<p> Polymerization of bulk styrene initiated thermally as well as with di-tertiary-butyl peroxide was studied in isothermal batch reactors. Thermal polymerization was carried out at 100, 140, 170 and 200°C while polymerization with di-tertiary butyl peroxide was at 100 and 140°C. A kinetic model was derived therefrom accounting for initiation reactions from a first order decomposition of catalyst and a second order reaction between two monomer molecules to form two monoradicals, propagation, chain transfer to monomer and termination by combination only. Gel effect was allowed by the variation of rate constants with conversion. Both the thermal initiation rate constant and the first order decomposition rate constant of di-tertiary butyl peroxide were found to agree with literature values with the present values slightly higher. The initial rate constants for propagation, chain transfer to monomer, and termination were extrapolated to the range, 100-200°C using literature data. This kinetic model was used in the simulation of polymer reactor systems studying the effect of recycle and operating conditions on the molecular weight distribution and rate of production of polymer products.</p> <p> The main body of this thesis reports the polymerization study and the development of the kinetic model. The details of the kinetic equations and methods of solution, experimental techniques involved, and the simulation of polymer reactor systems are reported in the Appendices.</p> / Thesis / Doctor of Philosophy (PhD)

Abstract This work investigates the kinetics of the emulsion polymerization of vinyl acetate. Several aspects of this system have been clarified, including the induced decomposition of persulfate, retardation by oxygen and entry by, and analysis of, the aqueous phase oligomeric radicals. It has been shown that the retardation period observed in the emulsion polymerization of VAc can be explained by the effect of traces of oxygen (< 10-6 M) on the entry efficiency of the initiator-derived aqueous-phase oligomeric radicals. Comparison of rates of polymerization in V and persulfate -initiated polymerizations together with electrospray mass spectrometry of aqueous phase oligomers, has shown that the mechanism for the induced decomposition of persulfate by vinyl acetate is chain transfer to initiator from aqueous-phase oligomeric radicals. A value has been determined for the rate coefficient for transfer to initiator, by fitting literature data to a model based on this mechanism. The reported independence of the rate of polymerization from the monomer concentration in the emulsion polymerization of vinyl acetate has been investigated. Possible explanations for this behaviour have been proposed and tested in this work, by measuring radical-loss rates directly with y-relaxation techniques. Although the Y relaxations were found to be affected by experimental artefacts, it has been demonstrated that rapid exit is not responsible for the high radical-loss rates in this system. The major artefact identified in the y relaxations was the significant effect of relatively small exotherms on relaxation behaviour, Methodologies were developed for correcting affected data and for avoiding exotherms under certain conditions. Arrhenius parameters were determined for the rate coefficient for chain transfer to monomer using the In^M method, which utilises the whole MWD. This section of the work is incomplete, for reasons detailed in chapter 5. However, as a preliminary indication it was found that the frequency factor was 106.38 M-1 s-1 and the activation energy was 38.8 kJ mol-1.

In recent years there have been many efforts to develop and expand the ability of mathematical models capable of describing polymerization systems. Models can provide a key competitive advantage for the industry and research in terms of production and technology development. As new resins are continuously produced to meet the requirement of final applications and processability, it is imperative to pursue strong polymer characterization with special attention to detailed analysis of polymer microstructure. The microstructure of polyolefin is defined by its distribution of molecular weight, chemical composition, branching topology, and stereoregularity. <br /><br /> In this work, a Monte Carlo simulation model was developed to describe the polymerization mechanisms of olefin homopolymerization and copolymerization using single-site coordination catalyst. The mathematical model is meant to describe molecular weight and chemical composition distribution in copolymerization system. More specifically, this research work gives a detailed study of the molecular structure for ethylene- alfa-olefin copolymer. <br /><br /> The chemical and physical properties of copolymers are influenced not only by their average composition, but also by the monomer sequence distribution along the polymer chains. Predicting the molecular weight and comonomer distributions can lead to a better understanding of the possible morphology in solid stated because they are considered to be the main structural parameters that affect the crystallinity of polymeric materials. As a consequence, final physical properties such as the tensile properties of a copolymer could be controlled by the ratio of crystalline species in the polymer. <br /><br /> This work is considered to be a useful tool that enables us to understand and explore specific polymerization catalytic system. Being able to describe the short chain branching and the monomer sequence distribution as a function of chain length enables us to have a better control over semi-batch polymerization reactors.

In recent years there have been many efforts to develop and expand the ability of mathematical models capable of describing polymerization systems. Models can provide a key competitive advantage for the industry and research in terms of production and technology development. As new resins are continuously produced to meet the requirement of final applications and processability, it is imperative to pursue strong polymer characterization with special attention to detailed analysis of polymer microstructure. The microstructure of polyolefin is defined by its distribution of molecular weight, chemical composition, branching topology, and stereoregularity. <br /><br /> In this work, a Monte Carlo simulation model was developed to describe the polymerization mechanisms of olefin homopolymerization and copolymerization using single-site coordination catalyst. The mathematical model is meant to describe molecular weight and chemical composition distribution in copolymerization system. More specifically, this research work gives a detailed study of the molecular structure for ethylene- alfa-olefin copolymer. <br /><br /> The chemical and physical properties of copolymers are influenced not only by their average composition, but also by the monomer sequence distribution along the polymer chains. Predicting the molecular weight and comonomer distributions can lead to a better understanding of the possible morphology in solid stated because they are considered to be the main structural parameters that affect the crystallinity of polymeric materials. As a consequence, final physical properties such as the tensile properties of a copolymer could be controlled by the ratio of crystalline species in the polymer. <br /><br /> This work is considered to be a useful tool that enables us to understand and explore specific polymerization catalytic system. Being able to describe the short chain branching and the monomer sequence distribution as a function of chain length enables us to have a better control over semi-batch polymerization reactors.

Abstract This work investigates the kinetics of the emulsion polymerization of vinyl acetate. Several aspects of this system have been clarified, including the induced decomposition of persulfate, retardation by oxygen and entry by, and analysis of, the aqueous phase oligomeric radicals. It has been shown that the retardation period observed in the emulsion polymerization of VAc can be explained by the effect of traces of oxygen (< 10-6 M) on the entry efficiency of the initiator-derived aqueous-phase oligomeric radicals. Comparison of rates of polymerization in V and persulfate -initiated polymerizations together with electrospray mass spectrometry of aqueous phase oligomers, has shown that the mechanism for the induced decomposition of persulfate by vinyl acetate is chain transfer to initiator from aqueous-phase oligomeric radicals. A value has been determined for the rate coefficient for transfer to initiator, by fitting literature data to a model based on this mechanism. The reported independence of the rate of polymerization from the monomer concentration in the emulsion polymerization of vinyl acetate has been investigated. Possible explanations for this behaviour have been proposed and tested in this work, by measuring radical-loss rates directly with y-relaxation techniques. Although the Y relaxations were found to be affected by experimental artefacts, it has been demonstrated that rapid exit is not responsible for the high radical-loss rates in this system. The major artefact identified in the y relaxations was the significant effect of relatively small exotherms on relaxation behaviour, Methodologies were developed for correcting affected data and for avoiding exotherms under certain conditions. Arrhenius parameters were determined for the rate coefficient for chain transfer to monomer using the In^M method, which utilises the whole MWD. This section of the work is incomplete, for reasons detailed in chapter 5. However, as a preliminary indication it was found that the frequency factor was 106.38 M-1 s-1 and the activation energy was 38.8 kJ mol-1.

Este estudo teve como objetivo investigar múltiplos aspectos relacionados a polimerização da resina composta como: o grau de conversão monomérica (GC), parâmetros da cinética de polimerização e a determinação de monômeros residuais TEGDMA e BisGMA, além de avaliar o desempenho de aparelhos fotoativadores. As resinas compostas experimentais foram manipuladas variando-se os fotoiniciadores R1-) canforoquinona/amina, R2-) PPD/amina, R3-) PPD + canforoquinona/amina) e foram utilizados dois aparelhos para a fotoativação (I-) lâmpada halógena (Demetron LC/ SDS Kerr-USA) e II-) LED (Poly 600/Kavo-Brasil) ambos com 600 mW cm-2, por 40 s. O GC após 300 s e os parâmetros de cinética como taxa máxima de conversão (Rpmáx), tempo em que ocorreu a taxa máxima de polimerização (tmáx) e a conversão quando ocorreu a Rpmáx, foram determinados por meio de espectroscopia de absorção no infravermelho em tempo real (RT-FTIR), Os espectros foram coletados dos espécimes (n=5) no modo cinética, durante 305 s, entre 1680 e 1550 cm-1. As 5 primeiras varreduras coletadas serviram para fornecer o espectro de absorção da resina não polimerizada (utilizado no cálculo do GC). Na 6&ordm; varredura, o fotoativador foi ligado (por 40 segundos) enquanto o espectro continuava a ser coletado até 300 s após a ativação da luz. A presença de monômeros residuais (TEGDMA e BisGMA) foi avaliada por meio da cromatografia líquida de alta eficiência (HPLC), sendo que os espécimes (n=6) foram imersos em acetonitrila (5 mL-24 h) com agitação mecânica, o método desenvolvido utilizou: HPLC, coluna C18, fase móvel A: água com trietilamina (0,05%) acidificada com ácido acético (pH 4) e B: acetonitrila, modo de eluição com gradiente (40-85%-17 min/ 55&deg;C), fluxo de 1 mL min-1, detector UV em 210 nm, injeção de 20 &micro;L. Em relação aos resultados de GC após 300 s os maiores valores foram para a resina R1 tanto fotoativada com LED (65,90% &plusmn;1,81) quanto com a lâmpada halógena (64,40% &plusmn;0,83), e os menores valores encontrados foram quando a resina R2 foi fotoativada pelo LED (35,64% &plusmn;1,73) e a única resina que apresentou diferenças significantes em relação as fontes de luz foi a R2. Os valores da Rpmáx diminuíram nas resinas que apresentavam o fotoiniciador PPD. O tempo de ocorrência da taxa máxima de conversão (tmáx) aconteceu mais rapidamente para a resina com CQ. Todas as resinas apresentaram valores de grau de conversão similares no tmáx. Em relação aos resultados de HPLC, a quantidade de monômeros extraídos (M/M%) variou de 1,98% &plusmn;0,16 à 3,34% &plusmn;0,07 para os monômeros TEGDMA e de 3,57% &plusmn;0,30 à 7,57% &plusmn;0,40 para os monômeros BisGMA. A resina R2 apresentou a maior quantidade de monômeros residuais quando fotoativada com ambas as fontes, principalmente quando fotoativada com o LED. As resinas R1 e R3 obtiveram comportamento parecidos para ambos fotoativadores. Conclui-se que a resina R3 pode ser uma boa opção, pois quando comparada com a resina R1 apresentou vantagens como: redução na Rpmáx, bem como o momento em que esta ocorreu (tmáx), além de ser adequadamente fotoativada com aparelhos de LED. / This study aimed to investigate multiple aspects of composite resin polymerization as the degree of monomer conversion (DC), the kinetic parameters of polymerization and the determination of residual monomers TEGDMA and BisGMA, and evaluate the performance of light curing units. The experimental composites were manipulated by varying the photoinitiators R1-) camphorquinone/amine, R2-) PPD/amine, R3-) PPD + camphorquinone/ amine) and two devices were used for the polymerization I-) halogen lamp (Demetron LC / SDS Kerr, USA) and II-) LED (Poly 600/Kavo-Brasil) both with 600 mW cm-2 for 40 s. DC after 300 s and the kinetic parameters such as maximum rate of polymerization conversion (Rpmax), time of occurrence of the maximum rate of polymerisation (tmax) and the conversion occurred when Rpmax were determined by infrared absorption spectroscopy in real time (RT-FTIR), the infrared spectrum was collected from the specimen (n=5) in order kinetics for 305 s, between 1680 and 1550 cm-1. The first 5 scans were used to provide the collected absorption spectrum of the uncured resin (calculated DC). In the sixth scan, the curing unit was connected (by 40 seconds) while the spectrum continued to be collected up to 300 s after activation of the light. The presence of residual monomers (TEGDMA and BisGMA) was assessed by high performance liquid chromatography (HPLC), and the specimens (n=6) were immersed in acetonitrile (5 mL-24 h) with mechanical stirring, the method developed used: HPLC, C18 column, mobile phase A: water with triethylamine (0,05%) acidified with acetic acid (pH 4) and phase B: acetonitrile, gradient elution mode (40-85% -17 min/55 &deg;C), flow 1 mL/min, UV detector at 210 nm, injection of 20 &micro;L. Regarding the results of DC after 300s were the highest values for both R1 resin polymerized with LED (65.90% &plusmn;1.81) and with a halogen lamp (64.40% &plusmn;0.83), and lower values when the resin was found that R2 was polymerized by LED (35.64% &plusmn;1.73) and the only resin that showed significant differences in the sources of light was the R2. The values of the resins decreased Rpmax who had PPD photoinitiator. The time of occurrence of the maximum rate of conversion (tmax) occurred more rapidly for the resin with CQ. And all resins showed values similar degree of conversion in tmax. For HPLC results, the amount of monomer extracted (M/M%) ranged from 1.98% &plusmn;0.16 to 3.34% &plusmn;0.07 for the monomers of TEGDMA and 3.57% &plusmn;0.30 to 7.57% &plusmn;0.40 for the monomers BisGMA. Resin R2 showed the highest amount of residual monomers as polymerized with both sources, especially when polymerized with LED. Resins R1 and R3 had similar behavior for both curing units. In conclusion, the resin R3 can be a good choice, as compared with the resin obtained R1 advantages as reduction in Rpmax as well as the time it occurred (tmax), and be suitably photoactivated with LED devices.

OBJETIVO: caracterizar a interação entre tensão e cinética de polimerização e seus parâmetros determinantes, e avaliar a qualidade da rede polimérica e propriedades mecânicas de compósitos comerciais para dentes posteriores a base de dimetacrilato ou de silorano. A cinética de polimerização foi avaliada sob influência da intensidade da fonte de luz, da temperatura e da umidade. Por fim, o grau de conversão (GC) do compósito a base de silorano foi avaliado por espectroscopia e titulação. MÉTODOS: foram utilizados três compósitos de baixa contração: Kalore (KAL - GC America) e N´Durance (NDUR Septodont), a base de dimetacrilatos; e Filtek P90 (P90 - 3MESPE), a base de silorano. O EsthetX HD (EHD - Dentsply) foi utilizado como controle. A tensão de polimerização (TP) dos espécimes (n = 5; Ø = 5 mm; h = 1 mm, 10 min) foi obtida em máquina universal de ensaios mecânicos. A contração volumétrica (CVol) foi determinada em linômetro (n = 3; Ø = 6 mm; h = 1,5 mm; 10 min). O módulo de elasticidade em flexão (MeFlex) e a resistência à flexão (RFlex) (n = 10; 10 x 2 x 1 mm) foram obtidos através do teste de dobramento em três pontos (8 mm entre apoios; 0.5 mm/min). O GC e a taxa de polimerização (Rp) dos espécimes (n = 3; Ø = 6,5 mm; h = 0,8 mm) foram determinados por espectroscopia no NIR (banda em 6165 cm-1 para dimetacrilatos e em 4156 cm-1 e 4071 cm-1 para silorano). Para os testes acima descritos, a fotopolimerização foi realizada com 740 mW/cm2 x 27 s (Bluephase G2 Ivoclar). A temperatura de transição vítrea (Tg), a tangente de delta (tan delta), o grau de heterogeneidade e a densidade de ligações cruzadas de espécimes (n = 3; 15 x 3 x 1 mm) com o máximo de conversão foram obtidos em analisador dinâmico-mecânico. A análise dos extratos obtidos após imersão dos espécimes (Ø = 12 mm; h = 0,8 mm; 970 mW/cm2 x 30 s) em diclorometano foi realizada através de 1H-NMR para verificar monômeros residuais. A cinética de polimerização de espécimes (n = 3; Ø = 5,5 mm; h = 1 mm) de todos os materiais, fotopolimerizados com Acticure 4000 EXFO e filtro 320-500 nm, foi analisada sob variação de irradiância (3, 30 ou 200 mW/cm2) e de temperatura (23, 35 ou 60 °C) por espectroscopia no NIR (banda em 6165 cm-1 para dimetacrilatos e em 4156 cm-1 para silorano). A influência da umidade a 23, 35 ou 60 °C na cinética de polimerização foi verificada para Filtek P90 e EsthetX HD. Para auxiliar na identificação de bandas que possam ser utilizadas para o GC do Filtek P90, as conversões de bandas referentes a anéis epóxicos selecionadas com a caracterização espectroscópica (Mid-IR e NIR) de monômeros modelos e do Filtek P90 sem carga foram comparadas com os valores encontrados no teste de titulação ácido-base desses materiais. Os dados dos testes laboratoriais, quando necessário, foram submetidos à Anova e ao Teste de Tukey ( < 0,05). RESULTADOS: O EHD apresentou a maior TP, estatisticamente semelhante ao NDUR e maior que o KAL e o P90, estatisticamente semelhantes. A Cvol do EHD foi superior à do NDUR, e o P90 e o KAL obtiveram os menores valores, estatisticamente semelhantes. O P90 apresentou o maior MeFLex, sem diferença entre os outros materiais. O EHD obteve o maior valor de RFlex, e o KAL e o NDUR apresentaram os menores valores, sem diferença entre eles. O NDUR apresentou o maior GC, seguido do EHD e KAL, e o P90 apresentou o menor valor. O EHD apresentou a maior Tg, seguido de P90, KAL e NDUR. O NDUR e o P90 apresentaram, respectivamente, a maior e a menor tan delta. O NDUR e o KAL apresentaram a maior e a menor homogeneidade, respectivamente. O P90 apresentou a maior densidade de ligações cruzadas, sem diferença entre os outros compósitos. Diferentemente do EHD e do KAL, o P90 e o NUR não apresentaram lixiviação de monômeros residuais. O P90 mostrou cinética de polimerização semelhante aos compósitos dimetacrilatos, inclusive sob variação de irradiância e temperatura. A umidade aumentou ligeiramente o GCMáx do EHD a 23 e a 35 °C, porém a temperatura exerceu maior influência à 60° C. De uma maneira geral, a umidade não influenciou a cinética de polimerização do P90. Em Mid-IR, o P90 apresentou 60 % de conversão através da banda em 883 cm-1, próximo ao valor obtido com a titulação. Já em NIR, há conversão em duas bandas distintas: em 4156 cm-1 (42%) e em 4071 cm-1 (65%). CONCLUSÃO: o GC exerceu grande influência sobre os valores de TP. Altos valores de MeFlex e RFlex foram associados à alta densidade de ligações cruzadas. P90 e NDUR não apresentaram lixiviação de monômeros residuais. Um maior GC é obtido quando o compósito alcança alto valor de conversão até o ponto de vitrificação. O P90 mostrou comportamento semelhante aos compósitos baseados em dimetacrilatos quanto à cinética de polimerização, inclusive sob variação de irradiância e temperatura. De uma maneira geral, a umidade não exerceu grande influência na cinética de polimerização do P90 e do EHD. Como não se sabe a composição exata do Filtek P90, pode-se dizer apenas que a conversão deste material é cerca de 40 %. O teste de titulação precisa ser aperfeiçoado e são necessários estudos adicionais para se validar a metodologia FTIR X titulação utilizada. Como a composição monomérica exata do Filtek P90 não é conhecida, não foi possível precisar a conversão deste material com os métodos empregados, porém pode-se dizer que este material apresenta, no mínimo, cerca de 40 % de conversão, dada pela banda em 4156 cm-1. / OBJECTIVE: To characterize the interaction between polymerization kinetics and stress and its determining parameters, and evaluate polymer network quality and mechanical properties of commercial composites for posterior teeth based on dimethacrylate or silorane. Also, the influence of the intensity of the light source, temperature and humidity on the polymerization reaction was evaluated. Finally, the degree of conversion (DC) of the composite based on silorane was evaluated by spectroscopy and titration. METHODS: three \"low shrinkage\" composites were chosen: Kalore (KAL - GC America) and N\'Durance (NDUR - Septodont), based on dimethacrylates, and Filtek P90 (P90 - 3MESPE), based on silorane. EsthetX HD (EHD - Dentsply) was used as a control. Polymerization stress (PS) of samples (n = 5, Ø = 5 mm; h = 1 mm, 10 min) was obtained using a universal testing machine. Volumetric shrinkage (VS) was determined in a linometer (n = 3, Ø = 6 mm, h = 1.5 mm, 10 min). Elastic modulus (E) and flexural strength (FS) (n = 10; 10 x 2 x 1 mm) were obtained by three point bending test (8 mm between support, 0.5 mm/min). DC and polymerization rate (Rp) of specimen (n = 3, Ø = 6.5 mm, h = 0.8 mm) were determined by NIR spectroscopy (peak 6165 cm-1 for dimethacrylates and 4156 cm-1 and 4071 cm-1 for silorane). For these tests, photopolymerization was performed with 740 mW/cm2 x 27 s (Bluephase G2 - Ivoclar). Glass transition temperature (Tg), loss tangent (LT), degree of heterogeneity and crosslink density of specimens (n = 3, 15 x 3 x 1 mm) with maximum conversion was obtained in a dynamic mechanical analyzer. Analysis of extracts obtained after specimen immersion (Ø = 12 mm, h = 0.8 mm; 970 mW/cm2 x 30 s) in dichloromethane was carried out using 1H-NMR to determine residual monomers. Polymerization kinetics of specimens (n = 3; Ø = 5.5 mm, h = 1 mm) of all materials cured with Acticure 4000 - EXFO and 320-500 nm filter, was analyzed using different levels of irradiance (3, 30 or 200 mW/cm2) and temperature (23, 35 or 60 °C) by NIR spectroscopy (peak 6165 cm-1 for dimethacrylates and 4156 cm-1 for silorane). The influence of moisture at 23, 35 or 60 °C on polymerization kinetics was observed for Filtek P90 and EsthetX HD. To assist in the identification of peaks that can be used to calculate the conversion of Filtek P90, peaks related to epoxy rings selected with the spectroscopic characterization (Mid-IR and NIR) of model monomers and Filtek P90 (after filler extraction with acetone) were compared with the values found in acid-base titration test of these materials. Data were submitted to ANOVA and Tukey\'s test ( < 0.05). RESULTS: EHD showed the greatest TP, statistically similar to NDUR and greater than KAL and P90, statistically similar. EHD Cvol was superior to NDUR, and P90 and KAL had the lowest and statistically similar values. P90 had the highest MeFLex, with no difference between other materials. EHD had the highest RFlex value, and NDUR and KAL, the lowest one, with no difference between them. NDUR had the highest DC, followed by EHD and KAL, and P90 had the lowest value. EHD showed the highest Tg, followed by P90 and KAL and NDUR. NDUR and P90 showed respectively the highest and lowest LT. NDUR and KAL had the highest and the lowest homogeneity, respectively. P90 had the highest crosslink density, with no difference between other composites. Unlike EHD and KAL, NUR and P90 showed no leachable monomers. P90 showed similar polymerization kinetics to dimethacrylate composites, even with irradiation and temperature variation. Moisture slightly increased the DC of EHD at 23 and 35 °C, and temperature showed greater influence at 60 °C. In general, moisture did not influence P90 polymerization kinetics. P90 showed 60 % conversion in Mid-IR over the peak 883 cm-1, similar to the value obtained with titration. Two distinct peaks showed conversion in NIR: 4156 cm-1 (42 %) and 4071 cm-1 (65 %). CONCLUSION: DC had a great influence on PS values. Higher E and FS values were associated with higher crosslink density. NDUR and P90 showed no leachable monomers. A higher DC is obtained when the composite reaches high values of conversion before vitrification. P90 showed similar behavior to composites based on dimethacrylate regarding the polymerization kinetics, including under variation of irradiance and temperature. In general, moisture does not great influence P90 and EHD polymerization kinetics. As the exact composition of P90 is unknown, it was not possible to specify the conversion of this material with the methods employed, but it can be said that this material exhibits at least about 40 % conversion, provided by the peak 4156 cm-1.

Este estudo teve como objetivo investigar múltiplos aspectos relacionados a polimerização da resina composta como: o grau de conversão monomérica (GC), parâmetros da cinética de polimerização e a determinação de monômeros residuais TEGDMA e BisGMA, além de avaliar o desempenho de aparelhos fotoativadores. As resinas compostas experimentais foram manipuladas variando-se os fotoiniciadores R1-) canforoquinona/amina, R2-) PPD/amina, R3-) PPD + canforoquinona/amina) e foram utilizados dois aparelhos para a fotoativação (I-) lâmpada halógena (Demetron LC/ SDS Kerr-USA) e II-) LED (Poly 600/Kavo-Brasil) ambos com 600 mW cm-2, por 40 s. O GC após 300 s e os parâmetros de cinética como taxa máxima de conversão (Rpmáx), tempo em que ocorreu a taxa máxima de polimerização (tmáx) e a conversão quando ocorreu a Rpmáx, foram determinados por meio de espectroscopia de absorção no infravermelho em tempo real (RT-FTIR), Os espectros foram coletados dos espécimes (n=5) no modo cinética, durante 305 s, entre 1680 e 1550 cm-1. As 5 primeiras varreduras coletadas serviram para fornecer o espectro de absorção da resina não polimerizada (utilizado no cálculo do GC). Na 6&ordm; varredura, o fotoativador foi ligado (por 40 segundos) enquanto o espectro continuava a ser coletado até 300 s após a ativação da luz. A presença de monômeros residuais (TEGDMA e BisGMA) foi avaliada por meio da cromatografia líquida de alta eficiência (HPLC), sendo que os espécimes (n=6) foram imersos em acetonitrila (5 mL-24 h) com agitação mecânica, o método desenvolvido utilizou: HPLC, coluna C18, fase móvel A: água com trietilamina (0,05%) acidificada com ácido acético (pH 4) e B: acetonitrila, modo de eluição com gradiente (40-85%-17 min/ 55&deg;C), fluxo de 1 mL min-1, detector UV em 210 nm, injeção de 20 &micro;L. Em relação aos resultados de GC após 300 s os maiores valores foram para a resina R1 tanto fotoativada com LED (65,90% &plusmn;1,81) quanto com a lâmpada halógena (64,40% &plusmn;0,83), e os menores valores encontrados foram quando a resina R2 foi fotoativada pelo LED (35,64% &plusmn;1,73) e a única resina que apresentou diferenças significantes em relação as fontes de luz foi a R2. Os valores da Rpmáx diminuíram nas resinas que apresentavam o fotoiniciador PPD. O tempo de ocorrência da taxa máxima de conversão (tmáx) aconteceu mais rapidamente para a resina com CQ. Todas as resinas apresentaram valores de grau de conversão similares no tmáx. Em relação aos resultados de HPLC, a quantidade de monômeros extraídos (M/M%) variou de 1,98% &plusmn;0,16 à 3,34% &plusmn;0,07 para os monômeros TEGDMA e de 3,57% &plusmn;0,30 à 7,57% &plusmn;0,40 para os monômeros BisGMA. A resina R2 apresentou a maior quantidade de monômeros residuais quando fotoativada com ambas as fontes, principalmente quando fotoativada com o LED. As resinas R1 e R3 obtiveram comportamento parecidos para ambos fotoativadores. Conclui-se que a resina R3 pode ser uma boa opção, pois quando comparada com a resina R1 apresentou vantagens como: redução na Rpmáx, bem como o momento em que esta ocorreu (tmáx), além de ser adequadamente fotoativada com aparelhos de LED. / This study aimed to investigate multiple aspects of composite resin polymerization as the degree of monomer conversion (DC), the kinetic parameters of polymerization and the determination of residual monomers TEGDMA and BisGMA, and evaluate the performance of light curing units. The experimental composites were manipulated by varying the photoinitiators R1-) camphorquinone/amine, R2-) PPD/amine, R3-) PPD + camphorquinone/ amine) and two devices were used for the polymerization I-) halogen lamp (Demetron LC / SDS Kerr, USA) and II-) LED (Poly 600/Kavo-Brasil) both with 600 mW cm-2 for 40 s. DC after 300 s and the kinetic parameters such as maximum rate of polymerization conversion (Rpmax), time of occurrence of the maximum rate of polymerisation (tmax) and the conversion occurred when Rpmax were determined by infrared absorption spectroscopy in real time (RT-FTIR), the infrared spectrum was collected from the specimen (n=5) in order kinetics for 305 s, between 1680 and 1550 cm-1. The first 5 scans were used to provide the collected absorption spectrum of the uncured resin (calculated DC). In the sixth scan, the curing unit was connected (by 40 seconds) while the spectrum continued to be collected up to 300 s after activation of the light. The presence of residual monomers (TEGDMA and BisGMA) was assessed by high performance liquid chromatography (HPLC), and the specimens (n=6) were immersed in acetonitrile (5 mL-24 h) with mechanical stirring, the method developed used: HPLC, C18 column, mobile phase A: water with triethylamine (0,05%) acidified with acetic acid (pH 4) and phase B: acetonitrile, gradient elution mode (40-85% -17 min/55 &deg;C), flow 1 mL/min, UV detector at 210 nm, injection of 20 &micro;L. Regarding the results of DC after 300s were the highest values for both R1 resin polymerized with LED (65.90% &plusmn;1.81) and with a halogen lamp (64.40% &plusmn;0.83), and lower values when the resin was found that R2 was polymerized by LED (35.64% &plusmn;1.73) and the only resin that showed significant differences in the sources of light was the R2. The values of the resins decreased Rpmax who had PPD photoinitiator. The time of occurrence of the maximum rate of conversion (tmax) occurred more rapidly for the resin with CQ. And all resins showed values similar degree of conversion in tmax. For HPLC results, the amount of monomer extracted (M/M%) ranged from 1.98% &plusmn;0.16 to 3.34% &plusmn;0.07 for the monomers of TEGDMA and 3.57% &plusmn;0.30 to 7.57% &plusmn;0.40 for the monomers BisGMA. Resin R2 showed the highest amount of residual monomers as polymerized with both sources, especially when polymerized with LED. Resins R1 and R3 had similar behavior for both curing units. In conclusion, the resin R3 can be a good choice, as compared with the resin obtained R1 advantages as reduction in Rpmax as well as the time it occurred (tmax), and be suitably photoactivated with LED devices.

Microfluidic devices have long been considered an ideal tool for rapid and inexpensive chemical analysis and reactions in areas ranging from point-of-care health to national security applications. However, fabricating microfluidic devices is time consuming, difficult and above all expensive. In commercial applications many thousand units need to be sold before the development costs are recovered. The problem is compounded since most microfluidic devices do not have generalized architectures which means that each end use requires a specialized design. The microfluidics marketplace can therefore be seen as being composed of 1000’s of niche markets. To address development costs, there is clearly a need for a versatile technology that can be used for many different applications and that enables rapid testing and optimization of new designs. This work describes such a technology: Contact Liquid Photolithographic Polymerization (CLiPP). The thesis consists of two parts: polymerization kinetics and the fabrication of polymeric microfluidic devices via CLiPP. The photopolymerization kinetics is evaluated for a number of monomer types, and the results are used to assess their suitability in the CLiPP process. Vinyl ether/maleate photoinitiated copolymerization is examined in detail. It is shown that the polymerization kinetics is dramatically influenced by the availability of easily abstractable hydrogens The presence of α-hydrogens adjacent to the vinyl ether functional group reduces the polymerization rate and the dependence of the polymerization rate as a function of initiation rate. Also, photoinitiated acrylate and methacrylate polymerization kinetics are presented. The kinetics results in these three monomer types are used to explain the different patterning properties of the monomer functionalities used in the CLiPP process, in which acrylates show enhanced patterning properties compared to methacrylates. The polymerization kinetics is studied with traditional tools and methods: photo Differential Scanning Calorimetry (photo-DSC), photo Fourier Transform Real Time Infrared Spectroscopy (photo-RTIR), and photo Real Time Electron Paramagnetic Spectroscopy (ESR). The microfluidic fabrication is performed via both in-house fabricated and commercially available CLiPP-specific hardware. The patterning qualities of the structures are evaluated via Scanning Electron Microscopy (SEM) and Optical Microscopy. The finished devices are used in their intended environment and evaluated in suitable manners to assess their utility. In this thesis, the development and design of specialized CLiPP fabrication machines, fabrication techniques and resulting microfluidic device features are presented anddiscussed. It is shown that the CLiPP scheme enables features such as 3 dimensional (3D) capabilities for minimized device footprints, a very large number of polymeric materials for optimized device components as well as facile integration of prefabricated components. Also, covalent layer adhesion and permanent surface modifications via living radical processes are demonstrated. These capabilities are exemplified in a number of examples that range from a 3D fluidic channel maze with separated fluidic streams and a device with independently moveable parts to a device constructed from multiple polymeric materials and devices with permanently modified surfaces, Also, batch processing capabilities are shown through fabrication of 400 identical undercut microstructures. Rapid and inexpensive design evaluations, multiple materials capabilities and the ability to seamlessly incorporate prefabricated microstructures of the CLiPP process strongly encourages continued method development. The future work that remains to be addressed is divided into two parts. First, to enable novel research devices, new polymer materials with enhanced mechanical and surface properties must be developed. Also, integration of prefabricated microstructures such as sensors and actuators has to be incorporated in a reproducible and rational manner. Secondly, to enable device mass fabrication, new automated equipment is to be developed in order to utilize the full batch processing potential of CLiPP. / QC 20101019

<p>Microfluidic devices have long been considered an ideal tool for rapid and inexpensive chemical analysis and reactions in areas ranging from point-of-care health to national security applications. However, fabricating microfluidic devices is time consuming, difficult and above all expensive. In commercial applications many thousand units need to be sold before the development costs are recovered. The problem is compounded since most microfluidic devices do not have generalized architectures which means that each end use requires a specialized design. The microfluidics marketplace can therefore be seen as being composed of 1000’s of niche markets.</p><p>To address development costs, there is clearly a need for a versatile technology that can be used for many different applications and that enables rapid testing and optimization of new designs. This work describes such a technology: Contact Liquid Photolithographic Polymerization (CLiPP).</p><p>The thesis consists of two parts: polymerization kinetics and the fabrication of polymeric microfluidic devices via CLiPP.</p><p>The photopolymerization kinetics is evaluated for a number of monomer types, and the results are used to assess their suitability in the CLiPP process. Vinyl ether/maleate photoinitiated copolymerization is examined in detail. It is shown that the polymerization kinetics is dramatically influenced by the availability of easily abstractable hydrogens The presence of α-hydrogens adjacent to the vinyl ether functional group reduces the polymerization rate and the dependence of the polymerization rate as a function of initiation rate. Also, photoinitiated acrylate and methacrylate polymerization kinetics are presented. The kinetics results in these three monomer types are used to explain the different patterning properties of the monomer functionalities used in the CLiPP process, in which acrylates show enhanced patterning properties compared to methacrylates. The polymerization kinetics is studied with traditional tools and methods: photo Differential Scanning Calorimetry (photo-DSC), photo Fourier Transform Real Time Infrared Spectroscopy (photo-RTIR), and photo Real Time Electron Paramagnetic Spectroscopy (ESR).</p><p>The microfluidic fabrication is performed via both in-house fabricated and commercially available CLiPP-specific hardware. The patterning qualities of the structures are evaluated via Scanning Electron Microscopy (SEM) and Optical Microscopy. The finished devices are used in their intended environment and evaluated in suitable manners to assess their utility.</p><p>In this thesis, the development and design of specialized CLiPP fabrication machines, fabrication techniques and resulting microfluidic device features are presented anddiscussed. It is shown that the CLiPP scheme enables features such as 3 dimensional (3D) capabilities for minimized device footprints, a very large number of polymeric materials for optimized device components as well as facile integration of prefabricated components. Also, covalent layer adhesion and permanent surface modifications via living radical processes are demonstrated. These capabilities are exemplified in a number of examples that range from a 3D fluidic channel maze with separated fluidic streams and a device with independently moveable parts to a device constructed from multiple polymeric materials and devices with permanently modified surfaces, Also, batch processing capabilities are shown through fabrication of 400 identical undercut microstructures.</p><p>Rapid and inexpensive design evaluations, multiple materials capabilities and the ability to seamlessly incorporate prefabricated microstructures of the CLiPP process strongly encourages continued method development. The future work that remains to be addressed is divided into two parts. First, to enable novel research devices, new polymer materials with enhanced mechanical and surface properties must be developed. Also, integration of prefabricated microstructures such as sensors and actuators has to be incorporated in a reproducible and rational manner. Secondly, to enable device mass fabrication, new automated equipment is to be developed in order to utilize the full batch processing potential of CLiPP.</p>