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Dissertationen zum Thema „Photopolymerization“
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1
Gunduz, Nazan. „Synthesis and Photopolymerization of Novel Dimethacrylates“. Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/37025.
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Four potential new monomers were prepared, all of which were structural analogues of BisGMA (2,2-bis(4-(2-hydroxy-3-methacryloxyprop-1-oxy) phenyl)propane). The synthesis of these tetrafunctional dimethacrylate monomers was based on structural modifications of Bis-GMA in the core and the side chain and required a two-step reaction. The first step was propoxylation or ethoxylation of the bisphenols and the second step was the methacrylation of the resulting products. The core structures are designated by Bis-A for isopropylidene and 6F for hexafluoropropyl. The side chain structures were designated on the basis of the pendant side chains in the glycidyl moiety as -OH, -H, and -CH3 from the epichlorohydrin, ethyleneoxide, and propyleneoxide reaction products with the bisphenols, respectively. Bis-GMA was commercially obtained and used as a standard for comparison of the experimental monomers. All the monomers were prepared by the following general procedure of propoxylation or ethoxylation of the biphenols followed by methacrylation. They were characterized by NMR, FTIR, DSC and Cone and Plate Viscometry. All the experimental monomers exhibited lower viscosities and glass transition temperatures than the control, which was attributed to the elimination of the hydrogen bonding. The monomers were photopolymerized in a differential scanning calorimetry modified with an optics assembly (DPA 7; Double Beam Photocalorimetric Accessory) to study the photo-induced crosslinking reactions. The influence of monomer structure, temperature, light intensity, and initiator concentration on the photopolymerization kinetics of ethoxylated and propoxylated dimethacrylates was investigated by isothermal DSC. The DSC curves showed a rapid increase in rate due to the Trommsdorff effect, and then a decline due to the decrease of monomer concentration and the autodeceleration effect. The monomers with lower viscosities and glass transition temperatures exhibited higher conversions of the double bonds. The final extent of conversion increased with curing temperature, light intensity and initiator concentration. The radiation intensity exponent varied from 0.68 (BisGMA) to 0.74 for the ethoxylated 6F system. The initiator exponent were varied from 0.34 (for BisGMA) to 0.44 for the propoxylated BisA system. The ratio of the reaction rate constant (kt/kp) was calculated for PropBisAdm from both steady-state and non steady-state conditions.
The effect of dilution on photopolymerization kinetics of BisGMA/triethyleneglycoldimethacrylate (TEGDMA) mixtures was also studied by isothermal photo-DSC. Dilution with TEGDMA significantly reduced the viscosity and glass transition temperatures of the mixtures due to the increase in the flexibility. The extent of polymerization increased with increasing TEGDMA and curing temperature. The calculation of ratio of rate constants (kt/kp) was also determined and the significance was discussed herein.
Master of Science
2
Bonneaud, Céline. „Synthesis and Photopolymerization of Novel Perfluoropolyalkylethers“. Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS063.
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Depuis des années, les perfluoropolyalkyléthers (PFPAEs) ont démontré de multiples facettes. Ils sont utilisés dans de nombreux secteurs et actuellement en recherche dans de multiples secteurs de pointe comme l’imagerie médicale (IRM), les réacteurs microfluidiques, les vitrimères ou encore pour des revêtements haute-performance. Ma thèse s’inscrit dans le cadre du projet européen PhotoFluo. Ce projet est partagé entre trois équipes de recherche : Trinity Western University (Langley, Canada), Politecnico di Torino (Turin, Italie) et l’Ecole Nationale Supérieure de Chimie de Montpellier. Le but du projet est de synthétiser des polymères fluorés de type PFPAEs, téléchéliques par ouverture de cycle anionique. Ensuite, ces produits sont fonctionnalisés pour obtenir des bouts de chaîne capables de réagir sous rayonnement UV. Après avoir réalisé un état de l’art de ces polymères fluorés appelés perfluoropolyalkyléthers, nous nous sommes consacrés à la synthèse et photopolymérisation d’esters α,β-insaturés en copolymérisation avec des éthers vinyliques et la synthèse et homo-photopolymérisation des maléimides ainsi que leur copolymérisation avec des éthers vinyliques. Leurs photopolymérisations respectives en tant qu’additifs ou seuls, ont permis de démontrer que ces nouveaux PFPAEs sont convertis aussi rapidement que leurs équivalents méthacrylates et même sans photoamorceur. Leur tenue thermique ainsi que leurs propriétés de surface ont été étudiées et prouvées être similaires ou supérieures aux systèmes précédents. Les maléimides ont par exemple démontré une très bonne tenue thermique pour être utilisés en tant que réacteur microfluidique à plus haute température. Dans le cadre du projet PhotoFluo, nous nous sommes aussi attardés sur la synthèse de monomères téléchéliques fluorés, la synthèse de monoépoxyde et diépoxyde pour la photopolymérisation par voie cationique, la purification par chromatographie de différents monomères photoréticulables et pour finir la synthèse de méthacrylates multifonctionnels en vue de leur photolithographie. Pour finir, afin d'élargir le champ d'application de nos perfluoropolyalkyléthers maléimides précédemment synthétisés, ces derniers ont été testés en vue d'une potentiellement application en tant que revêtement auto-cicatrisant par réaction de Diels-AlderFor years, perfluoropolyalkylethers (PFPAEs) demonstrated to be useful for a plethora of applications in numerous fields and are still under investigation for advanced technology materials for medical imaging, microfluidic devices, vitrimers or also high-performance coatings. This PhD thesis was realized in the framework of the PhotoFluo European project. This project is divided into three research teams: Trinity Western University (Langley, Canada), Politecnico di Torino (Torino, Italy) and ENSCM. The aim of the project is to synthesize telechelic PFPAEs by anionic ring-opening. Then, these products were functionalized to obtain photocurable substituents. After a review of the synthesis, properties, functionalization and applications, we devoted to the synthesis and photopolymerization of α,β-unsaturated esters in copolymerization with vinyl ethers and the synthesis and photo-homopolymerization of maleimides as well as their copolymerization with vinyl ethers. Their photopolymerization neat or as additives, demonstrated that these novel PFPAEs were able to photopolymerize as fast as their already used methacrylates homologues and even without photoinitiator. Their thermal stability as well as their surface properties were investigated and revealed to similar or superior than previous systems. For example, maleimide PFPAEs displayed an excellent thermal stability to be employed as microfluidic devices for high temperature reactions. In the PhotoFluo project, we focused on the synthesis of monoepoxy and diepoxy for the photopolymerization by cationic processes, the purification by chromatography of photocurable PFPAEs and finally, the synthesis of multifunctional methacrylate in view of photolithographic processes. To explore new horizons for our previously synthesized maleimide PFPAEs, these ones have been tested as potential self-healable coatings
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Slopek, Ryan Patrick. „In-situ Monitoring of Photopolymerization Using Microrheology“. Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7194.
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Photopolymerization is the basis of several multi-million dollar industries including films and coating, inks, adhesives, fiber optics, and biomaterials. The fundamentals of the photopolymerization process, however, are not well understood. As a result, spatial variations of photopolymerization impose significant limitations on applications in which a high spatial resolution is required.
To address these issues, microrheology was implemented to study the spatial and temporal effects of free-radical photopolymerization. In this work a photosensitive, acrylate resin was exposed to ultraviolet light, while the Brownian motion of micron sized, inert fluorescent tracer particles was tracked using optical videomicroscopy. Statistical analysis of particle motion yielded data that could then be used to extract rheological information about the embedding medium as a function of time and space, thereby relating UV exposure to the polymerization and gelation of monomeric resins.
The effects of varying depth, initiator concentration, inhibitor concentration, composition of the monomer, and light intensity on the gelation process were studied. The most striking result is the measured difference in gelation time observed as a function of UV penetration depth. The observed trend was found to be independent of UV light intensity and monomer composition. The intensity results were used to test the accuracy of energy threshold model, which is used to empirically predict photo-induced polymerization.
The results of this research affirm the ability of microrheology to provide the high spatial and temporal resolution necessary to accurately monitor the photopolymerization process. The experimental data provide a better understanding of the photo-induced polymerization, which could lead to expanded use and improved industrial process optimization. The use of microrheology to monitor photopolymerization can also aid in the development of predictive models and offer the ability to perform in-situ quality control of the process.
4
Kim, Young-Min MacGregor John Frederick. „Photopolymerization of cycloaliphatic epoxide and vinyl ether /“. *McMaster only, 2005.
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Elisseeff, Jennifer Hartt 1973. „Transdermal photopolymerization of hydrogels for tissue engineering“. Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/84773.
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Ficek, Beth Ann Scranton Alec B. „The potential of cationic photopolymerization's long lived active centers“. Iowa City : University of Iowa, 2008. http://ir.uiowa.edu/etd/280.
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7
Boddapati, Aparna. „Modeling cure depth during photopolymerization of multifunctional acrylates“. Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33934.
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The photopolymerization of multifunctional acrylates leads to the formation of a complex and insoluble network due to cross-linking. This characteristic is a useful property for stereolithography applications, where solid parts of the desired shape are cured using a pre-determined energy exposure profile. Traditionally, the required energy exposure is determined using a critical energy--depth of penetration, or Ec--Dp, model. The parameters Ec and Dp, are usually fit to experimental data at a specific resin composition and cure intensity. As a result, since the Ec--Dp model does not explicitly incorporate cure kinetics, it cannot be used for a different set of process conditions without first obtaining experimental data at the new conditions. Thus, the Ec--Dp model does not provide any insight when a new process needs to be developed, and the best processing conditions are unknown.
The kinetic model for multifunctional acrylate photopolymerization presented here is based on a set of ordinary differential equations (ODE), which can be used to predict part height versus exposure condition across varying resin compositions. Kinetic parameter information used in the model is obtained by fitting the model to double bond conversion data from Fourier Transform Infrared Spectroscopy (FTIR) measurements. An additional parameter, the critical conversion value, is necessary for determining the formation of a solid part of the desired height. The initial rate of initiation, Ri, combines all the factors that impact part height, and therefore, it is an important quantity that is required in order to find the critical conversion value. The critical conversion value is estimated using the Ri and Tgel value from microrheology measurements.
Information about network connectivity, which can be used to get properties such as molecular weight, cannot be derived from models using traditional mass-action kinetics for the cross-linking system. Therefore, in addition to modeling the reaction using the ODE based model, the results from a statistical model based on Kinetic Monte Carlo (KMC) principles are also shown here. The KMC model is applicable in situations where the impact of chain length on the kinetics or molecular weight evolution is of interest. For the present project, the detailed information from network connectivity was not required to make part height predictions, and the conversion information from the ODE model was sufficient.
The final results show that the kinetic ODE model presented here, based on the critical conversion value, captures the impact of process parameters such as initiator concentration, light intensity, and exposure time, on the final part height of the object. In addition, for the case of blanket cure samples, the part height predictions from the ODE model make comparable predictions to the Ec--Dp model. Thus, the ODE model presented here is a versatile tool that can be used to determine optimum operating conditions during process development.
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Xu, Xiaolun. „Integrated Nanoemitters on Glass-based Waveguides by Photopolymerization“. Thesis, Troyes, 2020. http://www.theses.fr/2020TROY0026.
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Les nano-émetteurs et les nanosources de lumière sont des éléments essentiels pour les dispositifs photoniques. L'une des principales exigences est la capacité d'intégrer des nano-émetteurs sur des emplacements de puces optiques spécifiques. De nombreuses approches ont été explorées pour la réalisation pratique de dispositifs photoniques évolutifs. Cependant, ces méthodes présentent certaines limites, comme des opérations compliquées, des coûts de fabrication élevés et de multiples étapes de fabrication. Cette thèse vise à explorer la faisabilité de l'intégration de nanoémetteurs basés sur des nanocomposites de polymères à points quantiques sur des substrats optiques à base de guides d'ondes en verre à échange d'ions par un processus de photopolymérisation. Nous avons fabriqué les crêtes de polymère à points quantiques de taille contrôlée sur les guides d'ondes en effectuant la photopolymérisation directe induite par le laser vert couplé au guide d'ondes avec une puissance laser et un temps d'exposition contrôlés. Nous avons réussi à fabriquer un nanocomposite de polymère à points quantiques uniques directement sur un guide d'ondes à échange d'ions grâce à la technique d'impression laser développée, basée sur la polymérisation à deux photons. L'émission couplée au guide d'ondes des points quantiques à l'intérieur du nanocomposite a été démontrée par les résultats de nos mesures de photoluminescence. Ce travail fournit une expérience expérimentale primaire pour nos travaux futursNanoemitters and nanosources of light are crucial elements for photonic devices. one of the key requirements is the ability to integrate nanoemitters onto specific optical chip locations. Many approaches have been explored for the practical realization of scalable photonic devices. However, these methods have some limitations such as complicated operations, high manufacturing costs, and multiple fabricating steps. This thesis aims to explore the feasibility of integrating nanoemitters based on quantum dots-polymer nanocomposites onto glass ion-exchanged waveguides-based optical substrates by photopolymerization process. We fabricated the size-controlled quantum dots-polymer ridges on top of waveguides by conducting the direct photopolymerization induced by the waveguide-coupled green laser with controlled laser power and exposure time. We succeeded in fabricating a single quantum dots-polymer nanocomposite directly on an ion-exchanged-waveguide by the developed laser printing technique based on two photon polymerization. The waveguide-coupled emission from the quantum dots inside the nanocomposite was demonstrated by our photoluminescence measurement results. This work provides primary experimental experience for our future work
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Slopek, Ryan Patrick. „In-situ monitoring of the mechanical properties during the photopolymerization of acrylate resins using particle tracking microrheology“. Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22657.
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Thesis (Ph. D.)--Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2008.Committee Chair: Dr. Victor Breedveld; Committee Member: Dr. Clifford Henderson; Committee Member: Dr. David Rosen; Committee Member: Dr. Peter Ludovice; Committee Member: Dr. Sai Kumar.
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Lam, Edward. „Synthesis and photochemistry of novel aromatic carbonyl photopolymerization initiators“. Thesis, Manchester Metropolitan University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.254487.
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11
Kaastrup, Kaja. „Photopolymerization-based signal amplification : mechanistic characterization and practical implementation“. Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/101507.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 124-135).
Polymerization-based signal amplification is an approach to biosensing that leverages the amplification inherent to radical polymerization to enhance signal associated with molecular recognition. This versatile technique has been implemented with a number of radical polymerization chemistries, including atom-transfer radical polymerization (ATRP), photopolymerization, reversible addition-fragmentation chain transfer polymerization (RAFT), and enzyme-mediated redox polymerization. This thesis focuses on the development of photopolymerization-based signal amplification (PBA) as a platform technology for use at the point-of-care. We sought to build a mechanistic understanding of the system, specifically examining the effects of non-ideal binding reactions and oxygen. One of the greatest barriers to wider implementation of polymerization-based signal amplification is the susceptibility of radical polymerization reactions to oxygen inhibition. Oxygen reacts with initiating and propagating radicals to form peroxy radicals that are unreactive towards propagation, and thus have the effect of terminating the reaction. Chapter 2 describes the development of an air-tolerant monomer solution that allows interfacial photopolymerization reactions to proceed under ambient conditions in as little as 35 seconds where previous implementations of PBA required inert gas purging to remove oxygen and reaction times of 20 minutes or longer. We showed that the inclusion of submicromolar concentrations of eosin, the photoinitiator, in the monomer solution mitigated the effects of oxygen. The ability to perform these reactions under ambient conditions increases their clinical utility by simplifying the procedure and by eliminating purging gases that might be detrimental in some biological applications, specifically those involving cells. Intrigued by eosin's ability to overcome over 1000-fold excess of oxygen, we performed spectroscopic measurements in order to elucidate the mechanisms underlying eosin's resistance towards oxygen inhibition. A dual-monitoring system for measuring eosin consumption and monomer conversion was used to corroborate the hypothesized regeneration of eosin in the presence of oxygen (Chapter 3). This required the development of a method for analyzing absorbance data for polymerizing hydrogels. We further examined the photoactivation kinetics of the eosin/tertiary amine system and the effect of oxygen using absorbance spectroscopy and kinetic modeling (Chapter 4). The spectroscopic investigation revealed that, in addition to the previously postulated reactions in which eosin is regenerated by oxygen, additional reactions between oxygen and eosin in its triplet state and semireduced form occur and must be taken into account. The formation and consumption of the semireduced species informed the construction of a kinetic model, for which the importance of considering the reaction between triplet state eosin and the tertiary amine as two separate steps was clearly demonstrated. Transitioning away from an examination of the amplification chemistry, we next considered the molecular recognition event, exploring the concept of the amplification threshold by investigating the impact of the binding affinity of the molecular recognition event on the limit of detection (Chapter 5). We showed that improvements in binding affinity enhance detection sensitivity. A mass action kinetics based model was used to accurately predict experimental findings and identify the key parameters for predicting the performance of PBA reactions: surface capture probe density, incubation time, concentration and binding affinity of the target molecule. We evaluated the commonly proposed strategy of developing polymeric macrophotoinitiators for improving the sensitivity of photopolymerization-based signal amplification reactions (Chapter 6). Building on earlier work, in which solubility limits were encountered coupling eosin and neutravidin to a poly (acrylic acid-co-acrylamide) backbone, we synthesized a more water-soluble polymeric macrophotoinitiator based on a generation 7 poly (amidoamine) dendrimer scaffold. Although the solubility was improved, a new quenching limitation was identified, demonstrating the complexity of designing polymeric macrophotoinitiators that incorporate eosin as the photoinitiator. In lieu of viable photoinitiator alternatives to eosin, we concluded that future efforts to design polymeric macrophotoinitiators should include features that increase the distance between eosin molecules. We used photopolymerization-based signal amplification to selectively encapsulate a target population of cells in a co-culture (Chapter 7). PBA allows for the selective growth of an immunoprotective hydrogel only at the surfaces of the labeled cells, even in closely contacted cell aggregates. The hydrogel protects the cells against subsequent lysis, allowing for nucleic acid extraction from the unlabeled cells without the need for cell sorting. Finally, we consider the vast, unexplored parameter space for photopolymerization-based signal amplification, surveying alternative photoinitiation chemistries, new approaches to signal interpretation, and future applications.
by Kaja Kaastrup.
Ph. D.
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Leigh, Braden Lynn. „Engineering surfaces using photopolymerization to improve cochlear implant materials“. Diss., University of Iowa, 2018. https://ir.uiowa.edu/etd/6176.
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Cochlear implants (CIs) help to restore basic auditory function in patients who are deaf or have profound hearing loss. However, CI patients suffer from limited voice and tonal perception due to spatial separation between the stimulating CI electrode and the receptor spiral ganglion neurons (SGNs). Directed regeneration of proximate SGN axons may improve tonal performance and implant fidelity by decreasing the spatial separation between the CI electrode and the neural receptor. Additionally, fibrous scar tissue formation on the surface of implanted electrodes further decreases tonal perception through current attenuation and spreading resulting in late-term hearing loss. Thus, designing surfaces that induce favorable responses from neural tissues will be necessary in overcoming signal resolution barriers. In this work, the inherent spatial and temporal control of photopolymerization was used to functionalize surfaces with topographical and biochemical micropatterns that control the outgrowth of neural and other cell types. First, laminin, a cell adhesion protein was patterned using a photodeactivation process onto methacrylate polymer surfaces and was shown to direct the growth of spiral ganglion neurons (SGN), the primary auditory neural receptors. These protein patterns could even overcome low amplitude/high periodicity competing topographical cues. Additionally, glass substrates were patterned with linear zwitterionic polymers and fibroblasts, astrocytes, and Schwann cells all showed dramatically decreased cell adhesion on 100 µm precocity patterns. Further, SGN neurites showed excellent alignment to these same patterns. Next, poly(dimethyl siloxane) (PDMS) was coated with a crosslinked zwitterionic thin film using a single step photografting/photopolymerization process to covalently bind the hydrogel to PDMS. These coated surfaces showed dramatically lower levels of protein, cell, and bacterial adhesion. Finally, zwitterionic hydrogels were strengthened by changing the concentration of poly(ethylene glycol) diacrylate (PEGDA) and 2-hydroxyethyl methacrylate (HEMA) in the formulation. The direct relationship between changing zwitterionic hydrogel formulation to strengthen the hydrogel and the anti-fouling properties were established. The fundamental understanding and design of cochlear implant materials described herein serves as a foundation for the development of next generation neural prosthetics.
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Barbosa, Valeria do Carmo. „Estudo da fotopolimerização e degradação de um oligomero uretano acrilado alifatico para aplicação em revestimentos para madeira“. [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/267146.
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Orientador: Lucia Helena Innocentini MeiDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
Made available in DSpace on 2018-08-14T08:41:32Z (GMT). No. of bitstreams: 1 Barbosa_ValeriadoCarmo.pdf: 1009354 bytes, checksum: 5a59ac0da1d7f49b216506cc60cdc9e6 (MD5) Previous issue date: 2008
Resumo: Vernizes obtidos por tecnologia de cura ultravioleta têm um grande campo de aplicação em revestimentos para madeira, sendo por isto bastante usada na Indústria Moveleira. Além disto, esta tecnologia é hoje importante do ponto de vista ambiental por ser considerada uma tecnologia limpa, já que sua formulação é livre de solvente, sendo considerada zero VOC [1, 2]. Sendo assim, esta tecnologia tem sofrido um grande avanço tecnológico, com o propósito de garantir revestimentos cada vez mais nobres e de melhor qualidade. Para isto buscam-se um aprimoramento das matérias-primas utilizadas nestas formulações, os oligômeros, monômeros e fotos-iniciadores. Além de matérias-primas, também processos de cura adequados são necessários para obter a excelência em acabamentos com tecnologia ultravioleta. Sendo assim este trabalho mostra a técnica de infravermelho, FT-IR, como uma poderosa ferramenta para avaliar e quantificar processos de cura para tecnologia ultravioleta [3].
Abstract: Coatings that use technology of ultraviolet radiation (UV) cure have a big applicaton Field in wood recovering and are widely used in the furnitire industry. Besides that from the environmental point of view this technology is very important nowadays and the main reason is that the UV coatings formulations are free of solvent and considered zero VOC [1, 2]. Because of it, this technology has been having a great addvence, with the purpose of garantee films more and more noble and of higher quality. For this the raw mterials present in these formulations, the oligomers, monomers and photoinitiatos, are constantly being improved. Besides the raw materials, adequate cure process are necessary to obtain the best results in this technology. This work shows the infrared technic, FT-IR, as a powerful tool to evaluate and quantify the UV curing process[3].
Universidade Estadual de Campi
Ciencia e Tecnologia de Materiais
Mestre em Engenharia Química
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Tucker, Lucas J. „Liquid crystalline holography the effect of various additives on photopolymerization /“. Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2006. http://proquest.umi.com/login?COPT=REJTPTU0NWQmSU5UPTAmVkVSPTI=&clientId=3739.
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O'Brien, Allison K. „The impact of oxygen on photopolymerization kinetics and polymer structure“. Diss., Connect to online resource, 2005. http://wwwlib.umi.com/dissertations/fullcit/3165809.
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NOE', CAMILLA. „Make it greener: Exploring novel biobased materials in photopolymerization processes“. Doctoral thesis, Politecnico di Torino, 2022. http://hdl.handle.net/11583/2962960.
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Zhao, Xiayun. „Process planning for thick-film mask projection micro stereolithography“. Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28097.
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Akgün, Ertan [Verfasser], und J. [Akademischer Betreuer] Hubbuch. „Nanoscale Polymeric Particles via Aerosol-Photopolymerization / Ertan Akgün. Betreuer: J. Hubbuch“. Karlsruhe : KIT-Bibliothek, 2015. http://d-nb.info/1067496904/34.
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Denmark, Daniel Jonwal. „Photopolymerization Synthesis of Magnetic Nanoparticle Embedded Nanogels for Targeted Biotherapeutic Delivery“. Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6827.
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Conventional therapeutic techniques treat the patient by delivering a biotherapeutic to the entire body rather than the target tissue. In the case of chemotherapy, the biotherapeutic is a drug that kills healthy and diseased cells indiscriminately which can lead to undesirable side effects. With targeted delivery, biotherapeutics can be delivered directly to the diseased tissue significantly reducing exposure to otherwise healthy tissue. Typical composite delivery devices are minimally composed of a stimuli responsive polymer, such as poly(N-isopropylacrylamide), allowing for triggered release when heated beyond approximately 32 °C, and magnetic nanoparticles which enable targeting as well as provide a mechanism for stimulus upon alternating magnetic field heating. Although more traditional methods, such as emulsion polymerization, have been used to realize these composite devices, the synthesis is problematic. Poisonous surfactants that are necessary to prevent agglomeration must be removed from the finished polymer, increasing the time and cost of the process. This study seeks to further explore non-toxic, biocompatible, non-residual, photochemical methods of creating stimuli responsive nanogels to advance the targeted biotherapeutic delivery field. Ultraviolet photopolymerization promises to be more efficient, while ensuring safety by using only biocompatible substances. The reactants selected for nanogel fabrication were N-isopropylacrylamide as monomer, methylene bisacrylamide as cross-linker, and Irgacure 2959 as ultraviolet photo-initiator. The superparamagnetic nanoparticles for encapsulation were approximately 10 nm in diameter and composed of magnetite to enable remote delivery and enhanced triggered release properties. Early investigations into the interactions of the polymer and nanoparticles employ a pioneering experimental setup, which allows for coincident turbidimetry and alternating magnetic field heating of an aqueous solution containing both materials. Herein, a low-cost, scalable, and rapid, custom ultraviolet photo-reactor with in-situ, spectroscopic monitoring system is used to observe the synthesis as the sample undergoes photopolymerization. This method also allows in-situ encapsulation of the magnetic nanoparticles simplifying the process. Size characterization of the resulting nanogels was performed by Transmission Electron Microscopy revealing size-tunable nanogel spheres between 50 and 800 nm by varying the ratio and concentration of the reactants. Nano-Tracking Analysis indicates that the nanogels exhibit minimal agglomeration as well as provides a temperature-dependent particle size distribution. Optical characterization utilized Fourier Transform Infrared and Ultraviolet Spectroscopy to confirm successful polymerization. When samples of the nanogels encapsulating magnetic nanoparticles were subjected to an alternating magnetic field a temperature increase was observed indicating that triggered release is possible. Furthermore, a model, based on linear response theory that innovatively utilizes size distribution data, is presented to explain alternating magnetic field heating results. The results presented here will advance targeted biotherapeutic delivery and have a wide range of applications in medical sciences like oncology, gene delivery, cardiology and endocrinology.
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Rudraraju, Anirudh V. „Digital data processing and computational design for large area maskless photopolymerization“. Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/52930.
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Large Area Maskless Photopolymerization (LAMP) is a novel additive manufacturing technology currently being developed at Georgia Tech in collaboration with the University of Michigan at Ann Arbor and PCC Airfoils. It is intended for the fabrication of integrally cored ceramic molds for the investment casting of precision components such as high-pressure turbine blades. This dissertation addresses the digital data processing and computational design needs for this technology. Several data processing schemes like direct slicing, STL slicing, post-processing schemes like error checking, part placement and tiling etc. were developed in order to enable the basic functionality of the LAMP process. A detailed overview of these schemes and their implementation details are given in this dissertation. Several computational schemes to improve the quality and accuracy of parts produced through the LAMP process were also implemented. These include a novel volume deviation based adaptive slicing method to adaptively slice native CAD models, a gray scaling and dithering approach to reduce stair stepping effect on downward facing surfaces and a preliminary experimental study to characterize the side curing behavior of the LAMP photo-curable suspension for pre-build image compensation. The implementation details and a discussion of the results obtained using these schemes are given. A novel approach for addressing the “floating island” problem encountered in additive manufacturing was also developed. The need for supports specific to the kind of parts being built through LAMP is evaluated and a support generation strategy different from the previously reported approaches in the literature is presented. Finally, a few novel film cooling schemes that are extremely challenging to fabricate using existing manufacturing technologies but possible to fabricate using LAMP are chosen and analyzed for their cooling performance. It is shown that such novel schemes perform much better in cooling the blade surface than the conventionally implemented schemes and hence this final component of work gives a better appreciation of the impact LAMP technology has in disrupting the state of the art in turbine blade manufacturing and truly taking the blade designs to the next level.
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Nath, Shukantu Dev. „FABRICATION AND PERFORMANCE EVALUATION OF SANDWICH PANELS PRINTED BY VAT PHOTOPOLYMERIZATION“. OpenSIUC, 2021. https://opensiuc.lib.siu.edu/theses/2883.
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Sandwich panels serve many purposes in engineering applications. Additive manufacturing opened the door for easy fabrication of the sandwich panels with different core structures. In this study, additive manufacturing technique, experiments, and numerical analysis are combined to evaluate the mechanical properties of sandwich panels with different cellular core structures. The sandwich panels having honeycomb, re-entrant honeycomb, diamond, square core topologies are printed with the vat photopolymerization technique. Uniaxial compression testing is performed to determine the compressive modulus, strength, and specific strength of these lightweight panels. Elasto-plastic finite element analysis having good similarities with the experimental results provided a preview of the stress distribution of the sandwich panels under applied loading. The imaging of the tested samples showed the fractured regions of the cellular cores. Dynamic mechanical analysis of the panels provided scope to compare the performance of panels and solid materials with the variation of temperature. Sandwich panels with the diamond structure exhibit better compressive properties and specific strength while the re-entrant structure offers high energy absorption capacity. The sandwich structures provided better thermo-mechanical properties than the solid material. The findings of this study offer insights into the mechanical properties of sandwich panels printed with vat photopolymerization technique which can benefit a wide range of engineering applications.
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Eom, Ho Seop. „Photopolymerizations of multicomponent epoxide and acrylate/epoxide hybrid systems for controlled kinetics and enhanced material properties“. Diss., University of Iowa, 2011. https://ir.uiowa.edu/etd/2488.
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Cationic photopolymerization of multifunctional epoxides is very useful for efficient cure at room temperature and has been widely used in coatings and adhesives. Despite excellent properties of the final cured polymers, cationic photopolymerizations of epoxides have seen limited application due to slow reactions (relative to acrylates) and brittleness associated with a highly crosslinked, rigid network. To address these issues, two reaction systems were studied in this thesis: photoinitiated cationic copolymerizations of a cycloaliphatic diepoxide with epoxidized elastomers and acrylate/epoxide hybrid photopolymerizations. Oligomer/monomer structures, viscosity, compositions, and photoinitiator system were hypothesized to play important roles in controlling photopolymerizations of the epoxide-based mixtures. A fundamental understanding of the interplay between these variables for the chosen systems will provide comprehensive guidelines for the future development of photopolymerization systems comparable to the epoxide-based mixtures in this research.
For diepoxide/oligomer mixtures, the observed overall enhancement in polymerization rate and ultimate conversion of the cycloaliphatic diepoxide was attributed to the activated monomer mechanism associated with hydroxyl terminal groups in the epoxidized oligomers. This enhancement increased with increasing oligomer content. The mixture viscosity influenced the initial reactivity of the diepoxide for oligomer content above 50 wt.%. Real-time consumption of internal epoxides in the oligomers was successfully determined using Raman spectroscopy. Initial reactivity and ultimate conversion of the internal epoxides decreased with increasing the diepoxide content. This trend was more pronounced for the oligomer containing low internal epoxide content. These results indicate that the reactivity of the hydroxyl groups is higher toward cationic active centers of the diepoxide than those of the internal epoxides in the oligomers. These conclusions are consistent with physical property results. The enhanced fracture toughness and impact resistance were attributed to multimodal network chain-length distribution of copolymers containing the oligomer content between 70% and 80%.
For acrylate/epoxide hybrid mixtures, diacrylate oligomers significantly suppressed reactivities of cycloaliphatic mono/diepoxides, which was attributed to high mixture viscosity and highly crosslinked acrylate network. In this case, the dual photoinitiator system did not favor the epoxide reaction. Depending on the monovinyl acrylate secondary functionalities, enhanced reactivity and ultimate conversion of the diepoxide were attributed to a combined effect of a reduced viscosity and the radical-promoted cationic polymerization associated with the dual photoinitiator. The retarded and inhibited diepoxide reactivities with ether and urethane secondary groups were attributed to solvation and nucleophilicity/basicity effects, respectively. The influence of the diepoxide on the acrylate reactivity was attributed to dilution and polarity effects. In this case, high concentration of the free-radical photoinitiator is required for the dual photoinitiator system. Physical properties of hybrid polymers also varied with acrylate structures and monomer composition. Dynamic modulation methods were proposed to enhance the diepoxide reactivity and final properties in the presence of urethane acrylates.
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Ibrahim, Ahmad. „Development of photoinitiating systems for free radical Photopolymerization usable for laser Imaging“. Thesis, Mulhouse, 2011. http://www.theses.fr/2011MULH4082.
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Le sujet de thèse sur lequel je travaille depuis trois ans est l’étude et le développement des systèmes photoamorceurs pour des applications holographiques. Ce travail a lieu en collaboration avec l’équipe BMS (Bayer Material Science) de Bayer-Leverkusen (Allemagne). Mes études se sont limitées aux systèmes utilisables avec une source d’irradiation appartenant à la partie visible du spectre électromagnétique de la lumière (400 nm – 700 nm).Parmi les différents types des réactions de polymérisation, nous avons choisi la polymérisation radicalaire. L’étape cruciale dans cette réaction réside dans la génération des radicaux qui amorcent la réaction. Ces derniers sont formés par transformation, via absorption de lumière, d’un composé photosensible. La formation de ces espèces est en général en compétition avec plusieurs processus de désactivation. Les polymérisations radicalaires sont en particulier fortement inhibées par l’oxygène de l’air. Pour réduire l’effet de l’oxygène et pour avoir des conditions comparables à ceux appliqués dans l’industrie, nos échantillons ont été préparés en utilisant la technique laminée (l’échantillon est mis entre deux films de polypropylène). [...]The subject of the thesis I have been working on for three years is the study and development of photoinitiating systems for holographic applications. This work takes place in collaboration with the BMS (Bayer Material Science) team from Bayer Leverkusen (Germany). My studies have been limited to systems used with a radiation source belonging to the visible part of the electromagnetic spectrum of light (400 nm - 700 nm). Among the different types of polymerization reactions, we chose the radical polymerization. The critical step in this reaction is the generation of radicals which initiate the reaction. These are formed by transformation via absorption of light of a photosensitive compound. The formation of these species is generally in competition with several deactivation process. [...]
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Wutticharoenwong, Kosin. „BIO-BASED REACTIVE DILUENTS AND THIOL-ENE PHOTOPOLYMERIZATION FOR ENVIRONMENTALLY BENIGN COATINGS“. University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1194282497.
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Rathi, Pankaj Jaiprakash. „Theoretical Modeling of Morphology Development in Blends of Semicrystalline Polymers Undergoing Photopolymerization“. University of Akron / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1251397199.
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Forney, Bradley Steven. „Controlled polymer nanostructure and properties through photopolymerization in lyotropic liquid crystal templates“. Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/2495.
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Incorporating nanotechnology into polymers has tremendous potential to improve the functionality and performance of polymer materials for use in a wide range of biomedical and industrial applications. This research uses lyotropic liquid crystals (LLCs) to control polymer structure on the nanometer scale in order to improve material properties. The overall goal of this research is to establish fundamental methods of synthesizing polymers with controlled nanostructured architectures in order to understand and utilize useful property relationships that result from the organized polymer morphologies. This work aims to establish a fundamental understanding of the reaction conditions needed to control polymer nanostructure and determine the benefits of organized polymer network structures on mechanical and transport properties.
The synthesis of nanostructured polymers for improved material performance has utilized LLCs and photopolymerization kinetics to direct polymer structure. Self-assembled LLC phases provide a useful template that may be used as a photopolymerization platform to control polymer morphology on the nanometer size scale. Photopolymerization kinetics were used as a tool to examine the thermodynamics and phase structure evolution that occurs during the polymerization reaction. Additionally, several methods were developed to control polymer morphology and prevent loss of LLC order that can occur during polymerization. LLCs were also used to generate nanocomposite polymers with two distinct polymer networks to impart improvements in material properties. Other useful property relationships including increases in mechanical integrity, greater diffusive transport, and larger water uptake were established in this research.
Finally, the LLC templating process was applied to solve performance problems associated with stimuli-sensitive polymer materials. Dramatic improvements in the response rate, dynamic range, and mechanical properties were achieved using LLCs and photopolymerization to control polymer nanostructure. This work has established fundamental tools that can be used to understand and control the evolution of polymer structure during the polymerization reaction in order to improve polymer properties. Ultimately, the enhanced properties generated by the nanostructured polymer network can be used to improve the functionality of polymers.
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Kim, Soon Ki. „Advanced clay nanocomposites based on in situ photopolymerization utilizing novel polymerizable organoclays“. Diss., University of Iowa, 2012. https://ir.uiowa.edu/etd/2917.
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Polymer nanocomposite technology has had significant impact on material design. With the environmental advantages of photopolymerization, a research has recently focused on producing nanocomposites utilizing inexpensive clay particles based on in situ photopolymerization. In this research, novel polymerizable organoclays and thiol-ene photopolymerization have been utilized to develop advanced photopolymer clay nanocomposites and to overcome several limitations in conventional free radical photopolymers. To this end, factors important in nanocomposite processes such as monomer composition, clay dispersion, and photopolymerization behavior in combination with the evolution of ultimate nanocomposite properties have been investigated. For monomer-organoclay compositions, higher chemical compatibility of components induces enhanced clay exfoliation, resulting in photopolymerization rate increases due to an amplified clay template effect. Additionally, by affecting the stoichiometric ratio between thiol and acrylate double bond in the clay gallery, thiolated organoclays enhance thiol-ene copolymerization with increased final thiol conversion while acrylated organoclays encourage acrylate homopolymerization. In accordance with the reaction behavior, incorporation of thiolated organoclays makes polymer chains more flexible with decreased glass transition temperature due to higher formation of thio-ether linkages while adding acrylated organoclays significantly increases the modulus. Photopolymer nanocomposites also help overcome two major drawbacks in conventional free radical photopolymerization, namely severe polymerization shrinkage and oxygen inhibition during polymerization. With addition of a low level of thiol monomers, the oxygen inhibition in various acrylate systems can be overcome by addition of only 5wt% thiolated organoclay. The same amount of polymerizable organoclay also induces up to 90% decreases in the shrinkage stress for acrylate or thiol-acrylate systems. However, nonreactive clays do not reduce the stress substantially and even decreases the polymerization rate in air. Additionally, the clay morphology and polymerization behavior are closely related with evolution of ultimate nanocomposite performance. Use of polymerizable organoclay significantly improves overall toughness of nanocomposites by increasing either modulus or elongation at break based on the type of polymerizable organoclay, which demonstrates the promise of this technology as a modulation and/or optimization tool for nanocomposite properties.
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Haraldsson, Klas Tommy. „Fabrication of polymeric microfluidic devices via photocurable liquid monomers“. Doctoral thesis, Stockholm : Fibre and Polymer Technology, Department of Chemical Engineering and Technology, Royal Institute of Technology (KTH), 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-466.
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Ajiboye, Gbenga I. „Industrially relevant epoxy-acrylate hybrid resin photopolymerizations“. Thesis, University of Iowa, 2012. https://ir.uiowa.edu/etd/3558.
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Photopolymerization of epoxy-acrylate hybrid resins takes advantages of inherent properties present in the free-radical and cationic reactions to reduce oxygen inhibition problems that plague free-radical reactions. Similarly, the combined reaction mechanisms reduce moisture sensitivity of the cationic reactions. Despite the advantages of epoxy-acrylate hybrid resins, problems persist that need to be addressed. For example, low conversion and polymerization rate of the epoxides are a problem, because the fast acrylate conversion prevents the epoxide from reaching high conversion. Controlling phase separation is challenging, since two moieties with different properties are reacting. The physical properties of the polymer will be impacted by the availability of different moieties. High shrinkage stress results from the acrylate moiety, causing buckling and cracking in film and coating applications.
The overall goal of this study is to use the fundamental knowledge of epoxy-acrylate hybrid resins to formulate industrially viable polymers. In order to achieve this goal, the study focuses on the following objectives: (I) determine the apparent activation energy of the hybrid monomer METHB, (II) increase epoxide conversion and polymerization rate of hybrid formulations, and (III) control physical properties in epoxy-acrylate hybrid resins. In order to increase the epoxide conversion and rate of polymerization, the sensitivity of epoxides to alcohol is used to facilitate the activated monomer (AM) mechanism and induce a covalent bond between the epoxide and acrylate polymers through the hydroxyl group. It is hypothesized that if the AM mechanism is facilitated, epoxide conversion will increase. As a result, the resins can be tailored to control phase separation and physical properties, and shrinkage stress can be reduced.
In pursuit of these objectives, the hybrid monomer METHB was polymerized at temperatures ranging from 30°C to 70°C to obtain apparent activation energy of 23.49 kJ/mol for acrylate and 57 kJ/mol for epoxide moeities. Then, hybrid systems pairing hydroxyl-containing acrylates with epoxides were formulated to promote the faster AM mechanism. Monomer composition was changed in the presence of hydroxyl-containing acrylate, and initiators were carefully selected in order to control phase separation. The conversion of acrylate and epoxide was monitored in real time by Raman spectroscopy. The physical and mechanical properties were monitored using dynamic mechanical analysis. Epoxide conversion and rate of polymerization in epoxide-acrylate hybrid monomer systems were shown to increase through the introduction of a hydroxyl group on the meth/acrylate monomer, taking advantage of the faster AM mechanism. In addition, this covalent bond linking the epoxide network to the meth/acrylate polymer chains resulted in little or no phase separation and a reduction of the Tg for the hybrid polymer compared to the neat epoxide.
Fundamental knowledge gained from this research will enable the use of epoxy-acrylate hybrid resins in variety of applications. For instance, shrinkage may be reduced in dental fillings, noise and vibration problems in aircraft and other machinery may be controlled, and photopolymerization cost could be reduced in thin film applications.
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Conrad, Matthew. „Experimental investigations and theoretical modeling of large area maskless photopolymerization with grayscale exposure“. Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45965.
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Large Area Maskless Photopolymerization (LAMP) is a technology being developed to fabricate integrally-cored ceramic molds for the investment casting of turbine airfoils. In LAMP, ultraviolet (UV) light in the form of bitmap images is projected from a spatial light modulator (SLM) onto a photocurable ceramic material system (PCMS). Exposed and unexposed regions are determined through black and white portions of the bitmaps, respectively. UV light induces photopolymerization and the formation of an insoluble solidified network. Three-dimensional structures are built layer-by-layer through sequential application and curing of PCMS layers of 100 micron thickness. To date, ceramic molds fabricated using LAMP have been successfully implemented in investment casting of single-crystal turbine airfoils without internal cooling schemes. Two particularly important challenges for the fabrication of airfoil molds with internal cooling passages are: (a) fabrication of unsupported structures in the mold geometry and; (b) mitigation of internal stresses that arise during layer-by-layer build-up due to volumetric shrinkage during photopolymerization. Unsupported geometries arise in nearly every cored airfoil mold and often in a location where support structures cannot be easily removed after fabrication. Internal stresses generated by volumetric shrinkage can lead to cracking during binder burnout (BBO), sintering and casting. This thesis aims to simultaneously address these challenges through the investigation of grayscale exposure to control the degree of monomer conversion during photopolymerization of single and multiple layers. The effective intensity of the UV light incident on the monomer system can be reduced by selectively turning off pixels within the nominally "white" or "on" regions of the projected bitmaps, effectively producing an exposure with a lower light intensity. In an effort to reduce internal stresses in the mold, the grayscale exposure can be tuned to create regions of uncured or partially cured monomer within the mold geometry to reduce the connectivity between cured regions and thus reduce the net effect of volumetric shrinkage. Grayscale exposure can also be used to generate support structures with a low degree of polymerization to create a gel state beneath and surrounding the unsupported segments of the mold, which can be washed away after completion of mold fabrication. In order to successfully utilize grayscale techniques in LAMP, the cure depth must be predicted. This is accomplished through cure depth measurements at different exposure times to develop a "working curve." In addition, the degree of monomer conversion and its relation to cure depths resulting from grayscale exposure must be understood. Measurements of the degree of conversion are obtained through Fourier Transform Infrared spectroscopy (FTIR). Empirical models are developed and compared to theoretical predictions. Also, the scattering length pixelation model is introduced as a technique to predict the light intensity distribution within the PCMS for exposure patterns at multiple length scales. Results from these grayscale investigations are then applied to LAMP and the effectiveness of grayscale to fabricate unsupported geometries and internal stresses from volumetric shrinkage is discussed.
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De, Paz-Simon Héloise. „Sol-gel photopolymerization of inorganic precursors and application for mesoporous silica films elaboration“. Thesis, Mulhouse, 2013. http://www.theses.fr/2013MULH6112/document.
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Alors que le procédé sol-gel a été fortement étudié il existe peu d’études concernant le procédé sol-gel photoinduit. Le principe repose sur la libération in situ d’espèces acides ou basiques photogénérées capables d’amorcer les réactions d’hydrolyse et de condensation caractéristiques du procédé sol-gel. L’alternative photoinduite est particulièrement adaptée pour préparer des films minces et possède de nombreux avantages tel qu’une formulation de départ stable, sans solvant et photolatente ainsi que des vitesses de réactions plus importantes. À partir de précurseurs inorganiques simples, nous avons dans un premier temps réalisé une étude mécanistique et cinétique de ce procédé en catalyse acide. Puis l’influence de différents paramètres physiques, chimiques et photochimiques sur les vitesses de réactions a été évaluée. Une comparaison avec un système similaire en catalyse basique a aussi été réalisée.Dans un second temps, nous nous sommes intéressés à appliquer ce procédé photoinduit pour la préparation de films de silice mésoporeuse. Un tensioactif de type copolymère tribloc a été ajouté au précurseur inorganique de départ. La faisabilité d’une approche photochimique à partir de formulation sans eau ni solvant a d’abord été étudiée, des films mésoporeux ont été obtenus. Puis, nous nous sommes intéressés à la compréhension des 2 mécanismes interdépendants : le mécanisme d’assemblage du tensioactif et la condensation du réseau inorganique. Par la suite, le système a été optimisé pour aboutir à un contrôle précis de la structure et de la taille des pores. Enfin, une dernière étape a consisté à éliminer la partie organique (pour libérer la porosité) grâce à l’UVWhereas sol-gel process has been extensively studied almost no papers concerning photoinduced sol-gel process subsists. This later is based on in situ generation of acids or basics species able of initiating hydrolysis and condensation reactions happening on sol-gel process. This photoinduced alternative is particularly adapted for preparation of thin films and has lots of advantages such as photolatent, stable, solvent and water free initial formulation along with faster reaction rates. In one hand, from simple inorganic precursors, a kinetic and mechanistic study of the photoacid-catalyzed sol-gel reactions was realized. Then, we attempt to define what chemical, physical and photochemical parameters determine the precise sequence, kinetics and advancement of these reactions under different processing conditions Furthermore, an equivalent photobase-catalyzed sol-gel process has been also studied thoroughly. In a second hand, we focus on application of this photoinduced process for the preparation of mesoporous silica films. A triblock copolymer surfactant was added to the initial inorganic precursor. Feasibility of this photochemical approach from water and solvent free formulation was first investigated and mesoporous films were obtained. Then, we work on understanding the two interdependent mechanisms: surfactant self-assembly and inorganic network condensation. The system was after that optimized in order to have a precise control of pore size and structure. Finally, the last point involves organic photodegradation in order to liberate porosity
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Morris, Jason C. „Photosensitive alkoxyamines: Synthesis and photochemical studies for potential application in nitroxide-mediated photopolymerization“. Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/110527/1/Jason_Morris_Thesis.pdf.
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Photopolymerization has increasing application in high tech domains such as microelectronics, laser direct imaging technology and 3D printing. Continued development of these technologies requires increasing control over the spatial resolution of polymer architectures, as well as the ability to tailor polymer properties to a specific application. Controlled photopolymerization methodologies, such as nitroxide-mediated photopolymerization, have demonstrated important proof of concept advances to polymer architectures and properties. In order to advance this burgeoning methodology, this thesis investigates the synthesis, as well as the photophysical and photochemical properties, of novel photosensitive alkoxyamines, for potential application in nitroxide-mediated photopolymerization.
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CAPRIOLI, MATTEO. „Development and fabrication of self-healing hydrogels via vat photopolymerization 3D printing technology“. Doctoral thesis, Politecnico di Torino, 2022. http://hdl.handle.net/11583/2971993.
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Morris, Jason. „Photosensitive alkoxyamines : synthesis and photochemical studies for potential application in nitroxide-mediated photopolymerization“. Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4746.
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Les travaux décrits dans cette thèse portent sur la synthèse ainsi que l’étude physico-chimique et photo-chimique de plusieurs séries de nitroxydes et d’alcoxyamines photosensibles fonctionnalisées par des chromophores de type benzophénone, fluorènone, anthraquinone, phényle, naphtyle et anthracényle. En particulier, nous avons focalisé notre effort sur l’introduction de ces chromophores sur un nitroxyde dérivé d’un noyau isoindoline connu pour sa stabilité photo-chimique. L’étude de la photo-dissociation des alcoxyamines préparées a ensuite été conduite par résonance paramagnétique électronique. Les résultats obtenus mettent en évidence deux nouvelles classes d’alcoxyamines photosensibles qui présentent une efficacité remarquable de photo-dissociation homolytique pour donner les radicaux nitroxyle et alkyle correspondant sous UV et irradiation de lumière visible. En effet, les alcoxyamines de type naphtyle et anthraquinone ont donné des rendements de dissociation homolytique quantitatifs sous irradiation UV et visible, et ce, quel que soit le fragment alkyle libéré (i.e. styryle, méthacrylyle, acrylyle). De plus, nous avons également montré que les nitroxydes portant les chromophores naphtyle et anthraquinone présentent une stabilité photochimique élevée. Ainsi, l’analyse de ces résultats suggère que les alcoxyamines dérivées de ces deux nitroxydes présentent toutes les caractéristiques requises pour être des candidats performants en photopolymérisation radicalaire contrôlée en présence de nitroxydesThe work reported herein details the synthesis, as well as the photophysical and photochemical analysis, of novel unsubstituted benzophenone-, methoxy substituted benzophenone-, pyrrolidine substituted benzophenone-, fluorenone-, anthraquinone-, phenyl-, naphthyl- and anthracenyl-based photosensitive alkoxyamines for potential application in nitroxide-mediated photopolymerization.The high photochemical stability of the isoindoline class of nitroxide was exploited within the structural design. Fusion of the isoindoline motif into the examined chromophores facilitated efficient energy transfer between chromophore and alkoxyamine motifs, whilst exerting minimal influence on the photophysical properties of the investigated chromophores. Photochemical investigation of the examined alkoxyamines highlighted two new classes of photosensitive alkoxyamines which displayed highly desirable photo-dissociation efficiencies to afford nitroxide and alkyl radicals under UV and visible light irradiation. Specifically, styrenic, methacrylic and acrylic naphthyl-based alkoxyamines, as well as, styrenic and methacrylic anthraquinone-based alkoxyamines demonstrated near quantitative yields of photo-dissociation under UV and visible light irradiation respectively. The high yields of photo-dissociation obtained for the naphthyl- and anthraquinone-based systems, as well as the high photochemical stability of their corresponding nitroxides, indicate these new classes of photosensitive alkoxyamines are highly relevant candidates for further investigation within a photopolymerization context
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Morris, Jason. „Photosensitive alkoxyamines : synthesis and photochemical studies for potential application in nitroxide-mediated photopolymerization“. Electronic Thesis or Diss., Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4746.
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Les travaux décrits dans cette thèse portent sur la synthèse ainsi que l’étude physico-chimique et photo-chimique de plusieurs séries de nitroxydes et d’alcoxyamines photosensibles fonctionnalisées par des chromophores de type benzophénone, fluorènone, anthraquinone, phényle, naphtyle et anthracényle. En particulier, nous avons focalisé notre effort sur l’introduction de ces chromophores sur un nitroxyde dérivé d’un noyau isoindoline connu pour sa stabilité photo-chimique. L’étude de la photo-dissociation des alcoxyamines préparées a ensuite été conduite par résonance paramagnétique électronique. Les résultats obtenus mettent en évidence deux nouvelles classes d’alcoxyamines photosensibles qui présentent une efficacité remarquable de photo-dissociation homolytique pour donner les radicaux nitroxyle et alkyle correspondant sous UV et irradiation de lumière visible. En effet, les alcoxyamines de type naphtyle et anthraquinone ont donné des rendements de dissociation homolytique quantitatifs sous irradiation UV et visible, et ce, quel que soit le fragment alkyle libéré (i.e. styryle, méthacrylyle, acrylyle). De plus, nous avons également montré que les nitroxydes portant les chromophores naphtyle et anthraquinone présentent une stabilité photochimique élevée. Ainsi, l’analyse de ces résultats suggère que les alcoxyamines dérivées de ces deux nitroxydes présentent toutes les caractéristiques requises pour être des candidats performants en photopolymérisation radicalaire contrôlée en présence de nitroxydesThe work reported herein details the synthesis, as well as the photophysical and photochemical analysis, of novel unsubstituted benzophenone-, methoxy substituted benzophenone-, pyrrolidine substituted benzophenone-, fluorenone-, anthraquinone-, phenyl-, naphthyl- and anthracenyl-based photosensitive alkoxyamines for potential application in nitroxide-mediated photopolymerization.The high photochemical stability of the isoindoline class of nitroxide was exploited within the structural design. Fusion of the isoindoline motif into the examined chromophores facilitated efficient energy transfer between chromophore and alkoxyamine motifs, whilst exerting minimal influence on the photophysical properties of the investigated chromophores. Photochemical investigation of the examined alkoxyamines highlighted two new classes of photosensitive alkoxyamines which displayed highly desirable photo-dissociation efficiencies to afford nitroxide and alkyl radicals under UV and visible light irradiation. Specifically, styrenic, methacrylic and acrylic naphthyl-based alkoxyamines, as well as, styrenic and methacrylic anthraquinone-based alkoxyamines demonstrated near quantitative yields of photo-dissociation under UV and visible light irradiation respectively. The high yields of photo-dissociation obtained for the naphthyl- and anthraquinone-based systems, as well as the high photochemical stability of their corresponding nitroxides, indicate these new classes of photosensitive alkoxyamines are highly relevant candidates for further investigation within a photopolymerization context
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Júnior, Marco Antonio Horn. „Efeito da mistura de fotoiniciadores acilfosfínicos e canforquinona na eficiência da polimerização“. Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/75/75131/tde-18042008-101221/.
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Foi estudado o processo de fotopolimerização iniciado através de misturas dos fotoiniciadores, acilfosfínicos (MAPO e BAPO), com canforquinona (CQ). Também foi investigada a existência de um possível efeito sinérgico durante a fotoiniciação. A eficiência de polimerização das duas misturas, MAPO/CQ e BAPO/CQ, foi determinada por actinometria. A fotodilatometria foi a técnica utilizada para o acompanhamento das cinéticas de polimerização. A adição do co-iniciador EDB não apresentou efeito nas velocidades de polimerização iniciadas pelos fotoiniciadores acilfosfínicos. Do ponto de vista do rendimento quântico de polimerização, um efeito antagonístico foi observado devido a transferência de energia a partir dos fotoiniciadores mais eficientes (MAPO ou BAPO) para o menos eficiente, canforquinona (CQ).The photopolymerization processes involving two different photoinitiators: acylphosphine oxides (MAPO and BAPO) and camphorquinone (CQ) were studied in order to determine possible synergistic effects. The polymerization efficiency of the two mixtures, MAPO/CQ and BAPO/CQ, was studied using actinometry. The polymerization kinetics was followed by photodilatometry. The presence of the coinitiator EDB had no effect in the polymerization rate initiated by the acylphosphine oxides. From the point of view of photopolymerization quantum yields, an antagonistic effect is observed due to the energy transfer from the more efficient initiator (MAPO or BAPO) to the less efficient (CQ).
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Koch, Horst, André Laschewsky, Helmut Ringsdorf und Kang Teng. „Photodimerization and photopolymerization of amphiphilic cinnamic acid derivatives in oriented monolayers, vesicles and solution“. Universität Potsdam, 1986. http://opus.kobv.de/ubp/volltexte/2008/1711/.
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Cinnamic acid moieties were incorporated into amphiphilic compounds containing one and two alkyl chains. These lipid-like compounds with photoreactive units undergo self-organization to form monolayers at the gas-water interface and bilayer structures (vesicles) in aqueous solutions. The photoreaction of the cinnamic acid moiety induced by 254 nm UV light was investigated in the crystalline state, in monolayers, in vesicles and in solution in organic solvents. The single-chain amphiphiles undergo dimerization to yield photoproducts with twice the molecular weight of the corresponding monomers in organized systems. The photoreaction of amphiphiles containing two cinnamic acid groups occurs via two mechanisms: The intramolecular dimerization produces bicycles, with retention of the molecular weight of the corresponding monomer. The intermolecular reaction leads to oligomeric and polymeric photoproducts. In contrast to the single-chain amphiphiles, photodimerization processes of lipoids containing two cinnamic acid moieties also occur in solution in organic solvents.
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Rahane, Santosh Bhagwat. „Kinetics of surface-initiated photoiniferter-mediated photopolymerization and synthesis of stimuli-responsive polymer brushes“. Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1181668711/.
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Chartrain, Nicholas. „Designing Scaffolds for Directed Cell Response in Tissue Engineering Scaffolds Fabricated by Vat Photopolymerization“. Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/95939.
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Vat photopolymerization (VP) is an additive manufacturing (AM) technology that permits the fabrication of parts with complex geometries and feature sizes as small as a few microns. These attributes make VP an attractive option for the fabrication of scaffolds for tissue engineering. However, there are few printable materials with low cytotoxicity that encourage cellular adhesion. In addition, these resins are not readily available and must be synthesized. A novel resin based on 2-acrylamido-2-methyl-1-propanesulfonic acid (NaAMPS) and poly(ethylene glycol) diacrylate (PEGDA) was formulated and printed using VP. The mechanical properties, water content, and high fidelity of the scaffold indicated promise for use in tissue engineering applications. Murine fibroblasts were observed to successfully adhere and proliferate on the scaffolds.
The growth, migration, and differentiation of a cell is known to dependent heavily on its microenvironment. In engineered constructs, much of this microenvironment is provided by the tissue scaffold. The physical environment results from the scaffold's geometrical features, including pore shape and size, porosity, and overall dimensions. Each of these parameters are known to affect cell viability and proliferation, but due to the difficulty of isolating each parameter when using scaffold fabrication techniques such as porogen leaching and gas foaming, conflicting results have been reported. Scaffolds with pore sizes ranging from 200 to 600 μm were fabricated and seeded with murine fibroblasts. Other geometric parameters (e.g., pore shape) remained consistent between scaffold designs. Inhomogeneous cell distributions and fewer total cells were observed in scaffolds with smaller pore sizes (200-400 μm). Scaffolds with larger pores had higher cell densities that were homogeneously distributed. These data suggest that tissue scaffolds intended to promote fibroblast proliferation should be designed to have pore at least 500 μm in diameter.
Techniques developed for selective placement of dissimilar materials within a single VP scaffold enabled spatial control over cellular adhesion and proliferation. The multi-material scaffolds were fabricated using an unmodified and commercially available VP system. The material preferences of murine fibroblasts which resulted in their inhomogeneous distribution within multi-material scaffolds were confirmed with multiple resins and geometries. These results suggest that multi-material tissue scaffolds fabricated with VP could enable multiscale organization of cells and material into engineered constructs that would mimic the function of native tissue.Doctor of Philosophy
Vat photopolymerization (VP) is a 3D printing (or additive manufacturing) technology that is capable of fabricating parts with complex geometries with very high resolution. These features make VP an attractive option for the fabrication of scaffolds that have applications in tissue engineering. However, there are few printable materials that are biocompatible and allow cells attachment. In addition, those that have been reported cannot be obtained commercially and their synthesis requires substantial resources and expertise. A novel resin composition formulated from commercially available components was developed, characterized, and printed. Scaffolds were printed with high fidelity. The scaffolds had mechanical properties and water contents that suggested they might be suitable for use in tissue engineering. Fibroblast cells were seeded on the scaffolds and successfully adhered and proliferated on the scaffolds. The growth, migration, and differentiation of cells is influenced by the environmental stimuli they experience. In engineered constructs, the scaffold provides many of stimuli. The geometrical features of scaffolds, including how porous they are, the size and shape of their pores, and their overall size are known to affect cell growth. However, scaffolds that have a variety of pore sizes but identical pore shapes, porosities, and other geometric parameters cannot be fabricated with techniques such as porogen leaching and gas foaming. This has resulted in conflicting reports of optimal pore sizes. In this work, several scaffolds with identical pore shapes and porosities but pore sizes ranging from 200 μm to 600 μm were designed and printed using VP. After seeding with cells, scaffolds with large pores (500-600 μm) had a large number of evenly distributed cells while smaller pores resulted in fewer cells that were unevenly distributed. These results suggest that larger pore sizes are most beneficial for culturing fibroblasts. Multi-material tissue scaffolds were fabricated with VP by selectively photocuring two materials into a single part. The scaffolds, which were printed on an unmodified and commercially available VP system, were seeded with cells. The cells were observed to have attached and grown in much larger numbers in certain regions of the scaffolds which corresponded to regions built from a particular resin. By selectively patterning more than one material in the scaffold, cells could be directed towards certain regions and away from others. The ability to control the location of cells suggests that these printing techniques could be used to organize cells and materials in complex ways reminiscent of native tissue. The organization of these cells might then allow the engineered construct to mimic the function of a native tissue.
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Kim, Namil. „Photoisomerization - And Photopolymerization-Induced Phase Transitions in Mixtures of Photoresponsive Chromophores and Reactive Mesogens“. University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1280254227.
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Dillman, Brian F. „The kinetics and physical properties of epoxides, acrylates, and hybrid epoxy-acrylate photopolymerization systems“. Diss., University of Iowa, 2013. https://ir.uiowa.edu/etd/2476.
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Photopolymerization, which uses light rather than heat to initiate polymerization, is a facile technique used to fabricate adhesives, protective coatings, thin films, photo-resists, dental restoratives, and other materials. Epoxide monomers, which are polymerized via cationic photoinitiation, have received less attention in fundamental research in comparison to free radical polymerized acrylate monomers. The characterization of propagation mechanisms, network structures, and physical properties is yet lacking.
This project focused on the reactivity and physical properties of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate (EEC), and the kinetic and physical effects of chain transfer agents (CTAs) in EEC based formulations were characterized. This characterization was carried out using real-time Raman spectroscopy, real-time infrared spectroscopy, dynamic mechanical analysis, simple gel fraction measurements, and atomic force microscopy. The effects of water, organic alcohols, processing conditions (e.g., UV light intensity, humidity, post-illumination curing temperature), and photoinitiation systems were investigated.
In general, increasing the concentration of CTAs in a crosslinking epoxide resin increases the rate of polymerization and the overall epoxide conversion level. High CTA levels also correspond to lower glass transition temperatures (Tg) and lower crosslink densities. A post-illumination annealing was critical in obtaining stable physical properties for high Tg epoxide materials. In addition, humidity (water being the most universal contaminant type of CTA) was found to impact the surface properties of an epoxide polymer negatively by reducing the surface hardness.
Hybrid acrylate-epoxide systems are much more complex and unpredictable in curing behavior. The use of hydroxy acrylates in hybrid systems allows for grafting between the epoxide and the acrylate domains, via the AM mechanism. Another intricacy of hybrid systems is the initiation system. In order to maximize the conversion of both the epoxide and the acrylate moieties, the free-radical photoinitiator must not hinder the polymerization of the epoxide monomer. Some very efficient free-radical photoinitiators limit the epoxide polymerization by absorbing the majority of the deep-UV incident photons.
Finally, a renewable acrylate oligomer was synthesized to provide a green alternative to petroleum-based oligomers currently used. The oligomer was freely miscible and readily photopolymerized with a wide range of commercial monomers. The Tg relationship between the commercial monomers and the parent resin followed the Fox equation.
The results of this research provide strategies for controlling epoxide kinetics and physical properties in neat and hybrid systems. This information is useful for tailoring resin formulations to specific end-use applications, especially in films, coatings, and adhesives.
Hybrid epoxide-acrylate photopolymerization affords the unique opportunity to structure polymer networks in time and to engineer advanced material properties. These hybrid systems are based on formulations that contain both an epoxide moiety, which undergoes cationic ring-opening photopolymerization, and an acrylate moiety, which undergoes free-radical photopolymerization. Through the combination of these two independent reactive systems, hybrid polymers exhibit lower sensitivity to oxygen and moisture and offer advantages such as increased cure speed and improved film-forming properties. The ability to design the polymer network architecture and to tune mechanical properties can be realized through control of the cationic active center propagation reaction relative to the cationic chain transfer reaction. Specifically, grafted polymer networks can be developed through the covalent bonding of the epoxide chains to the acrylate chains via hydroxyl substituents. This work demonstrates the formation of these grafted polymer networks and overviews the physical properties obtained through control of hydroxyl content and hybrid formulation composition.
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Chen, Hongshi. „Contribution to Active Probe for SNOM and Nanoscale Light-matter Interaction based on Photopolymerization“. Electronic Thesis or Diss., Troyes, 2022. http://www.theses.fr/2022TROY0007.
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La microscopie optique en champ proche à balayage (SNOM) est une technologie d'imagerie optique à haute résolution. L'information associée aux hautes fréquences spatiales du champ proche est associée à une haute résolution spatiale, permettant de dépasser la limite de diffraction. Développer une sonde optique locale efficace reste un sujet clé d'actualité qui est abordé depuis longtemps. La thèse porte sur le développement d'une sonde en champ proche active basée sur une pointe polymère intégrée à l'extrémité d'une fibre optique. Nous avons polymérisé une pointe en polymère sur la surface de l'extrémité de la fibre. Pour le balayage, les forces locales de cisaillement détectées à l’aide d’un micro diapason sur lequel est collée la sonde sont utilisées pour contrôler la distance sonde-échantillon. Après fonctionnalisation de surface de la sonde polymère, quelques nano-émetteurs ont été attachés sur l'extrémité de la sonde, pour obtenir une sonde active. Les nano-émetteurs peuvent servir de source lumineuse locale pour la sonde active. La stratégie d’intégration de nano-emetteurs développée a été utilisée sur des nanocubes d'or sur substrat, pour concevoir des nano-émetteurs de plasmons hybrides sensibles à la polarisation. Nous avons également étendu ces nano-émetteurs hybrides au régime de photon unique. Enfin, la sonde active a été testée sur deux types d'échantillons : des nanofils d'argent et des nanocubes d'or. En utilisant notre nouvelle sonde active, nous avons collecté des informations de champ proche pour ces nanostructures et dépassé la limite de diffractionScanning Near-field Optical Microscope (SNOM) is a technology for high resolution optical imaging. The high spatial frequency information from the near-field is associated to high spatial resolution, allowing one to break the diffraction limit. The used local probe is still a key topical issue that has been addressed for long. The thesis deals with the development of an active near-field probe based on a polymer tip integrated at the extremity of an optical fiber. We polymerized polymer tip on the surface of the fiber end as a scanning optical probe. Shear-force method with micro tuning fork is used for controlling the probe-sample distance. After surface functionalization of the polymer probe, a few nano-emitters have been attached on the probe extremity, to obtain an active probe. Upon excitation, the nano-emitters can act as local light source for the active probe. Besides, while the development of such active hybrid probes turned out to be challenging, the developed strategy of attachment has been used on gold nanocubes on substrate, to create polarization-sensitive hybrid plasmon nano-emitters. We also extended this hybrid nano-emitters to single photon regime. Finally, the active probe was tested on two kinds of samples: silver nanowires and gold nanocubes. By using our new active probe, we obtained near-field information for those nanostructures and broke the diffraction limit
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Zuo, Xiaoling. „Fluorescent Brighteners in Polymerizations under Visible-light LED : Toward Versatile and High Performance Photoinitiating Systems“. Thesis, Mulhouse, 2017. http://www.theses.fr/2017MULH0738/document.
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Le développement d'un nouveau système photo-initiateur 1 photoinitiateur capable d'absorber fortement la lumière dans la région de la lumière visible et de travailler sous irradiation LED a fait des progrès gratifiants. Ici, notamment l'azurant fluorescent en tant que classe de dérivés fluorophores, a été confirmé comme un Pl efficace pour la photopolymérisation radicalaire (FRP), l'un des principaux avantages est qu'ils peuvent travailler efficacement sous l'air, même à faible intensité lumineuse. Lorsqu'ils sont incorporés dans des systèmes photoinitiateurs multicomposants (en présence de sel d'iodonium (et éventuellement N-vinylcarbazole ou amine)), les dérivés du naphtalène-benzoxazole, des triazinylstilbènes sulfonés, du stilbène-biphényl sulfoné et du coumarinme inhibent d'excellentes capacités photoamorcantes pour la FRP des acrylates sous air. De plus, ils sont particulièrement efficaces pour la formation d'un réseau de polymères interpénétrés à travers une photopolymérisation cationique 1 radicale concomitante d'un mélange époxydes 1 acrylates.De plus, la substitution d'une certaine teneur en monomère acrylate avec de l'eau augmente positivement la conversion finale des fonctions acrylate polymérisables, spécialement formulée avec les systèmes initiateurs à base d'azurants hydrophiles. En outre, une formulation aqueuse d'acrylate contenant des systèmes d'amorçage à base d'azurants a permis la synthèse d'hydrogels assistée par LED. Cette méthode de synthèse consomme moins d'énergie et les hydrogels produits ont généralement une teneur élevée en eau. Et, l'étude des photopolymérisations qui se déroulent dans les mélanges acrylate 1 eau élargit les perspectives pour le polymère vert et la chimie organiqueThe development of a new photoinitiator/photoinitiatng system being capable of strongly absorbing light in the visible-light region and working under LED irradiation has made gratifying advance. Herein, notably the fluorescent brightener as one class of fluorophore derivetives, has been confirmed as an efficient Pl for free radical photopolymerization (FRP), one of the major advantages is thalthey could efficiently work under air even exposure to a low LED light intensity. When incorporated into multicomponent photoinitiating systems (in the presence of iodonium salt (and optionally N-vinyl carbazole or amine)), the derivatives of naphthalene benzoxazole, sulfonated triazinylstilbenes, sulfonated stilbene-biphenyl and coumarinmexhibit quite excellent photoinitiating abilities for FRP of acrylates under air. Moreover, they are particularly efficient for the formation of interpenetrated polymer network through a concomitant cationic/radical photopolymerization of epoxides/acrylates blend.Additionally, substitution of a certain content of acrylate monomer with water is found to positively increase the final conversion of polymerizable acrylate functions, especially formulated with the hydrophilic brighteners-based initiating systems. Besides, an aqueous acrylate formulation containing brighteners-based initiating systems enabled the LED-assisted synthesis of hydrogels. This synthetic method is less energy-intensive and the hydrogels produced are typically of high water content. And, the investigation of photopolymerizations thal proceed in acrvlate/water blends broadens the perspectives for qreen polvmer and organic chemistry
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Aloui, Faten. „Photopolymérisation de formulations composites : étude de l’évolution des propriétés optiques“. Thesis, Rouen, INSA, 2015. http://www.theses.fr/2015ISAM0001/document.
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L’objectif est d’étudier les propriétés optiques de formulations composites et leur évolution durant leur photopolymérisation. Une attention particulière est portée au phénomène de diffusion de la lumière engendré par la présence de charges d’indice de réfraction différent de celui de la matrice organique. Des relations indice-conversion sont établies pour des systèmes non chargés à partir des suivis cinétiques de l’évolution de l’indice de réfraction par réfractométrie et de la conversion par spectrométrie IR réalisés pour différentes compositions, température et intensité du rayonnement. L’étude des formulations chargées montre que la diffusion de la lumière est d’autant moins marquée que l’écart d’indice de réfraction entre charges et matrice est faible et la taille des particules est grande. Une modélisation basée sur un modèle à 4 flux décrivant l’évolution du rayonnement dans l’épaisseur de l’échantillon permet d’optimiser le mode opératoire le plus adapté au matériau viséThe aim of this work is to study optical properties of loaded formulations and their variation during photopolymerization. This study is accentuated on light scattering phenomenon which is caused by presence of fillers having refractive index different from that of the organic matrix. Using real time monitoring of photopolymerization kinetics by IR spectroscopy and by refractometry, refractive index-conversion relationships are determined for unloaded systems of different compositions and at different temperatures and radiation intensities. Studying loaded formulations shows that light scattering is even less so pronounced as the difference in refractive index between fillers and matrix is lower and as the particle size is larger. Modeling based on four-flux theory was used to describe radiation evolution in terms of sample thickness in order to optimize the most appropriate operating procedure of the desired material
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Voltarelli, Fernanda Regina. „Avaliação do efeito da indução de polimerização com diferentes fontes de luz e dos meios de envelhecimento sobre a microdureza de cilindros de resina composta“. [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/289118.
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Orientador: Giselle Maria Marchi BaronDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
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Resumo: O objetivo deste estudo foi avaliar o efeito do tipo de fonte de luz (Halógena/HAL, Diodos Emissores de Luz/LED, Laser de Argônio/LAS e Arco de Plasma/PAC) e dos meios de envelhecimento sobre a microdureza das superfícies de topo e base de cilindros de resina composta com 4mm de altura. Para este estudo foram confeccionados 200 corpos de prova em resina composta Filtek Z250 (3M ESPE) a partir de matrizes metálicas bipartidas cilíndricas (5mm de diâmetro e 4mm de altura), divididos, aleatoriamente, em 20 grupos (n=10) de acordo com a fonte de luz e o envelhecimento empregado (Ciclagem Mecânica/CM, Ciclagem Térmica/CT, Estocagem/E, CM+CT e CM+CT+E), onde a ciclagem térmica consistiu em 1000 ciclos, com banhos de 60s a temperaturas variando entre 5 ± 2 °C e 55 ± 2°C; a ciclagem mecânica, em 200000 ciclos com 2Hz de freqüência e carga vertical de 75N e, a estocagem, em armazenamento em solução tamponada de Hank pelo período de 1 ano. O teste de microdureza Knoop (25g; 20s) foi realizado nas superfícies de base e topo de cada corpo de prova antes e após os envelhecimentos. A análise estatística (ANOVA One-way; ANOVA em esquema de parcelas subdividades; Tukey, ?=5%; Teste para dados pareados) observou interação significativa entre os aparelhos, entre os aparelhos e os envelhecimentos e entre os tempos avaliados. Tanto para base como para o topo, antes dos envelhecimentos, PAC obteve menores valores de microdureza Knoop quando comparado à HAL. Na superfície de topo, depois dos procedimentos de envelhecimento, PAC e LAS também apresentaram valores de microdureza inferiores quando comparados à HAL. Os menores valores de dureza, dentre os procedimentos de envelhecimentos testados, foram obtidos pelos corpos de prova submetidos à estocagem (CM+CT+E e E). Na superfície de base, para PAC não houve diferença entre os envelhecimentos, enquanto para HAL, LED e LAS, CM+CT+E e E obtiveram menores valores de microdureza Knoop. Quando procedimentos de CM, CT e CM+CT foram realizados, PAC obteve valores de dureza inferiores, enquanto para CM+CT+E e E não houve diferença entre as fontes de luz utilizadas. Assim, podemos concluir que a qualidade do polímero formado pelo PAC pode ter reduzido os valores de microdureza knoop obtidos tanto na base como no topo antes dos envelhecimentos e no topo, juntamente com o LAS, depois dos envelhecimentos. Dessa forma, podemos notar que HAL ainda demonstra adequada polimerização das resinas compostas. Além disso, podemos concluir que todos os procedimentos de envelhecimento influenciaram adversamente as amostras confeccionadas com PAC, e que os procedimentos de estocagem (CM+CT+E e E) foram os procedimentos de envelhecimento que mais afetaram os valores de microdureza Knoop, apresentando-se prejudiciais para todas as fontes de luz
Abstract: The aim of this study was to evaluate the effect of the light-curing devices (Halogen/HAL, Light Emitting Diodes/LED, Argon Laser/LAS and Plasma Arc/PAC) and aging procedures on the microhardness of bottom and top surfaces of resin composite cylinders with 4mm height, submitted to thermal and mechanical cycles, and one year storage. For this study 200 specimens of Filtek Z250 (3M ESPE) were prepared from metallic molds, and randomly allocated in 20 groups (n=10) according to the light source and the aging procedure employed (Mechanical Cycling/CM, Thermal Cycling/CT, Storage/E, CM+CT and CM+CT+E). The thermal cycling consisted of 1000 cycles (5±2C/55±2C)oo, the mechanical cycling in 200000 cycles (75N/2Hz), and the storage procedure in one year of storage in Hank solution. The microhardness test on bottom and top surfaces (25g/20s) was performed before and after the aging process. The statistical analysis (repeated measures of variance analysis and non parametric test) showed significant interaction between the devices, between the devices and the aging process, and also between the evaluated times. For base and top surfaces, before the aging procedures, PAC demonstrated reduced polymerization effectiveness when compared to HAL. In the top surface, after the aging procedures, PAC and LAS had also presented reduced polymerization effectiveness when compared to HAL. The lower hardness values, among the aging procedures tested, had been showed by the specimens submitted to storage (CM+CT+E and E). In the base surface, PAC did not presented differences between the aging procedures, while for HAL, LED and LAS, CM+CT+E and E had reduced the microhardness values. When CM, CT and CM+CT had been performed, PAC showed reduced polymerization effectiveness, while for CM+CT+E and E there was no difference between the light sources. Thus, we can conclude that the quality of the polymer formed by PAC reduced the microhardness values on the base and top surfaces before the aging process, and in the top surface after the aging procedures. It should be noted that HAL still demonstrate an adequate polymerization of resin composite. Moreover, we can conclude that all the aging procedures had been harmful for the samples confectioned with PAC, and that the storage procedures (CM+CT+E e E) were the aging procedures that had affected more the Knoop microhardness values, presenting themselves as harmful for all the light sources
Mestrado
Dentística
Mestre em Clínica Odontológica
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Ferreira, Giovana Chimello. „\"Fotopolimerização iniciada por tioxantona e outros indicadores - Estudos fundamentais e aplicações\"“. Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/75/75131/tde-29012007-112944/.
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A cinética de fotopolimerização do monômero metacrilato de metila (MMA) foi investigada usando o fotoiniciador tioxantona (TX) e o co-iniciador trietilamina (TEA), a fim de elucidar o mecanismo de fotopolimerização. A dilatometria foi usada como técnica para a determinação das cinéticas de polimerização. Determinaram-se os rendimentos quânticos de polimerização. Os estados excitados foram estudados por fluorescência estática para determinar as constantes de supressão de fluorescência pela amina e pelo monômero. Medidas de fotólise por pulso de laser permitiram obter o espectro de absorção triplete-triplete da tioxantona, bem como a constante de supressão do estado triplete. Os resultados mostraram que a supressão ocorre por um processo colisional no estado singlete e que os radicais eficientes na fotoiniciação são originados da amina TEA. A massa molecular média dos polímeros obtidos foi determinada por medidas de cromatografia de permeação em gel (GPC). Em uma segunda etapa, foi investigada a polimerização fotoiniciada por fotoiniciadores usados em resinas dentárias, canforquinona (CQ), 1,2-fenilpropanodiona (PPD), Lucirin e Irgacure. A velocidade de polimerização foi acompanhada por dilatometria usando excitação acima de 348 nm. Obteve-se os rendimentos quânticos de polimerização e os polímeros foram caracterizados por GPC. A maior constante de velocidade de polimerização obtida foi para o Irgacure e o maior rendimento quântico de polimerização obtido foi para o Lucirin. As diferenças na eficiência da polimerização são atribuídas à formação de radicais e à capacidade de gerar radicais a partir da absorção da luz incidente. Por fim, investigou-se os espectros de absorção triplete-triplete (TTA) da TX em diferentes solventes usando a técnica de fotólise por pulso de laser. Observou-se a formação de três bandas, duas referentes ao triplete da TX (uma em 300 nm e outra em 600 nm) e em 400 nm, observou-se a formação do radical cetila da TX. A abstração de hidrogênio do solvente pela TX pode ocorrer em 340 nm em solventes com constante de abstração de hidrogênio (kabstr) alto. Esse fator pode ser observado nos solventes 2-propanol e etanol. O substituinte na TX mostrou, através do parâmetro de Hammett do substituinte que com o aumento da eletronegatividade há um deslocamento do máximo de absorção do transiente para comprimentos de onda menores.The photopolymerization of the monomer methyl methacrylate (MMA) using thioxanthone (TX) as photoinitiator and triethylamine (TEA) as co-initiator, was investigated in order to explain the photopolymerization mechanism. Dilatometry was used to determine the kinetics of polymerization. The polymerization quantum yields were determined. The excited states were studied using static fluorescence in order to determine the fluorescence rate quenching by the amine and the monomer. The triplet-triplet absorption (TTA) spectrum of thioxanthone and the rate constant of quenching of the triplet state were obtained using flash photolysis technique. The results showed that the singlet state quenching occurs by a colisional process and the efficient radicals in the photoinitiation process are originated from the amine TEA. The molar mass of the obtained polymers was determined by gel permeation chromatography (GPC). The polymerization photoinitiated by the photoinitiators used in dental resins, Camphorquinone (CQ), 1,2- Phenylpropanodione (PPD), Lucirine and Irgacure was investigated in a second step. The rate of polymerization was studied by dilatometry with excitation above 348 nm. The polymerization quantum yields were obtained and the polymers were characterized by GPC. The larger rate constant of polymerization was found for Irgacure and the larger polymerization quantum yield was obtained for Lucirine. The differences in polymerization efficiencies can be tracked to the formation of radicals and the capability to produce the radicals after incident light absorption. Finally, the TTA of TX was studied in different solvents using the flash photolysis technique. The spectrum presented three bands, two due to the transient of TX (at 300 and 600 nm), and one at 400 nm assigned to the cetyl radical. The abstraction of a solvent hydrogen by TX is observed at 340 nm in solvents with high hydrogen abstraction constant (kabstr). This fact can be observed in 2-propanol and ethanol. An increase in the solvent polarity stabilizes the electronic pp* states and unstabilizes the np* states. The substitution in the TX molecule produced a shift to lower wavelength in the maximum absorption of transient with the increase of the electronegativity, as indicated by the dependence of the Hammett parameter.
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Nunes, Margareth Calvo Pessutti. „Avaliação da microdureza e desgaste por escovação simulada de uma resina composta, em função de diferentes fontes de luz e energias de ativação“. Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/25/25131/tde-20062007-105425/.
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Este estudo in vitro teve como objetivo avaliar comparativamente a microdureza superficial e o desgaste de uma resina composta, FiltekTM Z-250 (3M/ESPE), sob influência de diferentes fontes de luz (LED Ultrablue IS - DMC, LED Ultralume 5 - Ultradent e halógena VIP - BISCO), com variação das densidades de potência (300, 600 e acima de 800mW/cm2) e energia (6, >8, 12, >16, 24, >32 J/cm2). Espécimes retangulares (15 x 5 x 4 mm) foram polimerizados, conforme os fatores de variação, totalizando 15 grupos (n=6). Em seguida receberam acabamento e polimento com lixas de abrasividade decrescente (300, 600, 1200 e 2000), sendo armazenados em água deionizada a 37º C por sete dias. As mensurações da microdureza Knoop foram realizadas com auxílio do Microdurômetro Shimadzu HMV-2, com carga estática de 100g por 5s nas superfícies de topo e lateral (50µm da superfície). Posteriormente os espécimes foram levados à máquina de ensaios para simulação de desgaste por escovação, utilizando-se escovas dentais macias (Oral B 30 Indicator) e creme dental (Colgate) diluído em água deionizada na proporção de 1:2 em peso. Ao final de 100.000 ciclos, a dureza da superfície lateral foi novamente mensurada e o desgaste da área escovada foi determinado por meio de perfilometria (Hommel Tester T 1000 basic - Hommelwerke). Os dados de microdureza e desgaste superficial obtidos foram submetidos à análise de variância (ANOVA) e teste de Tukey (p<0,05). Os resultados evidenciaram que a microdureza superficial da resina composta avaliada foi significantemente menor quando da fotoativação com VIP-300 mW/cm2, sendo que os maiores valores foram observados com o aparelho Ultralume 5. O desgaste superficial foi significativamente influenciado quando da utilização de baixa densidade de potência (300 mW/cm2) e energia de 6 J/cm2, tanto com o VIP como Ultrablue IS, que demonstraram maior efetividade quando da utilização de densidade de energia acima de 12J/cm2. De forma geral, observou-se correlação negativa quando da interação dos testes de dureza e desgaste superficial, ou seja, quando os valores de dureza aumentaram os de desgaste diminuíram inferindo, entretanto, que isoladamente o valor de dureza não constitui em parâmetro para qualificar o desempenho da resina composta quanto à resistência ao desgaste.This in vitro study evaluated comparatively, the superficial microhardness and wear of a resin composite, FiltekTM Z-250 (3M/ESPE) under the influence of different light sources (LED Ultrablue IS/DMC, LED Ultralume 5/Ultradent and halogen VIP/BISCO); with power (300, 600 and above 800mW/cm2) and energy density (6, >8, 12, >16, 24, >32J/cm2) variations. Rectangular specimens (15 x 5 x 4 mm) were polymerized, as the variation factors, totalizing 15 groups (n=6). After, they were ground flat with water-cooled carborundum discs in decreasing abrasive order (300, 600, 1200 and 2000) and stored for seven days, before the tests, in deionized water at 37º C. The Knoop microhardness measurements were carried out using a microhardness tester (Shimadzu HMV-2), with a 100g static load applied for 5s on specimens\' top and lateral surfaces (50µm under surface). In sequence the specimens were taken to a machine for brushing simulation, using soft nylon bristles (Oral B 30 Indicator) and dental paste (Colgate) diluted in deionized water in the ratio of 1:2 in weight. After 100,000 cycles, the hardness of the lateral surface was again measured and the wear profile of the brushed area was determined by a profilometer (Hommel Tester T 100 basic/Hommelwerke). The microhardness and superficial wear data were submitted to the analysis of variance (ANOVA) and Tukey test (p<0.05). The results showed that the superficial microhardness of the evaluated resin composite was significantly lower when photoactivated with VIP-300 mW/cm2, being the biggest values observed for the Ultralume 5 device. The superficial wear was significantly influenced by the low power density (300 mWcm2) and energy density of 6 J/cm2. This was for both, VIP and Ultrablue IS, which demonstrated greater effectiveness when a density of energy above 12J/cm2 was used. In general, a negative correlation was observed between the two tests (wear and microhardness). In other words, there was an increase of hardness with the decrease in wear values, which demonstrates that only microhardness values do not constitute a parameter to qualify resin composite wear resistance behavior.
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Heimer, Brandon Walter. „Methylated DNA detection using a high-affinity methyl-CpG binding protein and photopolymerization-based amplification“. Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98796.
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Thesis: Sc. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 123-132).
Methylation at the 5 position of the cytosine base, when followed by guanine (CpG) in the promoter region of a protein-coding gene, is an epigenetic modification that has been shown to be involved in gene silencing. While important for regulating many normal, cellular processes, aberrant DNA methylation has been implicated in the development of human diseases such as cancer. Medical research has begun to identify hypermethylated gene promoters that can be used as predictive, prognostic, and diagnostic biomarkers. Current technologies for DNA methylation detection, however, rely on sodium bisulfite conversion of unmethylated cytosine bases to urasil in the target DNA. Bisulfite treatment is time consuming to perform, degrades >90% of the DNA, and is susceptible to incomplete conversion which can lead to false results. As such, a method that eliminates both chemical conversion and PCR amplification of DNA would enable significantly lower-cost and rapid DNA methylation analysis in the clinic. Methyl binding domain (MBD) family proteins specifically bind double-stranded, methylated DNA which makes them excellent transducers for DNA methylation in biosensing applications. I displayed three of the core members MBD1, MBD2, and MBD4 on the surface of Saccharomyces cerevisiae yeast cells. Using the yeast display platform, I determined the equilibrium dissociation constant of human MBD2 (hMBD2) to be 5.9+/-1.3 nM for binding to singly methylated DNA. I further used the yeast display platform to evolve the hMBD2 protein for improved binding affinity. Affecting five amino acid substitutions doubled the affinity of the wildtype protein to 3.1+/-1.0 nM. Further, concatenating the high-affinity MBD variant from 1x to 3x and expressing it in Escherichia coli as a green fluorescent protein (GFP) fusion improved affinity 6-fold for interfacial binding. After optimizing the expression and purification of engineered MBD-GFP proteins in E. coli, I developed a simple method for detecting methylated DNA fragments from the MGMT gene promoter. A defining feature is that target oligonucleotides from the test sample hybridize directly to capture probes printed in 300 pm diameter spots on an inexpensive biochip without requiring bisulfite conversion. Sub-nanomolar concentrations (0.3 nM) of methylated DNA duplexes are detected using an MBD-GFP protein to transduce binding to either a fluorescent or colorimetric (visible hydrogel) signal formed by photopolymerization with short (<2 min) reaction times.
by Brandon Walter Heimer.
Sc. D.
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De, Ambroggi Elena Magdalena Verfasser], und Achim [Akademischer Betreuer] [Wixforth. „Acoustic monitoring of photopolymerization in UV curable coatings / Elena Magdalena De Ambroggi. Betreuer: Achim Wixforth“. Augsburg : Universität Augsburg, 2012. http://d-nb.info/1077700806/34.
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Jean, Chuen-Sheng, und 簡春生. „Photopolymerization of the dicoumarins“. Thesis, 1995. http://ndltd.ncl.edu.tw/handle/86969689702311183464.
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碩士國立成功大學
化學工程研究所
83
Eight dicoumarins (3,4) were successfully synthesized from 7-hydroxycoumarin (or 7-hydroxy-4-methylcoumarin) and various dibromoalkanes. Photopolymerization of the dicoumarins under 350nm light gives various corresponding polyethers 5,6. The structures of the coumarin dimer component depend on the length of flexible methylene chain, substituted groups on double bonds, polarity of solvent, and sensitizer used. The structures were characterized by NMR spectra. Dicoumarins (3) without 4-methyl substituent photopolymerize to give head-to-head products in dichloromethane. However, dicoumarins (4) with methyl substituent give head-to-tail products. Photopolymerization kinetics of 3c was also investigated. The reaction obey zeroth- order and first-order kinetics for dicoumarin and benzophenone, respectively. Finally, the polymers were photocleavaged symmetrically by 254nm UV light and then repolymerized by 350nm UV light in order to study their reversible properties.