any steps not considered in the kinetic mechanism. The third approach considers being present a reaction between the controller and irreversible chemical initiator, this stage, not considered in the mathematical models presented in the literature. In the literature, is described a reaction irreversible in the beginning of styrene polymerization between the controller - TEMPO and chemical initiator - BPO. Based on this information, has been inserted a controller efficiency factor - fc, similar to that already consolidated factor in the initiator efficiency - f, and it was estimated in order to improve the agreement between the model and experimental data. It was possible to observe expressive agreement with experimental data using this factor - fc. In such a way, it could be shown that irreversible side reactions in the stage of initiation are significant, and that the correlations semiempirical based on the free volume theory do not improve the model significantly, which can be more one indication the diffusional effect in NMRP are very little significant, contradicting some works in literature.
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química
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Jones, Jason William. "Enhanced Architectural and Structural Regulation Using Controlled Free Radical Polymerization Techniques; Supramolecular Assemblies: Pseudorotaxanes and Polypseudorotaxanes." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/31766.
Abstract:
Due in large part to the growth and development of reliable surface characterization techniques, as well as to advances in the physical and chemical techniques used to modify surfaces, the technology of surface modification has seen rapid expansion over the past two decades. A major thrust of this research is the growth of controlled/"living" polymeric brushes from the surface of various substrates, an advance that promises to be a facile and reproducible way of altering surface properties. A unique initiator bearing ATRP (atom transfer radical polymerization), cleavage, and condensation functionalities was prepared and attached to the hydrolyzed surface of silica gel. Preliminary results indicate that control of reversibly terminated grafts of varying degrees of polymerization with polydispersity indices approaching 1.5 can be readily achieved-significant findings in the quest to design desired surface characteristics.
Important physical characteristics may also be altered by way of varying molecular topologies. In the second major research thrust, the use of self-assembly to construct such topologies in the form of pseudorotaxanes fashioned from diverse macrocycles with multifarious guest ions is discussed. While the underlying goal was to investigate and understand the mode of complexation based on such environmental factors as substituent affects and neighboring group influences, new insight was gained on the synthetic manipulation of cooperative events-events that freely occur in nature. The complexation behavior of several functionalized bis-(meta-phenylene)-32-crown-10 macrocycles with various paraquat guest moieties was. As expected, studies indicated that electron-donating substituents on the crown ether drive association, a likely result of increased p -p interactions among host and guest species. The association between a bicyclic macrocycle and dimethyl paraquat was also investigated. Not surprisingly, binding of paraquat by the bicyclic was much stronger than the binding found in analogous macrocycles. Lastly, the endgroup functionalization of poly(propyleneimine) dendrimers with two crown ether macrocycles was performed and the complexation with host-specific guests studied. Curiously, two extreme binding regimes were found: the larger 32-membered crown ether assembly displayed anti-cooperative behavior upon complexation with paraquat, while the smaller 24-membered macrocyclic system exhibited cooperative effects with 2o ammonium ions. These cooperative results are among the very first described for non-biological systems and hint at their potential use in developing highly efficient, synthetically designed supramolecular systems.Master of Science
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Nozari, Samira. "Towards understanding RAFT aqueous heterophase polymerization." Phd thesis, Universität Potsdam, 2005. http://opus.kobv.de/ubp/volltexte/2005/580/.
Abstract:
Reversible addition-fragmentation transfer (RAFT) was used as a controlling technique for studying the aqueous heterophase polymerization. The polymerization rates obtained by calorimetric investigation of ab initio emulsion polymerization of styrene revealed the strong influence of the type and combination of the RAFT agent and initiator on the polymerization rate and its profile. The studies in all-glass reactors on the evolution of the characteristic data such as average molecular weight, molecular weight distribution, and average particle size during the polymerization revealed the importance of the peculiarities of the heterophase system such as compartmentalization, swelling, and phase transfer. These results illustrated the important role of the water solubility of the initiator in determining the main loci of polymerization and the crucial role of the hydrophobicity of the RAFT agent for efficient transportation to the polymer particles. For an optimum control during ab-initio batch heterophase polymerization of styrene with RAFT, the RAFT agent must have certain hydrophilicity and the initiator must be water soluble in order to minimize reactions in the monomer phase.
An analytical method was developed for the quantitative measurements of the sorption of the RAFT agents to the polymer particles based on the absorption of the visible light by the RAFT agent. Polymer nanoparticles, temperature, and stirring were employed to simulate the conditions of a typical aqueous heterophase polymerization system. The results confirmed the role of the hydrophilicity of the RAFT agent on the effectiveness of the control due to its fast transportation to the polymer particles during the initial period of polymerization after particle nucleation. As the presence of the polymer particles were essential for the transportation of the RAFT agents into the polymer dispersion, it was concluded that in an ab initio emulsion polymerization the transport of the hydrophobic RAFT agent only takes place after the nucleation and formation of the polymer particles. While the polymerization proceeds and the particles grow the rate of the transportation of the RAFT agent increases with conversion until the free monomer phase disappears.The degradation of the RAFT agent by addition of KPS initiator revealed unambigueous evidence on the mechanism of entry in heterophase polymerization. These results showed that even extremely hydrophilic primary radicals, such as sulfate ion radical stemming from the KPS initiator, can enter the polymer particles without necessarily having propagated and reached a certain chain length. Moreover, these results recommend the employment of azo-initiators instead of persulfates for the application in seeded heterophase polymerization with RAFT agents.
The significant slower rate of transportation of the RAFT agent to the polymer particles when its solvent (styrene) was replaced with a more hydrophilic monomer (methyl methacrylate) lead to the conclusion that a complicated cooperative and competitive interplay of solubility parameters and interaction parameter with the particles exist, determining an effective transportation of the organic molecules to the polymer particles through the aqueous phase. The choice of proper solutions of even the most hydrophobic organic molecules can provide the opportunity of their sorption into the polymer particles. Examples to support this idea were given by loading the extremely stiff fluorescent molecule, pentacene, and very hydrophobic dye, Sudan IV, into the polymer particles.
Finally, the first application of RAFT at room temperature heterophase polymerization is reported. The results show that the RAFT process is effective at ambient temperature; however, the rate of fragmentation is significantly slower. The elevation of the reaction temperature in the presence of the RAFT agent resulted in faster polymerization and higher molar mass, suggesting that the fragmentation rate coefficient and its dependence on the temperature is responsible for the observed retardation.
Um neue Materialien mit außergewöhnlichen Eigenschaften zu erstellen, muss man in der Lage sein, die Struktur der Moleküle zu kontrollieren, aus denen die Materialien bestehen. Für das Maßschneidern solcher neuer Eigenschaften besitzen Polymere ein großes Potenzial: Dies sind sehr lange Moleküle, die aus einer großen Zahl von kleineren Einheiten aufgebaut sind. Proteine und DNS sind Beispiele für natürliche Polymere; Plastik und Gummi sind Beispiele für künstliche Polymere. Letztere werden üblicherweise durch das Zusammenfügen einer Reihe von kleineren Molekülen, den Monomeren, hergestellt. Schon lange versuchen Wissenschaftler, die Anordnung, Anzahl und Art dieser Monomere zu kontrollieren, die sich in der Struktur der Polymermoleküle widerspiegeln. Die gebräuchlichste Methode zur kommerziellen Produktion von Polymeren ist die so genannte freie radikalische Polymerisation. Die Strukturkontrolle durch diese Methode ist jedoch relativ schwierig und wurde maßgeblich erst im letzten Jahrzehnt entwickelt. Trotz der Existenz einiger effektiver Kontrollmethoden ist ihre industrielle Anwendung bislang sehr beschränkt, weil sie nicht für die Emulsionspolymerisation verwendbar sind. Die Emulsionspolymerisation ist die gängigste Technik in der industriellen Produktion von Polymeren. Es handelt sich dabei um ein vergleichsweise umweltfreundliches Verfahren, denn es werden keine organischen Lösungsmittel verwendet. Stattdessen dient Wasser als Lösungsmittel, in dem die Polymere in Form von kleinen, fein verteilten Partikeln vorliegen. In der Natur kommt dieses Prinzip beispielsweise in Pflanzen bei der Bildung von Kautschuk - allgemein als Latex bezeichnet - vor. Schließlich ist die Emulsionspolymerisation einfach durchzuführen: Das Produkt ist in vielen Fällen gebrauchsfertig, und es gibt viele technische Vorteile im Vergleich zu anderen Herstellungsprozessen.
Doch bevor die Probleme beim Einsatz von Kontrollmethoden in der Emulsionspolymerisation gelöst werden können, müssen erst ihre Ursachen geklärt werden. Dies ist eine unverzichtbare Vorraussetzung zum Übertragen von Forschungsergebnissen auf das tägliche Leben.
Ziel dieser Arbeit ist die Untersuchung der Probleme, die für die kontrollierte radikalische Polymerisation in Emulsion von Bedeutung sind. Die wichtigste Fragestellung in der Emulsionspolymerisation zielt auf die Löslichkeit der Reaktionskomponenten in den verschiedenen Phasen, wie z.B. in Wasser oder in den Polymerpartikeln. Die Kontrollmethode der Wahl für diese Arbeit ist "Reversibler Additions-Fragmentierungs Transfer" (RAFT). Die RAFT-Methode ist die modernste Kontrollmethode, und sie ist für viele Reaktionsbedingungen und viele Arten von Monomeren anwendbar.
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Radzinski, Scott Charles. "Synthesis of Bottlebrush Polymers Using the Grafting-Through and Transfer-To Methods." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/77574.
Abstract:
Bottlebrush polymers are interesting topologies that have become increasingly relevant in various applications including rheology modifiers, super-soft elastomers, photonic crystals, anti-fouling coatings, the in vivo delivery of therapeutic agents, and as promising substrates in lithographic printing. These macromolecules are comprised of numerous polymeric side-chains densely grafted to a polymer backbone. The densely grafted nature of bottlebrush polymers results in steric repulsion between neighboring polymer chains, forcing these macromolecules to adopt a chain-extended conformation. Although these remarkable macromolecules have a many different applications, the transformative potential of the bottlebrush polymer topology has not been realized because the synthesis of high molecular weight bottlebrush polymers is challenging. This dissertation focusses on improving the synthesis of these large macromolecules using the grafting-through strategy in the first section and the transfer-to strategy in the second section.
For the first time the effect of anchor group chemistry—the configuration of atoms linking the polymer to a polymerizable norbornene—was studied on the kinetics of ring-opening metathesis polymerization (ROMP) of macromonomers (MMs) initiated by Grubbs 3rd generation catalyst. A variance in the rate of propagation of >4-fold between similar MMs with different anchor groups was observed. This phenomenon was conserved across all MMs tested, regardless of solvent, molecular weight (MW), or repeat unit identity. Experimental and computational studies indicated that the rate differences likely resulted from a combination of varying steric demands and electronic structure among the different anchor groups. This new insight will allow others to achieve high MM conversion and prepare pure, high MW bottlebrush polymers by ROMP grafting-through.
The second section of this dissertation deals with a little studied bottlebrush synthesis technique called the transfer-to method. This method is a hybrid of the grafting-from and grafting-to approaches in which the growing polymer side chains detach from the backbone, propagate freely in solution, and then reattach to the backbone in a chain transfer step. Several parameters were investigated to determine optimal conditions for this process. This study provides for the first time a guide to use the transfer-to method to produce high purity bottlebrush polymers with controllable backbone and side chain length.Ph. D.
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Ott, Marcus [Verfasser], Markus [Akademischer Betreuer] Biesalski, and Annette [Akademischer Betreuer] Andrieu-Brunsen. "Tailor-made cellulose graft copolymers by controlled radical polymerization techniques / Marcus Ott ; Markus Biesalski, Annette Andrieu-Brunsen." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2017. http://d-nb.info/112415521X/34.
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Sidi, Zhao. "Synthesis, Characterization and High-throughput Screening of Photoiniferter/RAFT Agent for Well-controlled Radical Polymerization of Block Copolymers." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555435272696644.
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Allen, Michael H. Jr. "Imidazole-Containing Polymerized Ionic Liquids for Emerging Applications: From Gene Delivery to Thermoplastic Elastomers." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/49593.
Abstract:
Novel imidazole-containing polyelectrolytes based on poly(1-vinylimidazole) (poly(1VIM)) were functionalized with various hydroxyalkyl-substituents to investigate the influence of charge density and hydrogen bonding on nonviral DNA delivery. Copolymers with higher charge densities exhibited increased cytotoxicity, whereas increased hydroxyl concentrations remained nontoxic. DNA binding affinity increased with increased charge densities and increased hydroxyl content. Dynamic light scattering determined the copolymers which delivered DNA most effectively maintained an intermediate binding affinity between copolymer and DNA. Copolymers containing higher charge densities or hydroxyl concentrations bound DNA too tightly, preventing its release inside the cell. Copolymers with lower charge densities failed to protect the DNA from enzymatic degradation. Tuning hydrogen bonding concentration allowed for a less toxic and more effective alternative to conventional, highly charged polymers for the development of nonviral DNA delivery vehicles. The synthesis of amine-containing imidazolium copolymers functionalized with low concentrations of folic acid enabled the investigation of additional polymer modifications on nonviral gene delivery.
Functionalization of 1VIM with various hydroxyalkyl and alkyl groups and subsequent conventional free radical polymerization afforded a series of imidazolium-containing polyelectrolytes. Hydroxyl-containing homopolymers exhibited higher thermal stabilities and lower Tg's compared to the respective alkyl-analog. X-ray scattering demonstrated the polarity of the hydroxyl group facilitated solvation of the electrostatic interactions disrupting the
nanophase-separated morphology observed in the alkylated systems. Impedance spectroscopy determined hydroxyl-containing imidazolium homopolymers displayed higher ionic conductivities compared to the alkyl-containing analogs which was attributed to increased solvation of electrostatic interactions in the hydroxyl analogs.
Beyond functionalizing 1VIM monomers and homopolymers to tailor various properties, the synthesis of novel architectures in a controlled fashion remains difficult due to the radically unstable N-vinyl propagating radical. The regioisomer 4-vinylimidazole (4VIM) contains two resonance structures affording increased radical stability of the propagating radical. Nitroxide-mediated polymerization (NMP) and atom transfer radical polymerization (ATRP) failed to control 4VIM homopolymerizations; however, reversible addition-fragmentation chain transfer (RAFT) demonstrated unprecedented control. Linear pseudo-first order kinetics were observed and successful chain extension with additional 4VIM suggested preservation of the trithiocarbonate functionality.
Effectively controlling the polymerization of 4VIM enabled the design of amphoteric block copolymers for emerging applications. The design of ABA triblock copolymers with 4VIM as a high Tg supporting outer block and di(ethylene glycol) methyl ether methacrylate (DEGMEMA) as a low Tg, inner block, required the development of a new difunctional RAFT chain transfer agent (CTA). The difunctional CTA successfully mediated the synthesis of the ABA triblock copolymer, poly(4VIM-b-DEGMEMA-b-4VIM), which exhibited microphase separated morphologies. The amphoteric nature of the imidazole ring required substantially lower concentrations of outer block incorporation compared to traditional triblock copolymers to achieve similar mechanical properties and microphase separated morphologies.Ph. D.