Les problématiques et potentialités de la photopolymérisation radicalaire en miniémulsion ont été discutées, en partant de l’étude des propriétés optiques des miniémulsions de monomère jusqu’à la synthèse de nouvelles nanoparticules polysulfures semi-cristallines par réaction thiol-ène. En premier lieu, l'interaction entre les propriétés optiques de miniémulsion de monomère et l'efficacité de photopolymérisation a été clarifiée. Nous avons établi le rôle majeur de la diffusion optique sur les cinétiques de photopolymérisation de nanogouttelettes acrylates, tandis que l'absorption s’est révélé de moindre importance. Que ce soit en milieu dilué ou concentré (modèle de Kubelka-Munk), la diffusion de la lumière est atténuée lorsque la taille de gouttelettes diminue. La conséquence immédiate est une amélioration significative de la pénétration de la lumière induisant une accélération des cinétiques de polymérisation. Néanmoins, cette conclusion doit être pondérée car l’effet de compartimentage de la polymérisation radicalaire n’a pu être dissocié des effets optiques. On notera qu’en milieu concentré (contenu en solide de 30 % massique), au-delà de 150 nm pour le diamètre de gouttelette, le coefficient de diffusion atteint un palier et devient indépendant de la taille des gouttelettes. La chute d’absorbance, observée par spectroscopie UV-visible, tout au long de l’irradiation pour des miniémulsions acrylates de faible taille (40 nm) a mis en évidence un mécanisme de polymérisation par diffusion de monomère des gouttelettes non nucléées vers les particules en croissance. Cette analyse non invasive (aucune dilution n’a été nécessaire) présente un intérêt évident pour l’étude du mécanisme de nucléation. Nous avons ensuite démontré que la photopolymérisation pouvait être réalisée en utilisant le caractère auto-amorçant des acrylates sous irradiation UV court ( < 300 nm). Ce type d’amorçage photochimique a permis d’éviter l’emploi de photoamorceur, limitant ainsi les risques liés à leur présence résiduelle dans le matériau final. Les photopolymérisations ont été réalisées dans un microréacteur modèle (cuve spectroscopique d’épaisseur 0,1 à 1 mm). La variation de plusieurs paramètres expérimentaux a permis d’identifier un ensemble de paramètres clés influençant les cinétiques de polymérisation tels que la taille des gouttelettes, corroborant ainsi les résultats de l’étude optique. Les longueurs d’onde d’irradiation et le chemin optique ont joué un rôle tout aussi déterminant ; le décalage vers des longueurs d’onde courtes et la diminution de l’épaisseur de l’échantillon accélèrent à la fois la création de radicaux amorceurs et le nombre d’entités nucléées. La versatilité du procédé a été démontrée en polymérisant rapidement (conversion totale en moins de 20 min) une large gamme de monomères acrylate, méthacrylate ou à base d’acétate de vinyle. En ce qui concerne le mécanisme d’auto-amorçage, nous avons prouvé que les espèces amorçantes provenaient vraisemblablement d’un biradical photoinduit, pouvant arracher ou transférer un hydrogène sur des molécules de monomère pour former des monoradicaux amorceurs. Par le biais de ce mécanisme original, la génération de radicaux est constante tout au long de la polymérisation ce qui pour effet d’impacter les caractéristiques des copolymères formés : l’indice de polymolécularité tend à augmenter et les masses molaires à diminuer par rapport à un processus photoamorcé conventionnel. Ces photopolymérisations ont été réalisées dans un photoréacteur annulaire à immersion et ont montré les mêmes évolutions en fonction de la taille de gouttelettes que lors d’expériences en cuve spectroscopique non agitées. A titre d’exemple, une conversion totale est atteinte en 1 h pour des tailles de gouttelettes de 60 nm et un contenu en solide de 30 %. L’auto-amorçage photoinduit a permis de générer rapidement une grande quantité de chaînes en croissance au sein des gouttelettes. [...] / Issues and potentials of miniemulsion radical photopolymerization were discussed, starting from monomer miniemulsions’ optical properties to the synthesis of new semi-crystalline polysulfide nanoparticles by thiol-ene reaction. First, the relationship between the optical properties of miniemulsion and the polymerization efficiency was clarified. We established the major role of optical scattering on the acrylate nanodroplets’ photopolymerization kinetic, while the absorption was found to play a minor role. Whether diluted or concentrated medium (Kubelka-Munk model), light scattering is attenuated when droplet size decreased. The corollary is a significant improvement of UV light penetration within the reactor vessel leading to an acceleration of the polymerization kinetics. However, this conclusion was mitigated by the fact that compartmentalization effect could not be easily dissociated from optical effects. Note that in concentrated medium (solids content of 30 wt %), beyond 150 nm droplet diameter, the scattering coefficient leveled off regardless of droplet size. An absorbance drop was observed using UV-visible spectroscopy throughout the irradiation of the smallest acrylate miniemulsions (40 nm). This result suggested a polymerization mechanism occurring by monomer diffusion from non-nucleated droplets to growing particles. This non-invasive analysis (no dilution was required) is of high interest to study the nucleation mechanism.In a second part, we demonstrated that acrylate miniemulsion photopolymerization could be performed through a monomer self-initiation mechanism induced by short-wavelength UV irradiation ( < 300 nm). Such original photochemical initiation avoided the use of photoinitiator, thus limiting the risks associated with their residual presence in the final material. The self-initiated photopolymerizations were carried out in a model microreactor (spectroscopic cell of 0.1 to 1 mm thick). The variation of several parameters allowed us to identify key parameters influencing polymerization kinetics such as droplet size, thus corroborating the results of the optical study. The irradiation wavelength and the optical path played a crucial role; the shift towards shorter wavelengths and the sample thickness reduction accelerated both the generation of initiating radicals and the number of nucleated entities. The versatility of the method was demonstrated by fast polymerization (complete conversion achieved within 20 minutes) employing a wide range of acrylate, methacrylate and vinyl acetate monomers. Regarding the self-initiating mechanism, one proved that the initiating species likely originated from a biradical able to abstract or transfer hydrogen from monomer molecules, thereby forming initiating monoradicals. Through this original mechanism, the generation of radicals was constant throughout the polymerization, which impacted the characteristics of the copolymer chains: the polydispersity index tended to increase and the molar masses decreases when compared with a conventional photoinduced process. These photopolymerizations were also carried out in an annular immersion photoreactor and showed the same trends regarding the effect of droplet size as the experiments conducted in unstirred spectroscopic tank. For example, a complete conversion was reached after 1 h for a 60 nm acrylate miniemulsion with a solids content of 30 wt %. As a result, a self-initiated polymerization can generate rapidly a large amount of insoluble growing polymer chains within the droplets. This unique feature was exploited to overcome Ostwald ripening without the addition of a specific costabilizer. Photochemical self-initiation could also be used to form surfactant-free nanolatex via Pickering-stabilized miniemulsion photopolymerization. Indeed, Laponite clay adsorbed at the surface of the droplets showed an excellent UV transparency up to 200 nm. [...]

Nos últimos anos, a aplicação de tecnologias de manufatura aditiva tem crescido, estendendo seus benefícios para áreas diversas, como saúde, e encurtando o tempo de desenvolvimento de produto. Contudo, são encontrados apenas fabricantes nacionais de versões \"open-source\" de baixo custo de tecnologias de modelagem por fusão deposição (FDM), não existindo desenvolvedor de uma tecnologia nacional. Em função disto, o objetivo principal deste trabalho é apresentar e validar uma nova concepção de processo de fabricação aditiva. Esta proposta consiste na geração seletiva de compósito de celulose e acrílico através de fonte coerente de luz UV. Para isto, foram realizados estudos referentes a duas áreas principais, desenvolvimento de material e validação da concepção de processo proposto. Para o desenvolvimento de material, foram estudados materiais fotopoliméricos a base de acrilatos de forma a ser obtida uma formulação de material adequada para ser validado o processo. Da mesma forma, a seleção do material celulósico empregado foi realizado a partir da caracterização de materiais celulósicos laminados (papéis) comumente encontrados no mercado. Adicionalmente, foi identificado potencial de viabilidade preliminar da proposta ao longo da caracterização do compósito, visto que foi avaliada a aderência entre camadas, resistência mecânica à tração, resistência à água e microestrutura do compósito. Após o desenvolvimento do material, foi desenvolvido o projeto preliminar do equipamento de validação da proposta, assim como a fabricação de um protótipo e sua calibração. Foram realizados estudos de otimização para implementação do projeto do sistema de posicionamento, assim como dimensionamento de \"error Budget\" e custo relativo de equipamento. Foi também desenvolvido sistema de deposição de material polimérico, sistema de polimerização e alimentação de material, sendo realizados estudos de caracterização e validação do processo proposto. Foram identificados os efeitos principais dos principais parâmetros de processo para a largura da linha de polimerização, interferência da formação de compósito para camadas anteriores e, por fim a construção de corpo de prova. Através destes estudos, foi possível identificar a viabilidade funcional da proposta, sendo observadas as vantagens e desvantagens desta nova concepção em relação aos principais processos de fabricação aditiva no mercado. / In recent years, the application of additive manufacturing technologies has grown, extending its benefits to diverse areas such as health, and shortening the time product development. However, national manufacturers are only found to provide versions of open-source and low cost FDM technologies, highlighting the absence of a national technology developer. Due to that, the main goal of this work is to present and evaluate a novel concept of additive manufacturing process. This proposal consists in selectively generate composite of cellulose and acrylic through a coherent UV light source. For this, studies have been conducted concerning two main areas, material development and validation of proposed process. For the development of material, we have studied photopolymeric materials based on acrylates so as to obtain a composition of material suitable for validating the process. Likewise, the selection of cellulosic substrate was made from the characterization of laminated cellulosic materials (sheet of paper) which are commonly found at market. Additionally, we identified the potential feasibility of the proposal along the preliminary characterization the composite, whereas it was evaluated the adhesion between layers, tensile strength, water resistance and microstructure of the composite. After development the material, it was developed a preliminary design of equipment for validation of proposal, in addition to fabricating and calibrating a prototype. Studies were performed to optimize and implement the mechanical design of the positioning system as well as sizing error Budget and relative cost of equipment. It was also developed the systems of poylmerization, photopolymeric material deposition, and feed of substrate, being conducted studies for the characterization and validation of proposed process. We identified the main effects of the main process parameters on the polymerization line width, interference of the formation of composite layers for and previous layers, and the construction of the test ix body. Through these studies, it was possible to identify the functional feasibility of the proposal, being observed the advantages and disadvantages of this novel design in comparison with the main additive manufacturing process in the market.

Neste trabalho foi estudada a influência da adição de quitosana e sílica a monômeros dimetacrílicos, BisEMA e TEGDMA, por meio das técnicas de fotocalorimetria, termogravimetria e análise dinâmico mecânica. Os resultados dos experimentos de fotocalorimetria demonstraram que a quitosana pode aumentar a velocidade de polimerização e o máximo de conversão para alguns sistemas em determinadas concentrações da mesma, já a sílica tem pouco efeito nas reações de fotopolimerização das amostras. Para os experimentos de termogravimetria, a quitosana tem pouca influência na degradação das amostras não alterando significativamente as curvas TGA/DTG, por outro lado a sílica acelerou a degradação térmica das amostras. A avaliação das propriedades mecânicas demonstrou que a quitosana diminui a temperatura de transição vítrea e a resposta elástica dos sistemas não afetando os valores dos módulos de armazenamento e módulos de perda. A sílica apresentou a tendência de aumento de temperatura de transição vítrea e não alteração da resposta elástica das amostras. / In this work we studied the influence of the addition of chitosan and silica in dimethacrylic monomers, BisEMA and TEGDMA, by photocalorimetry, thermogravimetric analysis and dynamic mechanical analysis. The results of photocalorimetry experiments demonstrated that chitosan can increase the polymerization rate and the degree of conversion for some concentrations. Silica has little effect on photopolymerization reactions of samples. For thermogravimetric experiments, chitosan has little influence on the degradation of samples and does a slightly change the TGA / DTG curves, on the other hand silica accelerated thermal degradation of the samples. The evaluation of mechanical properties showed that chitosan reduces the glass transition temperature and elastic response of the samples but does not affect the values of the storage modulus and loss modulus. Silica showed an effect of increasing glass transition temperature and almost no change in the elastic response of the samples.

Made available in DSpace on 2017-07-10T14:57:28Z (GMT). No. of bitstreams: 1 dissertacao marcal final_ apos defesaIpdf.pdf: 991526 bytes, checksum: 320d4a641b2062d25e7dffaef6de5e29 (MD5) Previous issue date: 2015-02-24 / The aim of this study was evaluate the influence of three techniques of photoactivation, in the sorption (SO) and solubility (SL) of three composite resins Filtek Z350 XT, Tetric N-Ceram and IPS Empress Direct. It was prepared 90 specimen (CP) of 8mm of diameter and 1mm of thickness and divided in 9 groups (n=10). The CP were photoactivated by a LED Bluephase device following these techniques: Convencional (CONV); Soft-Start (SS) and Pulse Delay (PA). They were then placed in a desiccator containing silica gel at 37°C and weighed daily until obtainment of a constant mass m1. Then, they were immerse in deionized water for seven days and weighed (m2). The reconditioning of the CP were accomplished following the procedure of m1 until the obtainment of a constant mass (m3). The values of SO and SL was calculated according to ISO 4049 and submitted to the ANOVA test (two-way) followed by the pos hoc of Turkey, p<0.05. There were no significant statistical differences in SO and SL when compared to the photoactivation techniques for all tested resins. In the analysis of SL, no significant statistical differences between the materials and the photoactivation techniques were observed. As for the composite resin Filtek Z350 XT, statistically higher results to other resins was evaluated. It was concluded that the different forms of photoactivation did not influence in the SO and SL of the tested composite resins. / O objetivo deste estudo foi avaliar a influência de três técnicas de fotoativação, na sorção (SO) e solubilidade (SL) de três resinas compostas Filtek Z350 XT ,Tetric N-Ceram e IPS Empress Direct. Foram confeccionados 90 corpos-de-prova (CP) de 8 mm de diâmetro e 1 mm de espessura e divididos em 9 grupos (n=10). Os CP foram fotoativados com o aparelho de luz LED Bluephase seguindo as seguintes técnicas: Convencional (CONV); Soft-Start (SS) e Pulso Atrasado (PA). Em seguida, foram colocados em um dessecador com sílica gel a 37ºC e pesados diariamente até obtenção de uma massa constante m1. Em seguida, foram imersos em água deionizada por sete dias e pesados novamente (m2). O recondicionamento dos CP foi realizado seguindo o procedimento da m1, até obtenção de uma massa constante (m3). Os valores de SO e SL foram calculados de acordo com a ISO 4049 e submetidos ao teste de ANOVA (two-way), seguido do post hoc de Tukey, p<0,05. Não houve diferenças estatisticamente significantes para SO e SL quando as técnicas de fotoativação foram comparadas, para todas as resinas estudadas. Na análise da SL não foram observadas diferenças estatisticamente significativas entre os materiais e técnicas de fotoativação. Já para SO, a resina composta Filtek Z350 XT apresentou resultados estatisticamente mais elevados às demais resinas compostas avaliadas. Foi possível concluir que as diferentes formas de fotoativação não influenciaram na SO e SL das resinas compostas testadas.

Surface functionalization of living cells for cell therapeutics has gained substantial momentum in the last two decades. From encapsulating islets of Langerhans, to cell laden gels for tissue scaffolds, to individual cell encapsulation in thin hydrogels, to surface adhesives and inert surface camouflage, modification of living cell surfaces has a wide array of important applications. Here we use hydrogel encapsulation of individual cells as a mode of protection from mechanical forces for high throughput cell printing, and chemical stimuli for the isolation of rare cells in blood. In the first study, we review methods of surface functionalization and establish a metric of potential target biomarkers for circulating tumor cell (CTC) isolation. For extended applications in cancer detection through a fluid biopsy, common surface antigen densities were quantitatively assessed in relation to peripheral blood mononuclear cells (PBMCs) for potential targets of cell specific encapsulation. We then look to commercialization of our process after considering biopsy volumes and cell therapy dose sizes. Undesired batch-to-batch variation in our in-house synthesized photo-initiator could be eliminated by the use of fluorescein, a commercial fluorochrome of similar initiating power to our current eosin initiating system. Fluorescence and hydrogel generation were compared indicating a fluorescein conjugate has comparable power to that of our in-house conjugated eosin. Parameters involving the number of cells and fluid volumes processed were then analyzed systematically. Key parameters were studied to determine optimal equipment and protocol for clinically relevant batch sizes. The final study looks at the mechanical protection provided by thin hydrogel encapsulation. With growing interests in 3D bioprinting and goals of viable whole organ printing for transplant, high resolution and high throughput printing is a growing need. 3D bioprinting presents intense mechanical stimuli in the process that cells must endure. Here we analyze how hydrogel encapsulation reinforces the cellular membrane allowing cells to withstand the damaging forces associated with bioprinting.

Photopolymerizations offer many advantages (such as temporal and spatial control of initiation, cost efficiency, and solvent-free systems) over traditional thermopolymerization. While they are now well-established as the preferred option for a variety of films and coating applications, they are limited from many applications due to problems such as oxygen inhibition, light attenuation, additive interference, or the creation of shadow regions and oxygen pockets due to complex shapes. These problems can be solved by using an underutilized form of photopolymerization--cationic photopolymerization. Cationic photopolymerizations have unique active centers which are essentially non-terminating causing extremely long active center lifetimes. In this contribution, the unique characteristics of cationic active centers are explored for their ability to be used in many new applications where previous photopolymerization techniques failed. It was found that the long lifetimes of the active centers permitted them to be very mobile, allowing them to migrate into and polymerize regions that were never illuminated in a process termed shadow cure. The mobility of cationic active centers provides a very efficient means of photopolymerizing of thick and pigmented systems. The long lifetimes of the cationic active centers can be used in the creation of a sequential stage curable polymer system and in the development of novel methods to cure complex shapes, two applications previously unattainable by photopolymerization. The termination of the cationic active centers was found to be reversible and can be used as a technique for external temporal control of the photopolymerization after the illumination has ceased. These abilities have great potential and will allow cationic photopolymerization to be used in many new applications where previous photopolymerization techniques failed, expanding their influence and benefits.

Charge transfer (CT) complexes have been used in a number of radiation polymerisation processes including grafting and curing. The complexes studied include donor (D) monomers like vinyl ethers and vinyl acetate (VA) with acceptor (A) monomers such as maleic anhydride (MA). Both UV and EB have been utilised as radiation sources. The complexes are directly grafted to these substrates in the presence of radiation. The complexes yield novel copolymers when radiation cured with concurrent grafting improving the properties of the finished product. The term cure grafting has been proposed for this concurrent grafting process. Studies in basic photografting work to complement the cure grafting have been proposed. The role of solvent in grafting is discussed, particularly the effect of aromatics in photografting to naturally occurring trunk polymers like wool and cellulose. The effect of the double bond molar ratio (DBMR) of the DA components in grafting is examined. The ultraviolet (UV) conditions for gel formation during photografting, hence the importance of homopolymer yields in these processes is reported. A plausible mechanism to explain the results from this photografting work is proposed. The significance of these photografting studies in the related field of curing, especially in UV and ionising radiation (EB) systems, is discussed. EB curing and cure grafting of charge transfer (CT) monomer complexes is investigated. The EB results are compared with UV curing and cure grafting of the same complexes. The work has been extended to include EB/UV curing and cure grafting of thiolene systems. The significance of these results in the potential commercial application of these complexes is discussed. Variables affecting the UV/EB curing and cure grafting of thiolenes on cellulose have been studied. These include effect of varying the type of olefin, increasing the functionality of the thiol, use of acrylate monomers and oligomers in hybrid systems, altering the surface structure of the cellulose and finally the role of air in these processes particularly with EB. Photopolymerisation of the thiol-enes in bulk has also been investigated. The thesis content is based on the published work of 14 research papers over the course of the project. / Doctor of Philosophy (PhD)

In this study / ferrocenyl and naphthalenyl substituted quinoxaline derivatives / 5,8- bis (2,3- dihydrothieno [3,4-b] [1,4] dioxin-5-yl)-2- (naphthalen-2-yl)- 3- ferrocenyl- 4a,8a-dihydroquinoxaline / 5,8- bis (2,3-dihydrothieno [3,4-b] [1,4]dioxin-5-yl) -2- (phenyl) -3-ferrocenylquinoxaline / 5,8-bis (2,3-dihydrothieno [3,4-b] [1,4]dioxin-5-yl) -2,3- di(naphthalen-2-yl)quinoxaline and trihexylthiophene and thiophene coupled benzimidazole derivatives / 4-(tert-butyl)-4,7-bis(4-hexylthiophen-2-yl)spiro[benzo[d]imidazole-2,1-cyclohexane] and 4-(tert-butyl)-4, 7-bis(thiophenyl)spiro[benzo[d]imidazole-2,1-cyclohexane] were used as photosensitizers to broaden the active area of diaryliodonium salts. Both quinoxaline and benzimidazole derivatives are expected to be efficient in cationic photopolymerization with a variety of vinyl and oxide monomers at room temperature upon long wavelength UV irradiation. Photopolymerization will be initiated by diphenyliodonium salts and monitored with Optical Pyrometry. Characterization will be completed with optical absorption, flourescence studies and photopolymerization under solar irradiation.

Mask Projection Stereolithography (MPSLA) is a high resolution manufacturing process that builds parts layer by layer in a photopolymer. In this research, a process planning method to fabricate MPSLA parts with constraints on dimensions, surface finish and build time is formulated. As a part of this dissertation, a MPSLA system is designed and assembled. The irradiance incident on the resin surface when a given bitmap is imaged onto it is modeled as the Irradiance model . This model is used to formulate the Bitmap generation method which generates the bitmap to be imaged onto the resin in order to cure the required layer. Print-through errors occur in multi-layered builds because of radiation penetrating beyond the intended thickness of a layer, causing unwanted curing. In this research, the print through errors are modeled in terms of the process parameters used to build a multi layered part. To this effect, the Transient layer cure model is formulated, that models the curing of a layer as a transient phenomenon, in which, the rate of radiation attenuation changes continuously during exposure. In addition, the effect of diffusion of radicals and oxygen on the cure depth when discrete exposure doses, as opposed to a single continuous exposure dose, are used to cure layers is quantified. The print through model is used to formulate a process planning method to cure multi-layered parts with accurate vertical dimensions. This method is demonstrated by building a test part on the MPSLA system realized as a part of this research. A method to improve the surface finish of down facing surfaces by modulating the exposure supplied at the edges of layers cured is formulated and demonstrated on a test part. The models formulated and validated in this dissertation are used to formulate a process planning method to build MPSLA parts with constraints on dimensions, surface finish and build time. The process planning method is demonstrated by means of a case study.

Benzimidazole and benzotriazole derivatives, 4-(2,3-Dihydrothieno[3,4-b][1,4] dioxin-5-yl)-7-(2,3-dihydrothieno[3,4b][1,4]dioxin-7-yl)-2-benzyl-1H-benzo[d] imidazole (BIm-Ed), 2-benzyl-4,7-di(thiophen-2-yl)-2H-benzo[d] [1,2,3] triazole (BBTS), and 2-benzyl-4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2Hbenzo[ d] [1,2,3] triazole (BBTES) were employed as photosensitizers for diaryliodonium salt photoinitiators in cationic photopolymerization of various epoxide and vinyl ether monomers. Diphenyliodonium hexafluorophosphate (Ph2I+PF6&macr / ) salt was used as the photoinitiator in this study. Extended conjugation and electron-rich moieties of the photosensitizers enabled the use of long wavelength UV and visible light emitting light sources in cationic photopolymerizations. Polymerizations were achieved at room temperature and monitored by optical pyrometry. Photopolymerization of a diepoxide monomer with ambient solar irradiation was examined.