Strong underwater bonds between polycarbonate sheet and various other substrates were achieved using ethyl 2-cyanoacrylate gel cured with an anionic photoinitiator (dibenzoylferrocene). The gel reacts quickly with water on contact and forms a protective polyethyl cyanoacrylate (PECA) skin. This provides a diffusion barrier that protects the inner monomer from further reaction with or polymerisation by water (hydroxide ions). The PECA skin is, however, permeable to water and the inner monomer slowly reacts as water diffuses through the PECA skin. The application procedure for this adhesive is critical because of the fast reaction with water. The adhesive should be applied at the centre of the bond area in such a way as to cover the smallest exposed surface area and that it should not be spread out over the entire surface area. The PECA skin will rupture when the substrates are pressed together, exposing unreacted monomer to the fresh new surface between the two substrates. The adhesive displaces water as it propagates towards the joint edges. In this way it is able to form a strong underwater bond. Without a photoinitiator, ethyl cyanoacrylate adhesives will form strong bonds to smooth underwater surfaces. The addition of a photoinitiator (dibenzoylferrocene), however, increases the rate at which the bond strength develops. Photo differential scanning calorimetric (photo-DSC) analysis was used to determine the optimum photoinitiator concentration. A concentration of between 0.3% (m/m) and 0.1% (m/m) was found to be optimum for adhesive films between 0.5 and 1.2 mm thick. Epoxy-based underwater adhesives have the disadvantage that the cure rate is very slow at low water temperatures. In contrast, the current system features a negative temperature dependence. Therefore, the curing rate is faster at lower water temperatures, making it highly suitable for very cold environmental conditions. The underwater bonding properties of cyanoacrylate adhesive were measured on a wide range of metallic and non-metallic materials. Bond strengths ranged from 1 to 5 MPa respectively. Bond strength (0.2 mm film thickness) develops in a very short time (less than a minute) using a 5 mW/cm2 blue LED light source as trigger for the photo initiator. Water temperatures between 1.5 and 40 °C did not influence the ultimate bond strength achieved following 50 seconds of illumination. The reduction in bond strength due to the ethyl cyanoacrylates reacting with water was measured in artificial sea water and potable water. A 20% reduction in bond strength was found after 10 minutes of water exposure. The underwater bond should therefore be made as soon as possible following exposure to water. Bond ageing studies on both steel and polycarbonate showed an initial decrease in bond strength (during the first 50 hours); thereafter the bond strength stabilises. / Dissertation (MEng)--University of Pretoria, 2011. / Chemical Engineering / unrestricted

La photopolymérisation est une technologie qui gagne de plus en plus d’importance de par ses nombreuses applications et ses énormes avantages par rapport à la polymérisation thermique tels que le respect de l’environnement, des coûts économiques maitrisés car la technologie est mise en œuvre à température ambiante et ne requiert qu’une faible consommation d'énergie. De plus, elle n'utilise pas ou très peu de solvants, d'où la réduction d’émission de produits polluants. Le processus de polymérisation photochimique présente également l’avantage d’être très rapide : en effet les réactions de photopolymérisation sont souvent rapides voire même quasi instantanées. De plus le procédé de polymérisation devient photolatent : la polymérisation impliquant les formulations actives seulement en présence de lumière, la réaction peut être déclenchée « quasi à la demande ». Ce processus chimique nécessite des composants nommés « photoamorceurs », lesquels absorbent la lumière et produisent le démarrage de la réaction de polymérisation. En particulier, le développement de systèmes photoamorceurs capables d’absorber de la lumière visible a un intérêt croissant pour différentes applications industrielles, notamment l’holographie. Dans la cadre de cette thèse, des diverses systèmes photoamorceurs contenant un colorant et un ou deux co-amorceurs, qui après réaction avec les états excités des colorants génèrent les radicaux actifs, ont été étudiés, depuis leurs propriétés photophysiques fondamentales et moléculaires, jusqu’aux applications et performances pour la polymérisation des résines acrylates. Cette thèse est articulée autour de six chapitres. Dans le premier chapitre une introduction et une étude bibliographique des différents systèmes photoamorceurs développés ces dernières années sont présentées et comparés. Les chapitres deux et trois sont consacrés à l’étude des propriétés photochimiques et photophysiques réalisés sur des photoamorceurs absorbant de la lumière ultraviolette et visible respectivement. Les techniques utilisés dans ces chapitres incluent, mais ne sont pas limités à, la spectroscopie d’absorption UV-Vis stationnaire, la fluorescence, la photolyse éclaire (LFP), la fluorescence résolue en temps par comptage de photon unique (TC-SPC), la spectroscopie ultrarapide nanoseconde et femtoseconde, la spectroscopie de résonance paramagnétique électronique (EPR), entre autres. Le chapitre deux porte sur l’étude de la photophysique d’un colorant de type cyanine : l’astrazone Orange R (AO R). La photophysique de ce colorant n’est pas connue et une étude exhaustive a été menée avec des spectroscopies ultra rapides (femtoseconde) ainsi que par modélisation moléculaire. Malgré sa photophysique compliquée ce colorant, fonctionne comme un photoamorceur très efficace dans la région bleue du spectre électromagnétique. Les chapitres suivants forment une deuxième partie de la thèse dédiée à l’étude des mécanismes d’amorçage de photopolymérisation, dont le chapitre quatre aborde le cas d’irradiation le plus « traditionnel », qui est l’irradiation en mode continu (ou CW). Est ensuite abordé l’étude de la polymérisation sous irradiation pulsée ultra-courte : dans cette partie la source d’irradiation continue classique est remplacée par un laser Nd :Yag qui produit des impulsions lumineuses d’une durée de quelques 9-10 nanosecondes. Cette polymérisation avec laser pulsé ou PLP est très originale et sera étudiée par spectroscopie infrarouge à transformée de Fourier résolue en temps (RT-FTIR). Dans le chapitre trois, donc, on retrouve les études réalisés avec différents types de systèmes photoamorceurs visibles. Ainsi, les propriétés des colorants capables d’absorber de la lumière visible à différentes longueurs d’onde ont été étudiées dans des systèmes photoamorceurs à deux et trois composants. / Photopolymerization is a technology that is gaining more and more importance due to its numerous applications and its advantages compared to thermic polymerization. This chemical process requires compounds called photoinitiators, which absorb light and produce the initiation of the radical polymerization. The development of photoinitiating systems (PIS) which are able to absorb visible light have an increasing interest due to its industrial applications, such as holographic recording. During this thesis, many PIS were studied, from its photophysical properties to its application in acrylate polymerization. There are many different types of photoinitiators. The most classical ones are Type I PI, which are molecules that overcome homolytic cleavage from their excited state, generating initiating radicals immediately after photon absorption. Type II PI, in contrast, are composed by two molecules: one that absorbs the photon, and other that will react with the excited state of the first via electron transfer or hydrogen transfer, generating radicals that will be able to initiate polymerization. In last place, there are the most efficient Photocyclic Initiating Systems (PCIS) whose mechanism is more complicated and will be widely discussed within these pages. A state of the art of the PIS available up to date is made in the first chapter. Given the importance of the properties of the molecules involved in the photoinitiating process, the studies of the photophysical properties of a Photoinitiator, the Astrazone Orange (AO), are shown. It was found that this molecule suffers an isomerization process from its excited state, which then comes slowly back to the more stable conformer. This process being viscosity-dependent makes AO a suitable photoinitiator for polymerization with visible light in highly viscous media. The last three chapters of this thesis are devoted to the study of a novel technique called Pulsed Laser Polymerization (PLP). This technique consists in the irradiation of the samples with a short duration pulsed laser, which allows the separation of the initiation steps of the polymerization reaction from the steps of propagation and termination. A simple Type I PI was used as a model to study the properties of this technique of polymerization. The monomer conversion was registered by RT-FTIR and analyzed. To a better understanding of these results, a mathematical model was developed. Thanks to it, it was possible to collect valuable information about propagation and termination rate constants (kp and kt, respectively), the variation of viscosity with conversion and other aspects relatives to PLP mechanism. Furthermore, the efficiency of many visible light PIS was studied by PLP. Their performance was compared and studied and contrasted with the classical continuous irradiation mode (CW). The characteristics that a PIS must have in order to show efficient polymerization in PLP mode were found and discussed. Finally, the effect of formulation viscosity in PLP and CW was analyzed by diluting the sample with different amounts of DMSO. In PLP, it was seen that the highest conversion is found for the most concentrated samples, while the opposite effect is noticed in CW. This result is attributed to the different conditions given by the difference in irradiation methods.

The present work was performed at Sherwin–Williams Sweden group AB with the objective of comparing short-wavelength light emitting diodes (UVB/UVC) with the conventional mercury arc lamp as a curing method of acrylate-based, UV-paint undergoing free-radical polymerization when exposed to UV-radiation. Due to environmental and health risks, mercury-doped radiation sources will be phased out in the near future, according to the United Nations Minamata convention, hence new alternatives are needed. Light-emitting diodes differ from the mercury arc lamp as they provide semi-discrete output intensity lines within the UV spectrum instead of a broad output distribution with several main intensity lines. The power output is also considerably lower compared to the conventional method which limits the irradiance and dose that are key parameters in activating and propagating free-radical polymerization of UV-paint. Seven different light-emitting diodes between 260–320 nm was examinedand compared to the conventional mercury arc lamp. Cured coatings were evaluated by measuring the relative extent of acrylate conversion with ATR-FTIR and micro-hardness indentation test. Both methods correlate to the relative cross-linking density and qualitatively describe the curing process for each radiant source at a specific irradiance and dose. Three different paint formulations with widely different properties were used in the experiments. All three paints were able to cure with one or several light emitting diodes at comparable doses and 10 to 20 times lower irradiance to the conventional mercury arc lamp, resulting in similar acrylate conversion and hardness.

O presente trabalho teve por foco prover uma revisão de conceitos relacionados às resinas dentais fotopolimeráveis e, também, analisar como diferentes concentrações de fotoiniciadores de uso comum em odontologia podem influenciar no desempenho mecânico e na cor de resinas dentais. Concentrações de 0,01%, 0,10%, 0,25% 0,50%, 0,75%, 1,00% e 10% em massa de fotoiniciador foram adicionadas em uma matriz polimérica composta por TEGDMA/BisGMA 50%/50% em massa de forma que, fixando variáveis externas referentes à fonte de luz e à preparação das amostras, foi possível avaliar o efeito da concentração de fotoiniciador nas propriedades mecânicas de resistência à fratura por compressão, resistência à fratura pela aplicação de tensão diametral e dureza Barcol. Por fim, o efeito da concentração na cor aferida através do método CIELab foi investigada. Os fotoiniciadores utilizados foram o Irgacure® 819, a 1-fenil-1,2-propanodiona (PPD) e a Canforoquinona a qual foi utilizada juntamente com ocoiniciador Etil-4 dimetilaminobenzoato (EDB) na concentração constante de 1% em massa. Os resultados mecânicos e de cor foram comparados entre as diferentes amostras através de análises estatísticas (ANOVA) e, especificamente para cor, o parâmetro de diferença de cor (ΔE) foi interpretado verificar se as alterações observadas são perceptíveis ao olho humano. Para fundamentar os estudos, análises do espectro de absorção das amostras, do espectro de irradiação da fonte de luz e do grau de conversão das amostras foram realizadas. Os resultados revelaram que, independentemente do fotoiniciador, graus de conversão da mesma ordem de grandeza de um adesivo comercial foram obtidos, porém as velocidades de reação foram diferentes (maior velocidade para as amostras de CQ e menor para PPD). Curvas características foram obtidas para os espectros de absorção e de irradiação confirmando, pela sobreposição das curvas, que a fonte de luz é efetiva para iniciação da polimerização das amostras. As análises de resistência à fratura revelaram que a quebra catastrófica do material ocorrerá preferencialmente quando a força é aplicada ao longo do diâmetro para os corpos de prova preparados. Quanto à dureza, verificou-se que que para a CQ houve um máximo, para Irgacure um comportamento assintótico com aumento da concentração e, para a PPD, não foi possível a obtenção de amostras (verificado que a PPD necessita de tempo de irradiação superior ao convencionalmente utilizado na prática odontológica). Os testes de ANOVA permitiram verificar que o Irgacure é capaz de fornecer resultados mecânicos semelhante em relação à CQ ocasionando, em contrapartida, um menor escurecimento e amarelamento. Analisando o parâmetro ΔE, confirmou-se que a alteração na cor se torna evidente à medida que ocorre o aumento da concentração de fotoiniciador independentemente do fotoiniciador utilizado, porém a alteração é maior para a CQ. / The focused of the present work was conduct a concept review of the photochemical dental restoratives (resins) state-of-art and, also, evaluate the influence of photoinitiator concentration in mechanical behavior and shade. Different quantities of photoinitiators (0,01%, 0,10%, 0,25%, 0,50%, 0,75%, 1,00% and 10% wt.) were added in a resin based prepared of TEGDMA/BisGMA (50%/50% wt./wt.) to inspect the effect of the photoinitiator load in the diametral tensile strength (DTS), compressive strength (CS), Barcol hardness and, also, in the color perception measured by CIELab test method. The photoinitiatorsused were the Irgacure. 819, the Phenil-propanodione (PPD) and the Camphoroquinone (CPQ), which was used with EDB (1% in weigh) as a coinitiator. The mechanical properties were compared between the different concentrations and photoinitiators using ANOVA statistical analysis. For color, the different samples was compared using the parameter ΔE. Finally, the absorption spectrum and the degree of conversion for each concentration was obtained to support the experimental tests. Results showed that, independently of the photoinitiator used, degrees of conversion similar with a commercial adhesive were obtained, but the polymerization rate were different (higher for the CPQ samples and lower for PPD). The absorption spectra of samples were obtained and the overlap with the 3M ESPE LED irradiation curve confirmed the effectiveness of the light source to promote the initiation of the polymerization process. Mechanical results analysis showed that the catastrophic breakdown of the material occurs preferentially when the force is applied along the diameter (DST tests) in the prepared specimens. Regarding hardness, different behavior could be perceived: i) a curve with a maximum point occur for CPQ, ii) for Irgacure. 819 an asymptotic curve was obtained with the photoinitiatorconcentration growth and, finally, iii) no curve was obtained for PPD once for PPD it was realized that is required an irradiation time higher than the conventional 20s used in the clinical interventions and, also, higher than the methodology used in the present work. ANOVA tests showed that Irgacure. 819 samples could provide similar mechanical performance compared CPQ but, on the other hand, lower color variation with the concentration growth. The parameter ΔE confirmed that the color change becomes more noticeable as an increase in photoinitiator concentration occurs regardless of photoinitiator used, but the color variation is much higher in CQ compared with the other systems.

O presente trabalho teve por foco prover uma revisão de conceitos relacionados às resinas dentais fotopolimeráveis e, também, analisar como diferentes concentrações de fotoiniciadores de uso comum em odontologia podem influenciar no desempenho mecânico e na cor de resinas dentais. Concentrações de 0,01%, 0,10%, 0,25% 0,50%, 0,75%, 1,00% e 10% em massa de fotoiniciador foram adicionadas em uma matriz polimérica composta por TEGDMA/BisGMA 50%/50% em massa de forma que, fixando variáveis externas referentes à fonte de luz e à preparação das amostras, foi possível avaliar o efeito da concentração de fotoiniciador nas propriedades mecânicas de resistência à fratura por compressão, resistência à fratura pela aplicação de tensão diametral e dureza Barcol. Por fim, o efeito da concentração na cor aferida através do método CIELab foi investigada. Os fotoiniciadores utilizados foram o Irgacure® 819, a 1-fenil-1,2-propanodiona (PPD) e a Canforoquinona a qual foi utilizada juntamente com ocoiniciador Etil-4 dimetilaminobenzoato (EDB) na concentração constante de 1% em massa. Os resultados mecânicos e de cor foram comparados entre as diferentes amostras através de análises estatísticas (ANOVA) e, especificamente para cor, o parâmetro de diferença de cor (ΔE) foi interpretado verificar se as alterações observadas são perceptíveis ao olho humano. Para fundamentar os estudos, análises do espectro de absorção das amostras, do espectro de irradiação da fonte de luz e do grau de conversão das amostras foram realizadas. Os resultados revelaram que, independentemente do fotoiniciador, graus de conversão da mesma ordem de grandeza de um adesivo comercial foram obtidos, porém as velocidades de reação foram diferentes (maior velocidade para as amostras de CQ e menor para PPD). Curvas características foram obtidas para os espectros de absorção e de irradiação confirmando, pela sobreposição das curvas, que a fonte de luz é efetiva para iniciação da polimerização das amostras. As análises de resistência à fratura revelaram que a quebra catastrófica do material ocorrerá preferencialmente quando a força é aplicada ao longo do diâmetro para os corpos de prova preparados. Quanto à dureza, verificou-se que que para a CQ houve um máximo, para Irgacure um comportamento assintótico com aumento da concentração e, para a PPD, não foi possível a obtenção de amostras (verificado que a PPD necessita de tempo de irradiação superior ao convencionalmente utilizado na prática odontológica). Os testes de ANOVA permitiram verificar que o Irgacure é capaz de fornecer resultados mecânicos semelhante em relação à CQ ocasionando, em contrapartida, um menor escurecimento e amarelamento. Analisando o parâmetro ΔE, confirmou-se que a alteração na cor se torna evidente à medida que ocorre o aumento da concentração de fotoiniciador independentemente do fotoiniciador utilizado, porém a alteração é maior para a CQ. / The focused of the present work was conduct a concept review of the photochemical dental restoratives (resins) state-of-art and, also, evaluate the influence of photoinitiator concentration in mechanical behavior and shade. Different quantities of photoinitiators (0,01%, 0,10%, 0,25%, 0,50%, 0,75%, 1,00% and 10% wt.) were added in a resin based prepared of TEGDMA/BisGMA (50%/50% wt./wt.) to inspect the effect of the photoinitiator load in the diametral tensile strength (DTS), compressive strength (CS), Barcol hardness and, also, in the color perception measured by CIELab test method. The photoinitiatorsused were the Irgacure. 819, the Phenil-propanodione (PPD) and the Camphoroquinone (CPQ), which was used with EDB (1% in weigh) as a coinitiator. The mechanical properties were compared between the different concentrations and photoinitiators using ANOVA statistical analysis. For color, the different samples was compared using the parameter ΔE. Finally, the absorption spectrum and the degree of conversion for each concentration was obtained to support the experimental tests. Results showed that, independently of the photoinitiator used, degrees of conversion similar with a commercial adhesive were obtained, but the polymerization rate were different (higher for the CPQ samples and lower for PPD). The absorption spectra of samples were obtained and the overlap with the 3M ESPE LED irradiation curve confirmed the effectiveness of the light source to promote the initiation of the polymerization process. Mechanical results analysis showed that the catastrophic breakdown of the material occurs preferentially when the force is applied along the diameter (DST tests) in the prepared specimens. Regarding hardness, different behavior could be perceived: i) a curve with a maximum point occur for CPQ, ii) for Irgacure. 819 an asymptotic curve was obtained with the photoinitiatorconcentration growth and, finally, iii) no curve was obtained for PPD once for PPD it was realized that is required an irradiation time higher than the conventional 20s used in the clinical interventions and, also, higher than the methodology used in the present work. ANOVA tests showed that Irgacure. 819 samples could provide similar mechanical performance compared CPQ but, on the other hand, lower color variation with the concentration growth. The parameter ΔE confirmed that the color change becomes more noticeable as an increase in photoinitiator concentration occurs regardless of photoinitiator used, but the color variation is much higher in CQ compared with the other systems.

Cimentos resinosos experimentais contendo diferentes sistemas fotoiniciadores apresentaram propriedades físicas semelhantes ou superiores a cimentos resinosos convencionais sob efeito de diferentes tipos de fonte de luz. Objetivo: Analisar o espectro de diferentes fontes de luz e sistemas fotoiniciadores e sua influência nas propriedades físicas de cimentos resinosos quando ativados, através de um anteparo cerâmico, por fontes de luz halógena e LED. Metodologia: Cimentos resinosos experimentais contendo uma mistura de BisGMA, TEGDMA (50wt%) e partículas de carga silanizadas (65wt%), foram preparados com o uso dos fotoiniciadores Canforoquinona (CQ), Fenil Propanodiona (PPD) e Óxido bis-alquil fosfínico (BAPO) de forma isolada e combinados. Os co-iniciadores utilizados foram Difenil Iodônio (DFIHFP) e a amina terciária DMAEMA. As fontes de luz utilizadas foram: lâmpada halógena (XL 2500) e duas fontes de diodo emissor de luz - LED (FreeLigth 2 e Bluephase). Um anteparo cerâmico (IPS e.max Press) apresentando 13,0mm x 1,0mm de espessura foi utilizado durante os testes. Amostras com 7,0mm x 2,0mm x 1,0mm foram confeccionadas (n=360). A avaliação do Grau de Conversão (GC) dos cimentos experimentais foi realizada por Espectroscopia de Infravermelho Transformada de Fourier (FTIR), sendo em seguida submetidas ao teste de resistência à mini-flexão, módulo flexural e microdureza Knoop. Os resultados obtidos em todos os testes foram submetidos à análise de variância dois fatores - ANOVA e teste de Tukey (5%). Resultados: A associação do DFIHFP aos fotoiniciadores aumentou as propriedades avaliadas de todos os cimentos experimentais independente da fonte de luz (FL) utilizada. O fotoiniciador BAPO apresentou resultados superiores ou iguais estatisticamente em comparação ao grupo controle (CQ/amina), independente da FL utilizada. Conclusão: A utilização de sistemas iniciadores e co-iniciadores alternativos possibilita a obtenção de propriedades superiores ou iguais ao sistema convencional, tornando-se um sistema promissor para atuar de forma isolada ou associada. / Resin cements containing different experimental photoinitiators systems present physical properties similar to or better than conventional resin cements under the effect of different types of light source. Objective: To analyze the spectrum of different light sources and systems photoinitiators and their influence on physical properties of resin cements when activated through a bulkhead ceramic, halogen light sources and LED. Methodology: experimental resin cements containing a mixture of BisGMA, TEGDMA (50wt%) and silanized filler particles (65wt%) were prepared with the use of photoinitiators camphorquinone (CQ), phenyl oxide bis-propanedione (PPD) and alkyl phosphinic (BAPO) separately and combined. The primers used were co-diphenyl iodonium (DFIHFP) tertiary amine and DMAEMA. The light sources used were: halogen lamp (XL 2500) and two sources of light emitting diode - LED (FreeLigth bluephase and 2). A ceramic shield (IPS e.max Press) having 13.0mm x 1.0mm thick was used for testing. Samples with 7.0mm x 2.0mm x 1.0mm were fabricated (n=360). The evaluation of the degree of conversion (GC) of experimental cements was performed by Infrared Spectroscopy Fourier Transform, and then to test for resistance to mini-bending, flexural modulus and microhardness. The results in all tests were subjected to two-factor analysis of variance - ANOVA and Tukey test (5%). Results: The combination of photoinitiators DFIHFP to improve board properties of all the experimental cements independent light source (LCU) used. The photoinitiator BAPO showed statistically equal or better results compared to the control group (CQ / amine), regardless of LCU used. Conclusion: The use of systems co-initiators and initiators to obtain alternative provides equal or better properties to the conventional system, making it a promising system to act in isolation or in combination.

Ce travail de thèse aborde l’étude mécanistique de systèmes photoamorceurs complexes et la modélisation cinétique du processus de photopolymérisation. Dans un premier temps, le mécanisme photochimique d’un système combinant le [Ru(bpy)3]2+ et des agents RAFT pour l’amorçage et le contrôle d’un processus radicalaire a été étudié. Un transfert d’énergie a été clairement démontré, contredisant le mécanisme de transfert d’électron généralement proposé. Un système photoamorceur à 3 composants bicyclique dual ITX/IOD+/RSH a ensuite été considéré pour la synthèse de matériaux hybrides organiques-inorganiques. Sous excitation lumineuse, ce système produit simultanément des radicaux et des protons, permettant d’amorcer, respectivement, des processus de polymérisation radicalaire et sol-gel. Dans un second temps, l’interdépendance entre les cinétiques de photopolymérisation et l’évolution des propriétés du milieu réactionnel a été étudiée par le biais du développement d’un modèle cinétique permettant la simulation de l’intégralité du processus de photopolymérisation. Des systèmes photoamorceurs de complexité croissante ont été inclus afin d’étudier les spécificités de leurs cinétiques. Un système de type I a permis de mettre en évidence les modes de terminaison majoritaires et leur évolution au cours de la synthèse des polymères, tandis que le rôle non négligeable du transfert d’électron inverse a été mis en exergue pour des systèmes photoamorceurs de type II. La fonction d’agent de terminaison d’un photoproduit issu d’un colorant cationique, ainsi que certaines spécificités des systèmes photocycliques à 3 composants, ont été finalement étudiés grâce à la modélisation. / This thesis deals with the mechanistic study of complex photoinitiating systems and the kinetic modeling of the photopolymerization process. In a first time, the photochemical mechanism of a system combining [Ru(bpy)3]2+ and RAFT agents for the initiation and control of a radical process has been studied. An energy transfer has been clearly demonstrated, contradicting the electron transfer mechanism generally proposed. A dual bicyclic three-component photoinitiating system ITX/IOD+/RSH has been considered for the synthesis of organic-inorganic hybrid materials. Under light exposure, this system produces simultaneously radicals and protons, enabling the initiation of a radical polymerization and a sol-gel process, respectively. In a second time, interdependence between photopolymerization kinetics and evolution of the medium’s properties has been studied, through developing a kinetic model for the simulation of the whole photopolymerization process. Photoinitiating systems of growing complexity have been included in order to study specificities of their kinetics. A type-I system has shown major termination modes and their evolution during the polymer synthesis, while the non-negligible role of back electron transfer has been highlighted for type-II photoinitiating systems. Role of terminating agent of a photoproduct based on a cationic dye, as well as some specificities of photocyclic three-component systems, have been finally studied with the model.

This master's thesis deals with a present problem of alternative dental fillings, which should replace amalgam fillings. Although there are health concerns about these alternative materials, especially resin composite fillings raise concerns, because they release potentionally harmful substances into the oral cavity. Accordingly even this medical device subjects various tests before releasing to the commercial market and one of these tests was carried out according to ČSN EN ISO 10993 and available scientific literature in the experimental part of this thesis. The amalgam controversy, substances used for manufacturing of resin dental fillings and analytical methods are described in the theoretical part of the thesis. In the experimental part of the thesis, 30 days long cumulative extraction experiments were carried out into various extraction mediums in order to assess suitability of new dental resin filling from ADM, a.s. by comparison with commercially available dental material from company GC EUROPE N.V. These samples were analysed by LC-MS and the amount of eluted substances from dental composites to extraction medium was quantified.