Bibliografie tematiche / Electron-Transfer polymerization

Letteratura scientifica selezionata sul tema "Electron-Transfer polymerization"

Autore: Grafiati

Pubblicato: 25 maggio 2024

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Articoli di riviste sul tema "Electron-Transfer polymerization":

Kajiwara, Atsushi. "Characterizations of radicals formed in radical polymerizations and transfer reactions by electron spin resonance spectroscopy". Pure and Applied Chemistry 90, n. 8 (28 agosto 2018): 1237–54. http://dx.doi.org/10.1515/pac-2018-0401.

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Abstract Electron spin resonance (ESR, aka electron paramagnetic resonance, EPR) investigations have been conducted on radicals formed during radical polymerizations and provide a detailed characterization of the active radical species. Active propagating radicals can be observed during actual radical polymerizations by ESR/EPR. The chain lengths of the observed radicals were estimated by a combination of atom transfer radical polymerization (ATRP) and ESR/EPR. The structures of the chain end radicals were determined by analysis of the ESR/EPR spectra. An increase in the dihedral angles between terminal p-orbital of radical and Cβ–H bonds was observed with increasing chain lengths of methacrylate polymers. Radical transfer reactions were observed during radical polymerization of acrylates. A combination of ATRP and ESR/EPR clarified a 1,5-hydrogen shift mechanism of the radical transfer reactions using model adamantyl acrylate radicals. Penultimate unit effects were also observed. Time-resolved ESR/EPR (TR ESR) spectroscopy clarified the initiation processes of an alternating copolymerization of styrene with maleic anhydride and the copolymerization of styrene with 1,3-butadiene. Several unsolved problems in conventional radical polymerization processes have been clarified using combinations of ATRP with ESR/EPR and TR ESR. Characterization of the radicals in radical polymerizations using various ESR techniques would definitely provide interesting and useful information on conventional radical polymerizations.

Fantin, Marco, Francesca Lorandi, Armando Gennaro, Abdirisak Isse e Krzysztof Matyjaszewski. "Electron Transfer Reactions in Atom Transfer Radical Polymerization". Synthesis 49, n. 15 (4 luglio 2017): 3311–22. http://dx.doi.org/10.1055/s-0036-1588873.

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Electrochemistry may seem an outsider to the field of polymer science and controlled radical polymerization. Nevertheless, several electrochemical methods have been used to determine the mechanism of atom transfer radical polymerization (ATRP), using both a thermodynamic and a kinetic approach. Indeed, electron transfer reactions involving the metal catalyst, initiator/dormant species, and propagating radicals play a crucial role in ATRP. In this mini-review, electrochemical properties of ATRP catalysts and initiators are discussed, together with the mechanism of the atom and electron transfer in ATRP.1 Introduction2 Thermodynamic and Electrochemical Properties of ATRP Catalysts3 Thermodynamic and Electrochemical Properties of Alkyl Halides and Alkyl Radicals4 Atom Transfer from an Electrochemical and Thermodynamic Standpoint5 Mechanism of Electron Transfer in ATRP6 Electroanalytical Techniques for the Kinetics of ATRP Activation7 Electrochemically Mediated ATRP8 Conclusions

Nablo, Sam V. "Transfer coating by electron initiated polymerization". Radiation Physics and Chemistry (1977) 25, n. 4-6 (gennaio 1985): 599–608. http://dx.doi.org/10.1016/0146-5724(85)90139-6.

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Ciardelli, Francesco, Angelina Altomare, Guillermo Arribas, Giuseppe Conti e Renato Colle. "Electron transfer mechanism in olefin polymerization". Polymers for Advanced Technologies 6, n. 3 (marzo 1995): 159–67. http://dx.doi.org/10.1002/pat.1995.220060310.

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Rosen, Brad M., e Virgil Percec. "Single-Electron Transfer and Single-Electron Transfer Degenerative Chain Transfer Living Radical Polymerization". Chemical Reviews 109, n. 11 (11 novembre 2009): 5069–119. http://dx.doi.org/10.1021/cr900024j.

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Tsarevsky, Nicolay V., Wade A. Braunecker e Krzysztof Matyjaszewski. "Electron transfer reactions relevant to atom transfer radical polymerization". Journal of Organometallic Chemistry 692, n. 15 (luglio 2007): 3212–22. http://dx.doi.org/10.1016/j.jorganchem.2007.01.051.

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Rosen, Brad M., e Virgil Percec. "ChemInform Abstract: Single-Electron Transfer and Single-Electron Transfer Degenerative Chain Transfer Living Radical Polymerization". ChemInform 41, n. 11 (19 febbraio 2010): no. http://dx.doi.org/10.1002/chin.201011273.

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Jakubowski, Wojciech, e Krzysztof Matyjaszewski. "Activator Generated by Electron Transfer for Atom Transfer Radical Polymerization". Macromolecules 38, n. 10 (maggio 2005): 4139–46. http://dx.doi.org/10.1021/ma047389l.

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Paterson, Stefan M., David H. Brown, Jeremy A. Shaw, Traian V. Chirila e Murray V. Baker. "Synthesis of Poly(2-Hydroxyethyl Methacrylate) Sponges via Activators Regenerated by Electron-transfer Atom-transfer Radical Polymerization". Australian Journal of Chemistry 65, n. 7 (2012): 931. http://dx.doi.org/10.1071/ch12161.

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Activators regenerated by electron-transfer atom-transfer radical polymerization, catalyzed by tris(2-pyridylmethyl)amine/CuBr2 and Na{Cu(Gly3)}, was used to synthesize poly(2-hydroxyethyl methacrylate) sponges from 80 : 20 H2O/2-hydroxyethyl methacrylate mixtures. Polymerization-induced phase separations resulted in sponges having morphologies based on agglomerated polymer droplets. During the synthesis of poly(2-hydroxyethyl methacrylate) sponges, first-order kinetics were observed up to a maximum of ~50 % conversion regardless of the catalyst used. The morphologies of the sponges were dependent on the rate of polymerization, slower polymerization rates resulting in polymers with larger morphological features (pores and polymer droplets).

LINDEN, LARS-AKE, JERZY PACZKOWSKI, JAN F. RABEK e ANDRZEJ WRZYSZCZYNSKI. "Photodissociative and electron-transfer photoinitiators of radical polymerization". Polimery 44, n. 03 (marzo 1999): 161–76. http://dx.doi.org/10.14314/polimery.1999.161.

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Più fonti

Tesi sul tema "Electron-Transfer polymerization":

Armitage, Bruce Alan. "Photoinduced electron transfer, energy transfer and polymerization reactions in phospholipid membranes". Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/186212.

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The differential physical properties found at different depths of a phospholipid membrane permit design of systems for vectorial reactions (which are not possible in isotropic solution). In the system described in Chapter IV, a hydrophobic electron donor (triphenylbenzylborate) binds to the membrane interior while a hydrophilic electron acceptor (a cyanine dye) binds to the surface. Irradiation with red light leads to vectorial electron flow via photoinduced electron transfer (PET), as monitored by fluorescence quenching and photobleaching techniques. The PET reaction efficiency is enhanced over the case where the donor and acceptor are present in water without membranes. In that case, strong dimeric complexes are formed which reduce the efficiency of PET by enhancing nonradiative decay modes for the dye (Chapter III). Addition of a porphyrin to the membrane surface extends the sensitivity of the system to blue light (Chapter V). Excitation of the porphyrin at 417 nm and subsequent energy transfer to the cyanine trigger the same PET chemistry observed with red-light irradiation. Furthermore, the electron- and energy-transfer reactions are enhanced on polymerized, phase-separated membranes (Chapter VI). In these applications, membranes are media for chemical reactions. Membranes also make interesting substrates for chemical reactions, in this case, polymerization. A system consisting of a membrane-bound, amphiphilic cyanine dye and molecular oxygen is described in Chapter VII which effectively initiates the polymerization of vesicles upon irradiation with visible light. Potential utility in drug delivery applications is discussed.

Oyaizu, Kenʼichi. "Oxidative polymerization of diaryl disulfides based on simultaneous two-electron transfer process /". Electronic version of summary, 1995. http://www.wul.waseda.ac.jp/gakui/gaiyo/2108.pdf.

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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.

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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.

Sörensen, Nicolai. "Kinetics and Mechanism of Cu-Catalyzed Atom Transfer Radical Polymerization". Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2015. http://hdl.handle.net/11858/00-1735-0000-0023-9662-7.

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LEREBOURS, PIGEONNIERE BRIGITTE. "Phototransfert d'electron en micelles directes : polymerisation de tensioactifs, carcterisation de vesicules mixtes". Paris 6, 1987. http://www.theses.fr/1987PA066490.

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Cette etude traite des relations entre structure et reactivite de differents agregats solubles dans l'eau. Les principaux themes abordes sont: -la separation de charges photoinduites en milieu aqueux, micellaire et en presence de micelles a contreions polymerises. -la distribution des tensioactifs mixtes composant une vesicules mixte et son aptitude a favoriser la formation de petits semi conducteurs

Griveau, Lucie. "Emulsion polymerization in the presence of reactive PEG-based hydrophilic chains for the design of latex particles promoting interactions with cellulose derivatives". Thesis, Lyon, 2018. http://www.theses.fr/2018LYSE1329/document.

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Dans cette thèse, des particules de polymère fonctionnalisées en surface avec des groupes poly (éthylène glycol) (PEG) ont été synthétisées pour favoriser leur interaction avec les dérivés cellulosique via liaisons hydrogène intermoléculaires. Deux voies de synthèse ont été proposées pour obtenir ses composites cellulose/latex.La première voie est basée sur l'auto-assemblage induit par polymérisation (PISA) pour former des nanoparticules fonctionnalisées avant leur adsorption sur un substrat cellulosique. La PISA tire profit de la formation de copolymères blocs amphiphiles dans l'eau en combinant la polymérisation en émulsion avec les techniques de polymérisation radicalaire contrôlées (RDRP). Ces dernières sont utilisées pour synthétiser des polymères hydrophiles agissant à la fois comme précurseur pour la polymerization en émulsion d'un monomère hydrophobe, et comme stabilisant des particules de latex obtenues. Deux techniques de RDRP ont été étudiées : les polymérisations RAFT et SET-LRP. Des polymères hydrophiles à base de PEG de faible masse molaire ont été synthétisés en utilisant ses deux techniques qui sont ensuite utilisés pour la polymérisation d'un bloc hydrophobe dans l'eau. Le transfert de l'agent de contrôle au site de la polymérisation était difficile en utilisant la SET-LRP en émulsion, conduisant à la formation de larges particules. En utilisant la RAFT en émulsion, des particules nanométriques ont été obtenues, avec un changement morphologique observé en fonction de la taille du segment hydrophobe, puis adsorbées sur des nanofibrilles de cellulose (CNF).La seconde voie utilise la polymérisation en émulsion classique réalisée en présence de nanocristaux de cellulose (CNC) conduisant à une stabilisation Pickering des particules de polymère. L'interaction cellulose/particule est assurée grâce à l'ajout d’un comonomère à type PEG. Une organisation a été visualisé dans laquelle plusieurs particules de polymère recouvrent chaque CNC
In this thesis, polymer particles surface-functionalized with poly(ethylene glycol) (PEG) groups were synthesized to promote their interaction with cellulose derivatives via intermolecular hydrogen bond. Two synthetic routes were proposed to obtain such cellulose/latex composites.The first route was based on the polymerization-induced self-assembly (PISA) to form functionalized polymer nanoparticles prior to adsorption onto cellulosic substrate. PISA takes advantage of the formation of amphiphilic block copolymers in water by combining emulsion polymerization with reversible-deactivation radical polymerization (RDRP) techniques. The latter were used to synthesize well-controlled hydrophilic polymer chains, acting as both precursor for the emulsion polymerization of a hydrophobic monomer, and stabilizer of the final latex particles. Two RDRP techniques were investigated: reversible addition-fragmentation chain transfer (RAFT), and single electron transfer-living radical polymerization (SET-LRP). Low molar mass PEG-based hydrophilic polymers have been synthesized using both techniques, used for the polymerization of a hydrophobic block in water. The transfer of controlling agent at the locus of the polymerization was challenging for SET-LRP in emulsion conditions leading to surfactant-free large particles. Nanometric latex particles were obtained via RAFT-mediated emulsion polymerization, with morphology change from sphere to fibers observed depending on the size of the hydrophobic segment, which were then able to be adsorbed onto cellulose nanofibrils (CNFs).The second route used conventional emulsion polymerization performed directly in presence of cellulose nanocrystals (CNCs) leading to Pickering-type stabilization of the polymer particles. Cellulose/particle interaction was provided thanks to the addition of PEG-based comonomer. Original organization emerged where CNCs were covered by several polymer particles

Durbeej, Bo. "Quantum Chemical Studies of Protein-Bound Chromophores, UV-Light Induced DNA Damages, and Lignin Formation". Doctoral thesis, Uppsala University, Quantum Chemistry, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4531.

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Quantum chemical methods have been used to provide a better understanding of the photochemistry of astaxanthin and phytochromobilin; the photoenzymic repair of UV-light induced DNA damages; and the formation of lignin.

The carotenoid astaxanthin (AXT) is responsible for the colouration of lobster shell. In solution, the electronic absorption spectra of AXT peak in the 470-490 nm region, corresponding to an orange-red colouration. Upon binding to the lobster-shell protein-complex α-crustacyanin, the absorption maximum is shifted to 632 nm, yielding a slate-blue colouration. Herein, the structural origin of this bathochromic shift is investigated on the basis of recent experimental work.

The tetrapyrrole phytochromobilin (PΦB) underlies the photoactivation of the plant photoreceptor phytochrome. Upon absorption of 660-nm light, PΦB isomerizes from a C15-Z,syn configuration (in the inactive form of the protein) to C15-E,anti (in the active form). In this work, a reaction mechanism for this isomerization is proposed.

DNA photolyases are enzymes that repair DNA damages resulting from far-UV-light induced [2+2] cycloaddition reactions involving pyrimidine nucleobases. The catalytic activity of these enzymes is initiated by near-UV and visible light, and is governed by electron transfer processes between a catalytic cofactor of the enzyme and the DNA lesions. Herein, an explanation for the experimental observation that the repair of cyclobutane pyrimidine dimers (CPD) – the major type of lesion – proceeds by electron transfer from the enzyme to the dimer is presented. Furthermore, the formation of CPD is studied.

Lignin is formed by dehydrogenative polymerization of hydroxycinnamyl alcohols. A detailed understanding of the polymerization mechanism and the factors controlling the outcome of the polymerization is, however, largely missing. Quantum chemical calculations on the initial dimerization step have been performed in order to gain some insight into these issues.

Casanova, Marion. "Conception et évaluation de vecteurs polymériques d'iminium N-hétérocyclique à activité antiplasmodiale". Electronic Thesis or Diss., Aix-Marseille, 2023. http://theses.univ-amu.fr.lama.univ-amu.fr/230324_CASANOVA_795kpzkf736jdsb801go615hzgclu_TH.pdf.

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La vectorisation de médicaments a mis en exergue de réelles innovations pharmacologiques et pharmacocinétiques. Néanmoins, peu d’études originales ont été menées sur les vecteurs à visée antiparasitaire. Seuls des médicaments pour lesquels les parasites ont développé des mécanismes de résistance, ont été utilisés en vectorisation. Les conditions et coûts de préparation de ces nanoformulations sont également un frein majeur à leur future production. L’enjeu consistait donc à développer des nanovecteurs permettant la délivrance de nouvelles classes d’antiparasitaires, tout en s’appuyant sur une stratégie de synthèse « click » à la fois accessible et innovante. Dans un premier temps, le potentiel antipaludique de nouveaux sels d’iminium N-hétérocycliques a été évalué sur Plasmodium falciparum, responsable du paludisme. Les sels de bis-aminopyridiniums se sont avérés être les plus prometteurs avec des activités de l’ordre du sub-micromolaire et un mécanisme d’action original probablement lié à leurs forts pouvoirs rédox. Dans un deuxième temps, la vectorisation de ces candidats bis-aminopyridinium a été entreprise par la préparation de nanovecteurs de type conjugués polymère-médicament. Ces derniers ont été obtenus via une stratégie simple consistant en l’utilisation du bis-aminopyridinium comme initiateur de la polymérisation de son propre nanovecteur. L’étude des RSA a souligné l’importance d’un premier bloc acrylate et d’un arrangement sphérique sur l’activité. Ainsi, un système tribloc soluble, biodégradable et furtif, de tailles inferieures à 100 nm, vectorisant 5 mol% de principe actif, a permis le maintien d’une bonne activité antiplasmodiale, sans effet cytotoxique
Drug delivery has emphasised real pharmacological and pharmacokinetic advancements. Nevertheless, few in-depth and original studies have been conducted on antimalarial vectors. Only approved drugs, for which the parasites have developed resistance mechanisms, have been used in vectorization. The conditions and costs of preparation of these nanoformulations constitute a major barrier to their future production. This project aimed at developing nanovectors for the delivery of new antiparasitic drugs, while relying on a both accessible and innovative "click" synthesis strategy. First, the antimalarial efficiency of new N-heterocyclic iminium salts was evaluated on Plasmodium falciparum, responsible for malaria. Bis-aminopyridinium salts proved to be the most promising candidates with sub-micromolar antiplasmodial activities and an original mechanism of action, probably related to their strong redox properties. Secondly, the vectorization of these bis-aminopyridinium drug candidates was undertaken through preparation of polymer-drug conjugate nanovectors. The latter were obtained via a simple strategy, consisting in the use of the bis-aminopyridinium salt as polymerization initiator of its own nanovector. The SAR study underlined the need for a first acrylate block and spherical arrangements on the activity. Hence, a soluble, biodegradable, and stealth triblock system with sizes lower than 100 nm and enabling the delivery of 5 mol% of drug, showed effective antiplasmodial activity, without any cytotoxic effect

Capitoli di libri sul tema "Electron-Transfer polymerization":

Timpe, Hans-Joachim. "Photoinduced electron transfer polymerization". In Topics in Current Chemistry, 167–97. Berlin, Heidelberg: Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/3-540-52379-0_6.

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Kajiwara, Atsushi, e Mikiharu Kamachi. "Electron Spin Resonance Study of Conventional Radical Polymerization oftert-Butyl Methacrylates Using Radical Precursors Prepared by Atom Transfer Radical Polymerization". In ACS Symposium Series, 86–100. Washington, DC: American Chemical Society, 2003. http://dx.doi.org/10.1021/bk-2003-0854.ch007.

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Kajiwara, Atsushi. "Electron Spin Resonance Study of Methacrylate Radicals Generated from Purified Oligomers Prepared by Atom Transfer Radical Polymerization". In ACS Symposium Series, 111–24. Washington, D C: American Chemical Society, 2006. http://dx.doi.org/10.1021/bk-2006-0944.ch009.

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Mark, James E., Harry R. Allcock e Robert West. "Ferrocene-Based Polymers, and Additional Phosphorus- and Boron-Containing Polymers". In Inorganic Polymers. Oxford University Press, 2005. http://dx.doi.org/10.1093/oso/9780195131192.003.0010.

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Ferrocene is an inexpensive, stable molecule with an interesting and reversible electrochemistry. It is synthesized by the metal-hydrogen exchange reaction of cyclopentadiene with sodium followed by treatment of the resultant sodium cyclopentadienide anion with ferrous chloride. The high stability and electroactivity of the ferrocene molecule has prompted numerous attempts to incorporate it into polymer structures. So, too, has the inherent torsional freedom of the cyclopentadienyl groups around the iron atoms and their capacity to serve as swivel group sites. Polymerization attempts range from the addition reactions of vinylferrocene and its derivatives, to condensation reactions, ringopening polymerizations, and dendrimer assemblies. These will be considered in turn. Considerable effort in the 1970s by Pittman, George, Hayes, Korshak, and others was applied to exploring the addition polymerization of vinylferrocene to give organic polymers with pendent ferrocenyl side groups. This type of polymerization reaction has been attempted with the use of free radical, cationic, anionic, and Ziegler–Natta methods. For free radical polymerization reactions, the initiating radicals must be generated from azo-initiators because peroxides cause oxidation of the metal. In polymerizations of the type shown in reaction (2) the side group ferrocene units are the source of both the thermal stability of the product polymers and complications inherent in the free radical polymerization process. For example, electron donation from the iron atoms to a growing radical chain end can convert an active radical to an anion, which terminates the polymerization. The Fe+ center then rearranges to form a paramagnetic, ionically bound Fe(III) species. Ultimately this leads to extensive chain-transfer, limitation of the chain length, and formation of branched structures. This does not occur if the ferrocene unit is insulated from the vinyl group by a spacer unit, as in, because these monomers polymerize normally. For example, monomer gives polymers with Mn molecular weights as high as 250,000. However, the electron-transfer process outlined in reaction (2) has serious practical consequences in the free-radical polymerization of. First, directly or indirectly, it causes precipitation of the growing polymer chains until, at monomer to polymer conversions of 90% or more, all of the polymeric product is insoluble in most organic solvents.

Gorincioi, Elena, Alic Barba e Crina Vicol. "NMR spectral data - notable testimony in antioxidant interactions research: case studies of some grape metabolites". In Redox Processes with Electron and Proton Transfer, 184–98. Moldova State University, 2023. http://dx.doi.org/10.59295/prtep2023_09.

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Current research portrays the natural antioxidant systems in wine: trans- resveratrol-L-ascorbic acid and dihydroxyfumaric acid-L-ascorbic acid, in an attempt to model and elucidate plausible interactions between naturally occurring antioxidants in grapes and wine based on of the scavenging activity of 1,1-diphenyl-2-picrylhydrazyl (DPPH•) radicals by the named antioxidants and relying on 13 C and 1 H NMR spectroscopy data as a method of investigation. The evidence provided by the NMR experiments was compared with the UV-VIS spectroscopy data. For the trans- resveratrol-L-ascorbic acid system, based on the 13 C NMR method, the formation of trans-resveratrol oligomers (viniferins) was demonstrated as an effect of oxidation, in a process assisted by DPPH•. By comparing the 13 C NMR spectral results with the UV- VIS data, it was established that pronounced synergistic effects in the mentioned system are present precisely in the experimental cases for which the presence of viniferins was attested. For the dihydroxyfumaric acid-L-ascorbic acid system, the oxidation of dihydroxyfumaric acid to diketosuccinic acid, described in the literature, was not attested. Instead, through 1 H and 13 C NMR spectral studies, it was established that as a result of the interaction of dihydroxyfumaric acid with DPPH•, acid degradation occurs. The exact identification of the products of the transformation of dihydroxyfumaric acid was hindered by the secondary processes involved, with the major involvement of dihydroxyfumaric acid, namely the polymerization of acetone, triggered by dihydroxyfumaric acid, with the participation of methanol. These conclusions are supported on the basis of two-dimensional NMR experiments: 1 H/ 13 C HMBC and 1 H/ 13 C HSQC and DOSY.

Hornby, Michael, e Josephine Peach. "Reactions with nucleophiles". In Foundations of Organic Chemistry. Oxford University Press, 1993. http://dx.doi.org/10.1093/hesc/9780198556800.003.0004.

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This chapter focuses on organic reactions with nucleophiles. Nucleophiles are 'electron-rich' and have either non-bonded pairs of electrons or π-bonds; they can be anions or neutral molecules. Nucleophiles can react with species which have either positive charge or low electron density. This is the basis of many reactions, which begin with the transfer of electron density from the more electron-rich atom (in the nucleophile) to the more electron-deficient atom (in the electrophile). The chapter then looks at nucleophilic substitution reactions of haloalkanes; substitution reactions of alcohols; polymerization of cyclic ethers; the carbocation intermediate; and the competition between nucleophilic substitution and elimination. It also considers the reactions of nucleophiles with aldehydes and ketones; the reactions of nucleophiles with esters, carboxylic acids, and derivatives; the comparison of acid derivatives with aldehydes and ketones; and the comparison of the reactivities of the different types of halocompound with nucleophiles.

Okuyama, Tadashi, e Howard Maskill. "Reactions involving Radicals". In Organic Chemistry. Oxford University Press, 2013. http://dx.doi.org/10.1093/hesc/9780199693276.003.0020.

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This chapter outlines the formation of radicals by homolysis. It emphasizes that the mechanisms of radical reactions are quite different from those of polar reactions: most occur by radical chain mechanisms. The chapter then examines the stability of radicals and the radical chain reactions. It then shifts to emphasize that radical reactions are important in biology and medicine. Radicals are in fact all around us: a normal oxygen molecule is a diradical, reactive oxygen species such as superoxide anion, hydroperoxyl radical, and hydroxyl radical are believed to be implicated in the ageing process. Finally, the chapter examines radical polymerization. Radical polymerization is an important industrial process for the production of useful plastics. It then studies the formation of radical ions by single electron transfer, and their reactions as well as the electrolytic reactions.

Kumar, Munish. "Synthesis of Carbonaceous Quantum Dots". In Carbonaceous Quantum Dots: Synthesis And Applications, 20–37. BENTHAM SCIENCE PUBLISHERS, 2023. http://dx.doi.org/10.2174/9789815136265123010005.

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New class of nanocarbon materials, such as luminescent carbon quantum dots (CQDs) has gained a great deal of interest in the area of electrocatalysis, solar cells, bioimaging nanomedicine, a chemical sensor and a light-emitting diode. CQDs exhibit good physio-chemical properties, such as photoluminescence, high crystallization and good dispersibility. The rapid electron transfer, small size and superconductivity of CQDs provide the CQDs-based composite offering enhanced catalytic activity and electric conductivity. However, additional active moieties are present on the surface, which might aid in the formation of multi-component electrically activated catalysts. Additionally, the multi-component catalysts' internal interactions promote charge transfer and catalytic efficiency, both of which are essential for electrochemistry. Therefore, keeping in mind the importance of CQDs, they are synthesized on the basis of two approaches: Top-down and Bottom-up. The bulk material is reduced in size by utilizing chemical and physical processes in the top-down approach. On the contrary, in the bottom-up method, the atoms are assembled and converted into CQDs using polymerization and carbonization through a chemical reaction. Hence, in this chapter, we will discuss the synthesis techniques for CQDs, such as hydrothermal/solvothermal method, laser ablation, arc-discharge method, acidic oxidation, thermal/combustion routes, electrochemical method and microwave pyrolysis method.

Han, Chang Dae. "Rheology of Block Copolymers". In Rheology and Processing of Polymeric Materials: Volume 1: Polymer Rheology. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195187823.003.0014.

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Block copolymer consists of two or more long blocks with dissimilar chemical structures which are chemically connected. There are different architectures of block copolymers, namely, AB-type diblock, ABA-type triblock, ABC-type triblock, and AmBn radial or star-shaped block copolymers, as shown schematically in Figure 8.1. The majority of block copolymers has long been synthesized by sequential anionic polymerization, which gives rise to narrow molecular weight distribution, although other synthesis methods (e.g., cationic polymerization, atom transfer radical polymerization) have also been developed in the more recent past. Owing to immiscibility between the constituent blocks, block copolymers above a certain threshold molecular weight form microdomains (10–50 nm in size), the structure of which depends primarily on block composition (or block length ratio). The presence of microdomains confers unique mechanical properties to block copolymers. There are many papers that have dealt with the synthesis and physical/mechanical properties of block copolymers, too many to cite them all here. There are monographs describing the synthesis and physical properties of block copolymers (Aggarwal 1970; Burke and Weiss 1973; Hamley 1998; Holden et al. 1996; Hsieh and Quirk 1996; Noshay and McGrath 1977). Figure 8.2 shows schematically four types of equilibrium microdomain structures observed in block copolymers. Referring to Figure 8.2, it is well established (Helfand and Wasserman 1982; Leibler 1980) that in microphase-separated block copolymers, spherical microdomains are observed when the volume fraction f of one of the blocks is less than approximately 0.15, hexagonally packed cylindrical microdomains are observed when the value of f is between approximately 0.15 and 0.44, and lamellar microdomains are observed when the value of f is between approximately 0.44 and 0.50. Some investigators have observed ordered bicontinuous double-diamonds (OBDD) (Thomas et al. 1986; Hasegawa et al. 1987) or bicontinuous gyroids (Hajduk et al. 1994) at a very narrow range of f (say, between approximately 0.35 and 0.40) for certain block copolymers. Figure 8.2 shows only one half of the symmetricity about f = 0.5. Transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and small-angle neutron scattering (SANS) have long been used to investigate the types of microdomain structures in block copolymers.

Kumar Cheedarala, Ravi. "3D Ionic Networked Hydrophilic-Hydrophobic Nano Channeled Triboelectric Nanogenerators". In Novel Nanomaterials. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.95324.

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The power demand is increasing day by day owing to the diminishing of fossil fuel reserves on the globe. To overcome the future energy crises, there is a strong need to fulfill the energy loophole by novel technologies such as triboelectric nanogenerators to harvest miniature resources from renewable natural resources. Here, I discussed the synthesis and fabrication of novel triboelectric nanogenerators (TENGs) using highly reproducible power generators as electropositive surfaces from the monomers of naphthalene tetracarboxylic dianhydride, benzdiene diamine, and sulfonated polyimide (Bno-Spi), and modified nonwoven carbon fibers (Wcf) and polytetrafluoroethylene (PTFE) and polyvinylidene difluoride (PVDF) as electronegative TENG electrodes, respectively. Here, novel double characteristic hydrophilic and hydrophobic nano-channels concerned with Bno-Spi films were proposed through contact electrification process through ion and electron transfer by an electron-donor-acceptor complex mechanism. The proposed Bno-Spi-TENG system High triboelectric open circuit voltage 75 V (Voc) and short circuit current 1 μA (Jsc) have been achieved from Bno-Spi-TENGs, in particular, and for SO3H.Bno-Spi-TENG at 6 Hz. Besides that, we used improved knitted woven carbon fiber composite (wcf-COOH), as one of the TENGs to generate a greater open-circuit voltage (Voc), and short circuit current (Isc). Also, I aimed the contact and separation mode TENG which is using spring structure through oxidation of Wcf into Wcf-COOH followed by coupling of aniline through and one-step oxidative polymerization to get woven carbon fiber-polyaniline emraldine salt (Wcf-Pani.Es). The Wcf-PANI.Es composite film (thickness ~ 100 nm) shows the surface resistivity of 0.324 Ω m, and functions as a rubbing surface to produce charges through harvesting of energy using vertical contact-separation mode TENG. The vibrant exchanges of novel Wcf-Pani.Es, and PVDF membrane produced higher Voc of 95 V, and Isc of 180 μA, correspondingly. In specific, Wcf-Pani.Es -TENG is shown an enhancement of 498% of Voc concerning Wcf-COOH-TENG due to the availability of the Pani.Es layer. The novel Bno-Spi-TENGs and Wcf-Pani.Es are the potential candidates for fulfilling the need for improved energy harvesting devices as an alternate substantial choice for contact-separation mode TENGs.

Atti di convegni sul tema "Electron-Transfer polymerization":

TSUNOYAMA, HIRONORI, KEIJIRO OHSHIMO, ARI FURUYA, WAKANA NAKAGAWARA, FUMINORI MISAIZU e KOICHI OHNO. "INTRACLUSTER ANIONIC POLYMERIZATION INDUCED BY ELECTRON TRANSFER FROM ALKALI METAL ATOM TO UNSATURATED HYDROCARBON MOLECULES". In Clusters and Nano-Assemblies - Physical and Biological Systems. WORLD SCIENTIFIC, 2005. http://dx.doi.org/10.1142/9789812701879_0045.

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Lu, Youmei, e Toshiyuki Watanabe. "Determination of electron transfer mechanism of two-photon-induced polymerization via an efficient way: one-photon process". In Optics & Photonics 2005, a cura di Manfred Eich. SPIE, 2005. http://dx.doi.org/10.1117/12.626568.

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Gonsalves, K. E., G. Carlson, X. Chen, J. Kumar, R. Perez e M. Jose Yacaman. "Surface Functionalized Nanostructured Gold/Polymer Composites". In Organic Thin Films for Photonic Applications. Washington, D.C.: Optica Publishing Group, 1995. http://dx.doi.org/10.1364/otfa.1995.md.13.

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Nanometric gold particles were synthesized by a liquid/liquid phase-transfer reaction. Composites of these particles were prepared by free-radical polymerization of solutions of the particles in methyl methacrylate monomer. Concentrations of 1.0, 0.7, and 0.3 mg/mlwere prepared, with no noticeable agglomeration of particles during processing. PMMA/gold films showed a linear absorption peak at 530 nm, which is characteristic of nanosized gold. High-resolution electron microscopy measurement showed that the particle diameters varied from 5 to 11 nm. Degenerate four-wave mixing experiments on 10- micron films yielded a maximum value of 1.4 × 10‒11 e.s.u. for the third-order nonlinear optical susceptibility at 532 nm.

Ehrlich, J., A. Heikal, Z. Y. Hu, I. Y. S. Lee, S. R. Marder, J. W. Perry, H. Röckel e X. L. Wu. "Nonlinear Spectroscopy and Applications of Two-Photon Absorbing Molecules". In Organic Thin Films for Photonic Applications. Washington, D.C.: Optica Publishing Group, 1997. http://dx.doi.org/10.1364/otfa.1997.tha.3.

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Molecules exhibiting strong two-photon absorption hold great potential for a wide range of applications including: two-photon fluorescence microscopy, three-dimensional (3D) optical data storage, 3D microfabrication, and optical limiting. (1-4) From a fundamental point of view, knowledge of molecular two-photon spectra and structure/property relationships are also important for a more complete understanding of the third order polarizabilities of conjugated molecules. However, very little is known or understood about two-photon states and spectra of conjugated molecules or how they correlate with structure. We have observed large two-photon absorptivities in bis-donor diphenylpolyene derivatives, that appears to be correlated to simultaneous charge transfer from the end groups to the pi-conjugated bridge in the molecule. These molecules are also excellent photoexcitable electron donors that can initiate charge-transfer reactions. In initial applications of these materials we have demonstrated their use in two-photon initiation of polymerization and optical limiting.

Illera Perozo, Danny, Humberto Gómez Vega e Julian Yepes Martínez. "Synthesis and Characterization of Conjugated-Polymer/Graphene/Nanodiamond Nanocomposite for Electrochemical Energy Storage". In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-51982.

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The synthesis and characterization of Polyaniline/Graphene/ Nanodiamond Nanocomposite is reported. The resulting materials were synthetized following a polymerization in situ scheme and characterized by Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetry (TGA), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM) and Cyclic Voltammetry (CV). The effect of different loads of graphene and nanodiamond on the resulting nanocomposite was studied. Despite the presence of the host materials, the formation of Polyaniline polymer is successfully accomplished for all samples. The microstructure of the resulting materials is core-shell type with the additives being covered (core) by layers of the conjugated polymer (shell). The thermal stability of the nanocomposites is improved as confirmed by measuring an increase on the Temperature of Decomposition and the Cross-Linking Temperature compared to bare polymer. Electrochemical characterization reveals that the presence of the additives does not affect the electroactive behaviour of the matrix polymer allowing it to reversely shift from different oxidation stages. The effect of additive content on the charge transfer kinetics is discussed.

Ullah, Aman, Huiqi Wang e Rehan Pradhan. "Lipid Derived Block Copolymers as Amphiphilic Nanocarriers for Targeted Delivery". In 2022 AOCS Annual Meeting & Expo. American Oil Chemists' Society (AOCS), 2022. http://dx.doi.org/10.21748/bfgi9101.

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Amphiphilic thermoresponsive block copolymers and ABA type PEG-Lipid conjugated macromolecules have been synthesized using microwave-assisted reversible addition-fragmentation chain transfer (RAFT) polymerization and the copper-catalyzed azide-alkyne cycloaddition, commonly termed “click chemistry”, respectively. Characterization of the block copolymers and conjugates has been carried out with the help of 1H-NMR, FTIR and GPC. These copolymers and conjugates were evaluated for the encapsulation and release of drugs. Carbamazepine, an anticonvulsant drug with poor water solubility was selected to be a hydrophobic drug model in the study. The micellization, drug encapsulation and release behavior of macromolecules was investigated by dynamic light scattering (DLS), transmission electron microscope (TEM) and fluorescence spectroscopy. From the results, it has been concluded that the nanoparticles had different average sizes due to different ratio of hydrophilic contents in the block or conjugate backbone. The particle size and structure could be altered by changing the ratio of hydrophilic and hydrophobic contents. The in vitro drug encapsulations highlighted that all the drug-loaded micelles had spherical or near-spherical morphology. In vitro drug release study showed the controlled release of hydrophobic drug over a period of ~70 hours. The results indicate that there is great potential of renewable lipid-based micelle nanoparticles to be used as amphiphilic drug carriers for targeted delivery applications.

Liu, Chenzhen, Ling Ma, Zhonghao Rao e Yimin Li. "Synthesis and Characterization of Microencapsulated Phase Change Material of Magnesium Sulfate Heptahydrate/Urea Resin via Emulsion Polymerization Method". In ASME 2016 5th International Conference on Micro/Nanoscale Heat and Mass Transfer. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/mnhmt2016-6344.

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In this study, Microencapsulated phase change material (MicroPCM) was successfully synthesized by emulsion polymerization method, using magnesium sulfate heptahydrate (MSH) as core material and urea resin (UR) as shell material. The surface morphology of the MicroPCM was tested by scanning electron microscopy (SEM) and optical microscope (OM). The thermal property and particle size were investigated by differential scanning calorimetry (DSC) and laser particle size analyzer (LPA), respectively. The chemical structure of microcapsule was analyzed by Fourier-transform infrared spectroscopy (FTIR).