Biodegradable hydrogels have become very promising materials for a number of biomedical applications, including tissue engineering and drug delivery. For optimal tissue engineering design, the mechanical properties of hydrogels should match those of native tissues as closely as possible because these properties are known to affect the behavior and function of cells seeded in the hydrogels. At the same time, high water-contents, large mesh sizes and well-tuned degradation rates are favorable for the controlled release of growth factors and for adequate transport of nutrients through the hydrogel during tissue regeneration. With these factors in mind, the goal of this research was to develop and investigate the behavior of injectable, biodegradable hydrogels with enhanced stiffness properties that persist even at high degrees of swelling. In order to do this, degradable functionalities were incorporated into photo-crosslinkable poly(ethylene glycol) and poly(acrylic acid) hydrogels, and these two components were used to make a series of double-network hydrogels. Synthesis of the precursor macromers, photopolymerization of the hydrogels, and structural parameters of the hydrogels were analyzed. The composition and the molecular weight between crosslinks (Mc) of the hydrogel components were varied, and the degradation, swelling, thermal and mechanical properties of the hydrogels were characterized over various time scales. These properties were compared to corresponding properties of the component single-network hydrogels.

This work deals with the fabrication process of low density foam shells and the sharp control of their shape (diameter, thickness, density, sphericity, non-concentricity). During this PhD we focused on the non-concentricity criterion which has to be lower than 1%. The shells are synthesized using a microencapsulation process leading to a double emulsion and followed by a thermal polymerization at 60°C. According to the literature, three major parameters, the density of the three phases, the deformations of the shells along the process and the kinetics of the polymerization have a direct influence on the shells non-concentricity. The results obtained showed that when the density gap between the internal water phase and the organic phase increases, the TMPTMA shells non-concentricity improves. A density gap of 0.078 g.cm-3 at 60°C, leads to an average non-concentricity of 2.4% with a yield of shells of 58%. It was also shown that the synthesis process can be considered as reproducible. While using the same internal water phase, equivalent non-concentricity results are obtained using either a straight tube, a tube with areas of constriction or a short wound tube. The time required to fix the shell's shape is at least 20 minutes with thermal polymerization. So, it seems that the time spent by the shells inside the rotating flask allows the centering of the internal water phase inside the organic phase, whatever the circulation process used. In order to get higher polymerization rates and to avoid destabilization phenomena, we then focused our study on photopolymerization. When the synthesis is performed using a UV lamp with an efficient light intensity, the shells have a slightly higher thickness than the shells synthesized by thermal polymerization. Moreover, a really higher yield, around 80%, is achieved with UV polymerization. However, the average non-concentricity of the shells synthesized lays around 20%, which is really high compared to the 2.4% average non-concentricity obtained with thermal polymerization. It would be interesting to expose the shells to UV light at different times after collection in order to study the influence of the agitation time on the shells non-concentricity.

N-methyl-6-hydroxyquinolinium (NM6HQ) is a powerful excited-state proton donor, exhibiting a huge pKa drop from 7.2 in the ground state to -7 in the excited state. The zwitterionic nature of the proton transfer product encourages intramolecular electron transfer away from the hydroxyl moiety to the distal ring, allowing for a large pKa jump in the excited state. This process is reversible, making the NM6HQ salts powerful transient superacids. We have investigated the excited-state proton transfer (ESPT) from NM6HQ salts to various basic solvents (alcohols, DMSO). A model has been developed that adequately describes the ion-dipole interactions in the ESPT geminate-recombination process. Our studies have shown that the counterion plays a large role in the ESPT. Likewise, initiation of cationic polymerization is controlled by the counterion. NM6HQ perfluoroalkylsulfonates appear to be the first molecules reported which are capable of initiating aliphatic epoxide polymerization at room temperature through a proton transfer mechanism.

O objetivo do trabalho foi sintetizar e caracterizar nanopartículas de poliestireno e polimetacrilato de metila com morfologia núcleo-casca obtidas através da polimerização em emulsão sem emulsificante em dois estágios e através da fotopolimerização. Nos experimentos avaliou-se a influência de diferentes condições operacionais baseadas em fatores cinéticos sobre os dois estágios da polimerização. As condições avaliadas para o primeiro estágio de preparação de núcleos foram: a temperatura do processo, a concentração de iniciador e de monômero, e o efeito de agentes modificadores de superfície (sal, co-monômero e reticulante). Para o segundo estágio de formação da casca as condições avaliadas foram: a concentração e o regime de alimentação de monômero. Os resultados experimentais mostraram que uma relação de co-monômero e reticulante é a melhor alternativa para preparar núcleos estáveis e de diâmetros pequenos. Assim, o revestimento uniforme dos núcleos é obtido no segundo estágio e com isso a morfologia núcleo-casca em equilíbrio é alcançada. Dois sistemas experimentais (reator convencional e reator fotoquímico) foram propostos e avaliados na sua eficiência para obter partículas com este tipo de morfologia no segundo estágio (formação do revestimento). As diversas técnicas de caracterização indicaram a formação de morfologia núcleo-casca na maioria dos casos estudados para os dois sistemas propostos. Por sua vez, as técnicas espectroscópicas (NIR e Raman) permitiram o monitoramento do processo em tempo real e a elaboração de modelos de calibração que correlacionaram o crescimento do tamanho da partícula núcleo. Da mesma forma, os fatores termodinâmicos foram estudados para predizer a morfologia final esperada nos sistemas. Os resultados, experimental e predito são comparados e discutidos em termos de aspectos chave envolvidos no controle da morfologia da partícula. / This work aimed at studying the synthesis and characterization of core-shell nanoparticles of polystyrene and polymethylmethacrylate obtained in a two-stage emulsifier-free emulsion polymerization and photopolymerization. The influence of different operational conditions based on kinetic factors was experimentally evaluated. In the first stage (seed preparation) the process temperature, initiator and monomer concentrations and the effect of surface-modifier agents (acids, salts, co-monomers and crosslinker) were investigated; similarly in the second stage, the concentration and feeding regime of monomer were evaluated with respect to the shell formation. Experimental results showed that both, crosslinker and co-monomer are the best alternative to achieve a stable seed with small diameter; hence, with this core, uniform coating is obtained in the second stage and core-shell morphology is reached. In order to evaluate the efficiency of the preparation of core-shell particles, two experimental systems (conventional and photochemical reactor) were studied. Different characterization techniques indicated that in most of the cases studied particles with the desired core-shell morphology were formed. The use of spectroscopic techniques NIR and Raman were tested for the real-time monitoring of the process using adequate calibration models developed to correlate the average size of the growing core particle with the spectra. In the same way, thermodynamic factors were used to predict the expected final morphology of the particles. Experimental and predicted results were compared and discussed in terms of the key aspects involved in the control of the particle morphology.

Orientador: Mario Alexandre Coelho Sinhoreti / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-08-08T10:42:08Z (GMT). No. of bitstreams: 1 Alonso_RobertaCarolineBruschi_D.pdf: 2828251 bytes, checksum: 644a34bfa8b27efb0da35a9b5d7f13de (MD5) Previous issue date: 2007 / Resumo: A formação de fendas em restaurações de compósito foi caracterizada neste estudo, abrangendo-se técnicas de avaliação, fatores modificadores e a relação com a resistência de união das restaurações à estrutura dental. No capítulo 1, objetivou-se validar a técnica do corante para avaliação das fendas através da comparação com a observação em Microscopia Eletrõnica de Varredura (MEV). Vinte incisivos bovinos foram selecionados e desgastados até expor uma área plana em dentina, onde duas cavidades foram preparadas e restauradas com o compósito Filtek 2250 ou Filtek Flow. As amostras foram polidas e réplicas foram obtidas em resina epóxica. As réplicas foram observadas em MEV para determinar a porcentagem de fenda ao longo da margem cavitária. Na técnica do corante, Caries Detector (Kuraray) foi aplicado sobre as restaurações durante 5s. A imagem digital das restaurações coradas foi analisada com o software Image Tool para determinar a porcentagem de fendas. Os dados foram submetidos a ANOVA e teste de correlação de Pearson. Filtek Flow apresentou 35,54% e 33,52%, e Filtek 2250 26,68% e 29,11% de fendas, quando avaliadas em MEV e pela técnica do corante, respectivamente. Não houve diferença significativa entre os compósitos independente do método de avaliação, havendo forte correlação positiva (r=0,83) entre eles. Concluiu-se que a técnica do corante pode ser utilizada para avaliação das fendas com confiabilidade dos resultados. No capítulo 2, o efeito de métodos de fotoativação modulados na' adaptação marginal e intema de restaurações confeccionadas com diferentes compósitos foi determinado. Sessenta terceiros molares foram selecionados, seccionados (2 fragmentos) e tiveram a superfície vestibular ou palatina ou lingual desgastada para expor uma área plana em esmalte, onde uma cavidade foi confeccionada. Os dentes foram distribuídos em 12 grupos (n=lO), segundo o compósito restaurador (Filtek 2250, Herculite XRV e Heliomolar) e o método de foto ativação (Luz continua; Soft-Start; Pulse delay; Luz intermitente). O teste de adaptação marginal (técnica do corante) foi conduzido da mesma maneira descrita anterionnente. Após, os espécimes foram seccionados dividindo a restauração em 4 fatias, que foram coradas e o mesmo procedimento de avaliação da adaptação marginal foi realizado para determinar a adaptação intema. Assim, põde-se observar que todas as restaurações apresentaram perfeito selamento das margens extemas. Considerando as fendas intemas, os métodos modulados geraram redução significativa nas fendas quando comparados à luz contínua, independe do compósito empregado. Filtek 2250 apresentou a melhor adaptação interna, independente do método de fotoativação. A interação tipo de compósito e método de fotoativação não foi significativa. Conclui-se que os métodos de fotoativação modulados são eficientes na redução da formação de fendas internas e que podem ser indicados para a prática clínica, independente do compósito empregado. No capítulo 3, o objetivo foi relacionar a resistência da união à adaptação marginal e interna de restaurações fotoativadas por diferentes métodos. A resistência da união foi mensurada em cavidades tronco-conicas confeccionadas em dentes bovinos através do teste push-out (Instron). A adaptação marginal e interna das restaurações foi verificada da mesma maneira descrita anteriormente. Em ambos os testes, as cavidades foram restauradas com o compósito Esthet-X, sendo as amostras distribuídas em 5 grupos (n=10), de acordo com o método de fotoativação: G 1 - Luz contínua; G2 - Luz contínua baixa intensipade; G3 - Soft-start; G4 - Luz Intermitente; G5 - Pulse Delay. A dose de energia foi padronizada em 14J. Os dados foram submetidos a ANOVA e teste de Tukey. Considerando resistência da únião, G5 (7,2 MPa) apresentou resultados significativamente melhores que G 1 (4,6 MPa). G2, G3 e G4 tiveram médias intermediárias, não havendo diferenças significativas entre esses grupos e entre eles e G 1 ou G5. Considerando adaptação marginal, não houve diferença significativa entre os grupos. Na adaptação interna (que incluía o substrato dentinário), o resultado foi inverso ao do teste de resistência de união, ou seja, G5 (2,8%) teve menor média de fendas que G 1 (10,1%). Concluiu-se que a modulação da energia luminosa pode acarretar em aumento da resistência da união e redução na formação de fendas internas, havendo relação inversa entre resistência da união e formação de fendas internas / Abstract: Gap formation in composite restorations has been characterized in this dissertation by way of evaluation techniques, modifying factors and the relationship between bond strength of the restorations and the dental structure. In Chapter 1 the objective was to compare the dye staining technique to Scanning Electron Microscopy (SEM) evaluation of gap formation in order to validate the dye technique. Twenty bovine incisors were selected and ground so as to expose a flat dentin area in which two circular cavities were prepared and restored using Filtek 2250 or Filtek Flow. The specimens were polished and replicas were obtained in epoxy resin. Replicas were observed in SEM to determine the percentage of gap fonnation in the margins of the restorations. In dye staining technique, the Caries Detector was applied on each restoration for 5 seconds. Digital images of the stained restorations were analyzed using Image Tool to determine gap percentage. Data were submitted to ANOVA and Pearson's correlation. Filtek Flow showed 35.54% and 33.52% of gap and Filtek 2250 showed 26.68% and 29.11%, when evaluated using SEM and Dye staining technique, respectively. There was no difference between the composites, regardless of the evaluation technique. There was a strong positive correlation (r=0.83) between the results obtained through the tested methods to assess marginal gap. This led to the conclusion that dye staining technique can be reliably employed to evaluate the gap fonnation in composite restorations. Chapter 2 aims at determining the effect of modulated photoactivation methods on gap fonnation of restorations using different composites. Sixty third molars were selected, sectioned (2 fragments) and ground so as to expose a flat enamel area in which a cavity was prepared. The specimens were distributed into twelve groups (n=10), according to the restorative composite (Filtek 2250, Herculite XRV, and Heliomolar) and the photoactivation method (Continuous Light, Soft-Start, Pulse Delay, and Intermittent Light) applied. Marginal adaptation test was conducted in the same way described before (dye staining technique). The specimens were then sectioned in 4 slices, all of which were stained, and the same evaluation procedure used to determine marginal adaptation was employed to evaluate internal gap fonnation. All restorations showed perfect sealing of the enamel outer margins. With regards to internal adaptation, modulated photoactivation methods showed a significant reduction on gap fonnation when compared under continuous light, regardless of the composite. Filtek 2250 showed the best internal adaptation, regardless of the photoactivation method. The interaction between restorative composite and photoactivation method was not significant. The conclusion was that modulated photoactivation methods decrease the internal gap formation of composite restorations and should thus be encouraged on clínical practice, regardless of the type of composite. In Chapter 3, the aim was to evaluate the relationship between bond strength and marginal and internal adaptation of composite restorations photocured by different methods. Bond strength was measured in conical cavities prepared in bovine incisors using push-out test (Instron). Marginal and internal adaptation testswere conducted in the same way as before (dye staining technique). For both tests, cavities were filled with Esthet X resin composite. The specimens were distributed into 5 groups (n= 1 O) according to photoactivation method: G 1 - continuous light; G2 low intensity continuous light; G3 - soft start; G4 - intermittent light; G5 - pulse delay. 14J was the standard energy dose. Data were submitted to ANOVA and Tukey's test. Regarding bond strength, G5 (7.2 MPa) was statistically superior to Gl (4.6 MPa). G2, G3 and G4 showed intermediate mean values, which were not different from each other or from G 1 or G5. Regarding marginal adaptation, there was no statistical difference among the groups. Internal adaptation results (that included dentin substrate) were the opposite of bond strength results. G5 (2.8%) showed a reduction on gap formation when compared to Gl (10.1%). In conclusion, it may be said that the modulated photocuring methods can increase bond strength while decreasing internal gap formation. An opposite relationship was observed regarding push-out bond strength and internal adaptation of composite restorations / Doutorado / Materiais Dentarios / Doutor em Materiais Dentários

Os revestimentos curáveis por radiação ultravioleta (UV) ou feixe de elétrons (EB) são sistemas líquidos reativos compostos por resinas, diluentes (monômero) e aditivos, capazes de formar compostos poliméricos termorrígidos por reações de polimerização e reticulação induzidas por radiação. Esta tecnologia tem sido empregada como alternativa aos processos convencionais no desenvolvimento de uma variada gama de produtos. Um dos grandes desafios da aplicação da tecnologia de cura UV/EB em produtos a serem submetidos ao intemperismo é a manutenção de suas propriedades físicas e de sua aparência. Este trabalho apresenta informações sobre o comportamento de quatro vernizes com e sem aditivos estabilizantes à luz-curados por radiação UV ou EB quando submetidos ao processo de envelhecimento acelerado. Os vernizes foram caracterizados por técnicas termoanalíticas como termogravimetria (TG), calorimetria exploratória diferencial (DSC) e fotocalorimetria diferencial (foto-DSC); espectroscopia de absorção no infravermelho e no ultravioleta, e propriedades mecânicas. Os vernizes sob a forma de filmes de 50 µm de espessura foram curados com diferentes doses de radiação UV ou EB. A cura por radiação UV foi conduzida em túnel de luz, provido de uma lâmpada de mercúrio de média pressão e esteira rolante com velocidade variável. As diferentes doses de radiação UV de 50 a 1500 mJ cm-2 foram obtidas variando-se a velocidade da esteira. A cura por EB foi realizada utilizando-se acelerador de elétrons de energia de 1,5 MeV, sob atmosfera de nitrogênio, aplicando-se doses no intervalo de 1,6 a 300 kGy. O grau de cura dos diferentes filmes foi calculado por meio dos valores das entalpias de reação da cura residual obtidos por DSC. Os testes de envelhecimento acelerado dos filmes curados foram feitos em câmara de envelhecimento do tipo Weather-Ometer por períodos de exposição de 100 a 3000 horas. Os dados obtidos experimentalmente foram avaliados em função da composição dos vernizes, da dose e do tipo de radiação empregada na cura e do tempo de permanência na câmara de envelhecimento. Os resultados indicam que os filmes curados por EB apresentam maior durabilidade frente ao intemperismo do que os seus pares curados por radiação UV. Os filmes não estabilizados (sem aditivos) apresentam grande instabilidade nas condições do teste de envelhecimento. O efeito do envelhecimento foi observado por meio de dados de dureza, brilho, rugosidade, índice de amarelecimento e alteração das bandas de absorção dos espectros FTIR. / The materials curable by ultraviolet (UV) or electron beam (EB) radiation such as inks, adhesives and coatings are reactive compounds made up of resin, monomer, photoinitiator and additives which undergo polymerization and crosslinking under irradiation producing thermoset products. This technology has been used in a great variety of industrial applications, replacing the conventional curing process in the development of new products. One of the challenging applications has been to design weatherable radiation cured coating which maintain their desirable physical properties and aesthetic appearance. This research reports information about the behavior of four UV and EB curable clear coatings -with or without light stabilizer additives- under accelerated weathering. Thermogravinietry, differential scanning calorimetry, differential photocalorimetry, infrared and ultraviolet spectroscopy and tensile properties were used to evaluate these formulations. Clear coating 50 µm thick films were cured with UV and EB radiation at different doses. The UV curing process was carried out at room temperature using an UV tunnel, with a medium pressure mercury lamp and a transport belt with variable speed. The ultraviolet radiation doses were in the range of 50 to 1500 mJ cm-2. The EB curing process was performed under N2 atmosphere, with doses in the range from 1,6 to 300 kGy using the IPEN-CNEN/SP Dynamitron electron beam accelerator with energy of 1.5 MeV. The cure degree was determined by means of the residual reaction heat of the undercured samples obtained from photo-DSC or DSC measurements. The accelerated aging tests were carried out using a Weather-Ometer chamber with exposition times in the range of 100 to 3000 hours. The experimental data obtained from the photo-aged samples were evaluated and correlated to the formulation composition, type of radiation - UV or EB, radiation dose and residence time in the aging chamber. The results have shown that the EB cured films have a better resistance to photoinduced weathering effects than UV cured ones. UV/EB films with light stabilizers have shown larger stability than those counterparts with no additives. The aging effects were evaluated by parameters such as hardness, gloss, surface roughness, yellowness index and changes in the FTIR absorption bands.

O objetivo do trabalho foi investigar múltiplos aspectos relacionados ao pré-aquecimento da resina composta anterior à fotoativação: o grau de conversão e a cinética da polimerização em função da temperatura de polimerização, tempo de fotoativação e profundidade; o desempenho da fonte aquecedora (temperatura máxima, estabilidade térmica do aparelho e variações de temperatura ao pré-aquecer compules) e aspectos clínicos (o efeito de ciclos de pré-aquecimento repetidos e prolongados sobre o grau de conversão, a variação da temperatura intrapulpar in vitro e a variação da temperatura in vivo ao usar resina composta pré-aquecida ou a temperatura ambiente. A conversão de monômeros e os parâmetros de cinética foram determinados através de FTIR-ATR. Os espécimes foram fotoativados por 5, 10, 20 ou 40s entre 3 o e 60 o C. Foram calculados o grau de conversão em tempo real, a taxa máxima de conversão, o tempo em que ocorreu a taxa máxima, e a conversão na taxa máxima. Os dados foram tratados por análise de variância, teste-t e análise de regressão (p ≤0,05). O desempenho do dispositivo aquecedor foi medido monitorando-se a mudança de temperatura em tempo real com o auxílio de um termopar tipo-k conectado a um conversor analógico-digital. Os termopares foram colocados no aquecedor e dentro de compules de compósito. Os dados foram analisados com teste t (p ≤0,05). Compules (n=5) foram submetidos a um dos ciclos térmicos: Pré-aquecimento repetido (da temperatura ambiente a 60 o C, por 10 vezes) ou Prolongado (24h a 60 o C). O grau de conversão foi medido 24h após os ciclos, com o compósito à temperatura ambiente, seguindo o protocolo descrito acima. Os dados foram tratados por análise de variância e teste de Tukey (p≤0,05). O aumento da temperatura intrapulpar foi medido por um termopar colocado na câmara pulpar de um prémolar contendo uma cavidade de Classe V (com 1mm de espessura de dentina remanescente). O preparo foi preenchido com compósito à temperatura ambiente ou pré-aquecido enquanto a temperatura intrapulpar era continuamente monitorada (n=5). Os dados foram comparados por análise de variância e teste de Tukey (p ≤0,05). Para a medida da variação de temperatura in vivo, foram feitos preparos cavitários de 2mm de profundidade em dentes posteriores de um indivíduo (n=3). Uma sonda que mensurava a temperatura foi introduzida no dente preparado em cada procedimento restaurador e durante a inserção da resina composta à temperatura ambiente ou pré-aquecida a 60°C. Os dados foram comparados com análise de variância e teste de Tukey (p ≤0,05). Os resultados indicaram que: 1) o pré-aquecimento da resina composta anterior à fotoativação aumenta o grau de conversão, reduz o tempo de fotoativação e resulta em maior taxa de conversão, sem alterar o tempo em que a taxa máxima ocorre; 2) tanto o dispositivo aquecedor quanto os compules atingiram temperaturas inferiores das determinadas pelo fabricante; ao remover o compósito do aquecedor a perda de calor é acentuada ; 3) o grau de conversão não foi afetado por ciclos repetidos e prolongados de pré-aquecimento da resina composta; 4) não houve aumento da temperatura intrapulpar ao serem comparadas as resinas composta à temperatura ambiente e pré-aquecida; 5) a medida da temperatura in vivo revelou que o compósito pré-aquecido a 60 o C fica somente 8 o C acima da temperatura intrabucal; a técnica de pré-aquecimento deve ser usada com cautela. / This work examined multiple aspects of pre-heating dental resin composite prior to light-curing: the monomer conversion and polymerization kinetics as a function of cure temperature, light-exposure duration and depth; the performance of the heating device (maximum temperature, thermal stability of device and temperature change when pre-heating compules); and clinically relevant issues (the effect of repeated and extended pre-heating cycles on conversion; in vitro intrapulpal temperature change and in vivo temperature change when using either room-temperature or pre-heated composite). Monomer conversion and kinetic parameters were determined using FTIR-ATR. Specimens were cured for 5, 10, 20 or 40s between 3 o and 60 o C. Real-time monomer conversion, maximum conversion rate, time into exposure when maximum rate occurred, and conversion at maximum rate were calculated. Data were analyzed using regression analysis, Student's t-tests, and ANOVA with appropriate post-hoc tests (alpha = 0.05). Performance of the heating device was measured by monitoring the real-time temperature change with a K-type thermocouple connected to an analog-to-digital converter. Thermocouples were placed both in the heater and inside composite compules. Data were analyzed using Student t-test (alpha = 0.05). Compules (n=5) were submitted to one of the temperatures cycles: Repeated (from room temperature to 60 o C, 10 times) or Extended pre-heating (24h at 60 o C). Monomer conversion was measured 24h after cycling, with composite at room temperature, following the protocol described above. Data were analyzed using ANOVA and the Tukey-Kramer post-hoc test (alpha = 0.05). Intrapulpal temperature rise was measured by placing a K-type thermocouple in the pulp chamber of a extracted, human premolar, which had a Class V preparation (1mm remaining dentin thickness). The preparation was filled using composite either at room-temperature, or pre-heated while continuously monitoring intrapulpal temperature (n=5). Data were compared using ANOVA and the Tukey-Kramer post-hoc test (α =0.05). For measurement of temperature change in vivo, 2mm deep preparations were made on posterior teeth of a live human subject (n=3). Temperature values were recorded by placing a custom-made probe on the tooth preparation after each restorative procedure and during insertion of resin-composite at room temperature or pre-heated to 60°C. Data were compared using a 2-way ANOVA, and Tukey-Kramer post-hoc test (α =0.05). Results indicated that: 1) pre-warming composite prior to polymerization results in greater conversion, requires shorter exposure duration, and enhances maximal rate of conversion without changing the time into the exposure when the maximum rate occurs; 2) either the heating device or the compules achieved lower temperatures than those stated by the manufacturer; composite temperature loss upon removal from the heater was dramatic; 3) neither repeated nor extended pre-heating of composites significantly affected monomer conversion values; 4) no increase in intrapulpal temperature values was observed when comparing room temperature and pre-heated composite; 5) temperature measurement in vivo revealed that composite pre-heated to 60°C attains only 8 o C above intraoral temperature upon delivery; thus, the composite pre-heating technique should be used with caution.

Made available in DSpace on 2014-08-20T14:30:15Z (GMT). No. of bitstreams: 1 Dissertacao_Fernanda_Barbosa_Leal.pdf: 806160 bytes, checksum: 37717162c453100433c520a8c9d199ef (MD5) Previous issue date: 2012-12-19 / The aim of this study was synthesize, characterize and photopolymerize an alternative monomers for use in dentistry. Three siloxane-oxirane monomers were synthesized and the products conversion was followed by Fourier-transform infrared spectroscopy. The products obtained were characterized by 1H and 13C NMR and evaluated for viscosity and refractive index. The polymerization was evaluated by formulating of two experimental photoinitiation systems wich varied for the presence of 1,2 ethanediol. A ternary system with camphorquinone (CQ), ethyl 4-dimethylaminobenzoate (EDAB) and diphenyliodonium hexafluorphosphate (DPI) was used as control. The degree of conversion was accessed by FTIR and DSC-PCA. The NMR confirmed the synthesis success with 75, 87 and 55% yield for the monomers synthesized. Moreover, the presence of 1,2 ethanediol increase the degree conversion of the siloxane-oxirane monomers. This study showed simple and effective way to synthesize siloxane-oxirane monomers with a high potential for application in dental materials / O objetivo deste estudo foi sintetizar, caracterizar e fotopolimerizar monômeros alternativos para aplicação em Odontologia. Três monômeros siloxano-oxiranos foram sintetizados e a conversão de produtos foi acompanhada por espectroscopia de infravermelho por transformada de Fourier. Os produtos obtidos foram caracterizados por 1H e 13C RMN e avaliados quanto à viscosidade e índice de refração. Para investigar a polimerização, dois sistemas experimentais de fotoiniciação foram formulados, variando quanto à presença de 1,2 etanodiol. Um sistema ternário composto por canforoquinona (CQ), 4-dimetilaminobenzoato (EDAB) e difeniliodonio hexafluorfostato (DPI) foi utilizado como controle. O grau de conversão foi obtido por FTIR e DSC-PCA. As análises de RMN confirmaram a obtenção dos produtos com 75, 87 e 55% de rendimento. Além disso, a presença de 1,2 etanodiol aumentou o grau de conversão dos monômeros siloxano-oxiranos. Este estudo demonstrou um método simples e eficaz para sintetizar monômeros siloxano-oxiranos com grande potencial para aplicação em materiais dentários

La photopolymérisation radicalaire contrôlée (P2RC) est un domaine en plein essor en science des matériaux. En effet, ce procédé permet d’envisager la synthèse de polymères à architecture complexe dans des conditions douces et constitue une approche de choix pour élaborer des couches de polymères microstructurées. Dans ce contexte, l’extension des techniques RAFT, ATRP et NMP à un mode photochimique est principalement étudiée. Au cours de cette thèse, nous nous sommes intéressés en particulier à la technique de NMP2 (Nitroxide Mediated Phototopolymerization). Typiquement nous avons préparé des alcoxyamines photosensibles pour un contrôle de la polymérisation sous irradiation. Une attention spéciale a été portée sur la compréhension du mécanisme régissant le procédé et sur des relations structure/réactivité. De plus les meilleurs candidats ont été testés en NMP2 et plus particulièrement pour la conception de motifs structurés de polymères sur surface. Enfin, de nouvelles approches ont été explorées pour effectuer une NMP2 avec notamment l’ESCP (Enhanced Spin Capturing Polymerization). / Controlled radical photopolymerization represents a rapidly emerging field in material science. This process is characterized by important advantages and provides the possibility to prepare complex polymer architectures in mild conditions such as patterns. In recent years, the development of controlled radical photopolymerizations, such as RAFT, ATRP and NMP, is recognized as particularly interesting and powerful. In this context, we focused our research to the development of the NMP2 polymerization. In line with this research context, the topic of this thesis was to prepare alkoxyamines for a photochemical control. Particular attention has been focused on understanding the mechanism governing the process and structure/reactivity relationships. In addition, the best candidates were tested in NMP2 process and more particularly to the preparation of polymer patterns on surface. Finally, new approaches have been explored to perform NMP2 such as ESCP (Enhanced Spin Capturing Polymerization).

Les matières premières biosourcées s'avèrent être une possibilité de substitution du pétrole de plus en plus prisée dans le domaine des matériaux. De plus, l'utilisation de procédé propre limitant l'impact environnemental du développement de matériau est aujourd'hui incontournable. Dans ce contexte, l'acide aminé L-lysine, un nouveau synthon issu des biotechnologies blanches peu étudié dans le domaine de la chimie des matériaux, a été retenu. Ce synthon sera modifié pour la conception de macromonomères polymérisables sous irradiation UV. En effet, la technique de photopolymérisation est un procédé propre en plein essor, et qui permet le développement de revêtement.La L-lysine étant peu soluble dans les milieux organiques classiques, une étape de transformation est nécessaire pour améliorer sa processabilité. Ainsi, la polycondensation en masse de la L-lysine a conduit à des oligomères de poly-L-lysine de faibles masses molaires. La détermination de la structure obtenue a été réalisée par différentes techniques d'analyses. Ces oligomères sont alors greffés par des fonctions photopolymérisables dans des conditions douces. Le choix s'est porté sur des fonctions accepteur et donneur d'électron. Enfin, l'étude de la photopolymérisation des oligomères de L-lysine greffés accepteurs donneurs a été effectuée par la technique UV aqueuse, une technique innovante et respectueuse de l'environnement, dans différentes conditions pour en optimiser le système. / Biobased raw materials are an interesting and promising option for the substitution of fossil resources in material design. Moreover, using green processes which limit environmental impact of the material conception can't be avoided nowadays. In this context, the L-lysine amino acid, a building block made by white biotechnologies and poorly described in material field has been evaluated. As photopolymerization is a green process in great expansion and allowing coating design, this building block has been modified into a photocurable macromonomer.L-lysine is hardly soluble in usual organic solvents, a transformation step is necessary in order to improve its processability. Thus, L-lysine polycondensation has been tackled and led to oligomers of poly-L-lysine with low molar mass and improved solubility. In addition, the structure determination has been undertaken by different analytic technics. These oligomers can thus be grafted with photocurable functional groups in mild conditions. The chosen photocurable functional groups are donor acceptor of electron. At last, the photopolymerization of L-lysine based oligomers grafted with donor acceptor functional groups has been done by UV waterborne technic which is innovative and environmentally friendly. The photopolymerization has been carried out in different conditions in order to optimize the process.