Made available in DSpace on 2014-06-11T19:28:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-10-03Bitstream added on 2014-06-13T20:37:56Z : No. of bitstreams: 1 mancuso_dn_me_araca.pdf: 2113835 bytes, checksum: 27a105a29a2894608038cc448f18dd65 (MD5) / Universidade Estadual Paulista (UNESP) / O objetivo desta pesquisa foi o de avaliar a estabilidade de cor dos silicones faciais pigmentados e não pigmentados após o envelhecimento acelerado. Foram utilizados dois silicones, sendo um de fabricação estrangeira, próprio para próteses faciais, e um silicone acético de fabricação nacional, de uso industrial. Foram confeccionados 24 corpos-de-prova para cada silicone, divididos em grupos incolor e pigmentados intrinsecamente com: cerâmica; maquiagem; óxido de ferro. Os grupos foram submetidos ao sistema acelerado de envelhecimento para não-metálicos - ultravioleta B / condensação (Comexim, Brasil). Foi feita leitura inicial e após períodos correspondentes a 163, 351, 692 e 1000 horas de envelhecimento, através do método visual de comparação e da análise por espectrofotômetro de reflexão Color-Eye (MacBeth, USA), utilizando o Sistema CIE L*a*b*. Os valores foram submetidos à análise de variância e teste de Tukey em nível de 5% de probabilidade. Todos os grupos apresentaram estabilidade de cor no método visual de comparação. Mas, com relação à espectrofotometria de reflexão, após as 1000 horas de envelhecimento acelerado, tanto o 732 RTV, quanto o MDX, pigmentados com maquiagem, apresentaram alteração de cor. Para o grupo incolor, em 351 horas de envelhecimento, tanto o 732 RTV, quanto o MDX, apresentaram alteração. Conclui-se então que os dois silicones possuem boa estabilidade de cor em todos os grupos estudados, com exceção da maquiagem que foi considerada a mais instável dentre os pigmentos para os dois silicones. / The objective of this research was evaluating the color stability of the facial silicones pigmented and without pigmentation after the accelerated aging. A foreign silicone created specifically for facial prostheses and a national acetic silicon for industrial use were used in research. 20 bodies-of-proof were made for each silicone, divided in colorless and intrinsically pigmented groups with: ceramic; make-up; oxide of iron. The groups were submitted to the accelerated System of aging for no-metallic - Ultraviolet B / condensation (Comexim, Brazil). An initial evaluation and evaluations after 163, 351, 692 and 1000 hours of aging were made. The visual method of comparison and the analysis for reflection spectrophotometer Color-Eye (MacBeth, USES) were used with the CIE L*a*b * System. The values were submitted to the variance analysis and Tukeyþs test in level of 5% of probability. All groups presented color stability in visual method. After 1000 hours of accelerated aging, Silastic 732 RTV and MDX, both pigmented with make-up presented color change in spectrophotometer analysis. The Silastic 732 RTV and MDX colorless groups presented color change in 351 hours of aging. It was concluded that all groups of both silicones had good color stability, except make-up group that was considered the most unstable pigment for both silicones.

Made available in DSpace on 2014-06-11T19:35:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-12-20Bitstream added on 2014-06-13T19:05:10Z : No. of bitstreams: 1 guiotti_am_dr_araca.pdf: 4282150 bytes, checksum: e2af8fc731eff076677463685ecc36bc (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O insucesso das próteses faciais é causado pelas limitações das propriedades dos materiais existentes, sendo as mais críticas a flexibilidade e a durabilidade. Uma prótese facial deve ser resistente e ter longa duração, mas se manter suave e flexível para acompanhar os movimentos faciais do paciente. Diante destas considerações, o objetivo desta pesquisa foi o de avaliar a deterioração marginal e a dureza SHORE A de dois silicones para uso em prótese facial - o Silastic 732 R.T.V. e o Silastic MDX4-4210, sob a influência do tempo de armazenagem, da desinfecção diária com clorexidina a 2% e de dois tipos de pigmentação, considerando que sempre houve a necessidade de um material que combinasse a flexibilidade natural da pele humana com durabilidade no seu uso. Foram confeccionados 30 corpos-de-prova para cada material, divididos em 3 grupos: controle (incolor), pigmentados com maquiagem e com óxido de ferro. A análise da deterioração marginal foi realizada em microscópio eletrônico de varredura e o teste de dureza dos materiais foi realizado em durômetro SHORE A, imediatamente, 6 meses e um ano após a confecção dos corpos-de-prova, seguindo as especificações da ASTM. Os dados da dureza foram submetidos à análise estatística, utilizando-se do teste de Tukey com nível de 99% de confiabilidade. Os dois silicones para uso facial apresentaram um aumento da sua dureza SHORE A com o passar do tempo. Entretanto, a dureza SHORE A manteve-se estável no período de 6 meses a 1 ano. Quando os silicones foram comparados entre si, o Silastic 732 R.T.V. mostrou-se estatisticamente mais flexível que o MDX4-4210. Após a análise visual das fotomicroscopias (aumento de 1000x) foi possível perceber que todos os grupos sofreram deterioração marginal e alteração de sua textura superficial com o passar do tempo... / Prosthetic failure can be attributed to the inherent problems of the properties of materials, such as flexibility and durability. The maxillofacial prosthesis must be strong and have durability, but must be soft and flexible enough to respond to the facial motions of the patient. The purpose of this study was to analyse the influence of time s storage, chemical disinfection with 2% chlorhexidine-based solution and two distincts pigments about marginal deterioration and SHORE A hardness of two silicones for use in maxillofacial prosthesis - the Silastic 732 R.T.V. and the Silastic MDX4-4210. Thirty specimens were fabricated for each silicone using a matrix. Specimens were separated in three groups: control (colourless), pigmented with commercial cosmetic (makeup powders) and pigmented with iron oxid. The marginal deterioration analysis was realized in scanning electron microscope (SEM) and the hardness test was realized in a SHORE A durometer, according to ASTM, designation D 2240. The readings were realized after polymerization of the specimens (initial period), after 6 months and 1 year, with and without disinfection. The data of SHORE A hardness were submited to the statistic analysis, by the Tukey s Test. Both silicones presented an increase of hardness over time. However, the hardness maintained stable at 6 months and 1 year periods. When both silicones were compared, the Silastic 732 R.T.V. showed statistically softer than MDX4-4210. After visual analysis of photomicrocopies (1000x), was possible note that all groups suffered marginal deterioration over time. The chemical disinfection also contributed to marginal deterioration of silicones, independent of time and pigmentation. Subject to the design, materials and methods used in this research, the following conclusions can be drawn:...(Complete abstract, click electronic address below)

O objetivo do presente estudo foi identificar, clinicamente, os micro-organismos presentes em próteses e tecidos adjacentes, avaliar laboratorialmente a ação antimicrobiana de diferentes protocolos de higiene sobre os principais micro-organismos identificados e, ainda, avaliar a influência dos protocolos de higiene na alteração de cor, dureza Shore A, rugosidade superficial e absorção de líquidos, de um novo silicone (Bio-Skin), em comparação ao MDX 4-4210. Para identificação dos micro-organismos, 43 indivíduos portadores de próteses maxilofaciais foram submetidos à colheita do biofilme na região da prótese e tecidos adjacentes e 38 espécies alvos de micro-organismos foram pesquisadas por meio do método de hibridação de DNA Checkerboard. A análise da ação antimicrobiana foi conduzida por meio da formação de biofilmes específicos de 6 espécies selecionadas. 288 espécimes pigmentados com pó de maquiagem foram confeccionados com cada material, e distribuídos em grupos para imersão em gluconato de clorexidina a 0,12%, Ricinus communis a 10%, e escovação com sabão neutro. Como controle, um grupo foi imerso em água. Para análise da influência dos protocolos de higienização nas propriedades dos silicones, 120 corpos de prova circulares de cada material foram confeccionados (n=10): sem pigmentação (GC: controle), com pó de maquiagem (GP), opacificador (GO) ou opacificador + pó de maquiagem (GPO), para então serem submetidos à higienização: EA (imersão em água destilada + escovação com sabão neutro controle), ERc10% (imersão em solução de Ricinus communis 10% + escovação com sabão neutro) e ECl0,12% (imersão em gluconato de clorexidina 0,12% + escovação com sabão neutro). O período de higienização simulou um ano de uso clínico. As variáveis de resposta quantitativas foram mensuradas imediatamente após a obtenção dos espécimes e após a aplicação dos protocolos de higiene e a variação obtida foi utilizada na análise estatística. Para análise da ação antimicrobiana dos protocolos de higiene e para alteração de cor, dureza Shore A e rugosidade superficial, realizou-se Análise de variância e Teste Complementar de Tukey para comparação das médias. Para a absorção de líquidos, aplicou-se o Teste de Kruskal-Wallis. Para comparação da contagem de micro-organismos presentes nas próteses e tecidos adjacentes empregou-se o Teste de Wilcoxon (Signed-rank Test). Para análise dos dados obtidos pela contagem de UFC, para análise da ação antimicrobiana dos protocolos de higiene, empregou-se Two-way ANOVA e Teste Complementar de Tukey. Todas as análises foram conduzidas com nível de significância 5%. O método de hibridação de DNA Checkerboard indicou a presença das 38 espécies nas próteses e tecidos adjacentes e foram selecionados os seguintes micro-organismos: C. glabrata, S. aureus, S. mutans, E. coli, E. faecalis e P. aeruginosa. Para a análise antimicrobiana, o gluconato de clorexidina a 0,12% foi o mais eficaz, seguido pela escovação mecânica, contra as 6 espécies. A alteração de cor não foi influenciada pelos protocolos de higiene e a menor alteração foi encontrada com o silicone Bio-Skin dos grupos GP e GPO. O silicone MDX apresentou menor variação de dureza Shore A em função do protocolo de higiene ECl0,12%, enquanto a dureza do Bio-Skin não foi influenciada pelos protocolos de higiene. A variação da dureza entre os dois silicones foi diferente somente quando submetidos ao protocolo ERc10%. Para a rugosidade superficial, o silicone MDX apresentou a menor variação de rugosidade. A porcentagem de absorção de líquidos do silicone MDX 4-4210 não foi influenciada pela pigmentação ou protocolos de higienização. Para o Bio-Skin, a porcentagem de absorção foi maior nos grupos GC e GO quando submetidos ao protocolo EA. Nota-se que houve uma interação entre pigmento e protocolo de higiene, onde para o silicone MDX, a absorção foi maior quando submetidos ao protocolo ECl0,12% e para o Bio-Skin, houve uma maior porcentagem de absorção nos grupo GC e GO associados à escovação e imersão em água e nos grupos GP e GPO associado ao protocolo ECl0,12%. Conclui-se que tanto as próteses quanto os tecidos adjacentes apresentam grande quantidade de micro-organismos colonizadores e que cuidados diários de higiene são essenciais. Os protocolos de imersão em gluconato de clorexidina a 0,12% e de escovação mecânica com sabão neutro possuem efetividade antimicrobiana sobre os principais micro-organismos comumente presentes em próteses e tecidos e o silicone MDX 4-4210 apresentou menor contagem de UFC quando comparado ao Bio-Skin. Ambos os materiais apresentaram variações em função das diferentes pigmentações e protocolos de higiene, entretanto, as mesmas foram discretas e dentro de padrões clínicos aceitáveis. As menores alterações foram observadas quando os materiais foram expostos aos protocolos de imersão em gluconato de clorexidina a 0,12% e escovação com sabão neutro. / The aim of this study was to identify clinically the microorganisms present in prostheses and adjacent tissues, evaluated laboratory antimicrobial action of different hygiene protocols on the main identified microorganisms and also evaluate the influence of hygiene protocols in color change, Shore A hardness, surface roughness and absorption of liquids, a new silicon (Bio-Skin) compared to the MDX 4-4210. For identification of microorganisms, 43 individuals with maxillofacial prostheses were submitted to harvesting the biofilm on the prosthesis and adjacent tissues and 38 targets species were surveyed through the Checkerboard DNA-DNA Hybridization method. The analysis of antimicrobial activity was conducted by formation of specific biofilm in six selected species. 288 specimens with pigmented makeup powder were fabricated with each material, and divided into groups for immersion in 0.12% chlorhexidine gluconate, Ricinus communis 10%, and brushing with neutral soap. As a control, one group was immersed in water. To analyze the influence of hygiene protocols on the properties of silicones, 120 circular specimens of each material were prepared (n = 10): no pigmentation (CG: control), with makeup powder (GP), opacifier (GO) or opacifier + makeup powder (GPO), and then be submitted to cleaning: EA (immersion in distilled + brushing water with mild soap - control), ERc10% (immersion in Ricinus solution communis 10% + brushing with mild soap) and ECl0 12% (immersion in chlorhexidine gluconate 0.12% + brushing with neutral soap). The hygiene period simulated one year of clinical use. The quantitative response variables were measured immediately after obtaining the specimens and after the application of hygiene protocols and the variation obtained was used in the statistical analysis. For analysis of antimicrobial hygiene protocols and color change, Shore A hardness and surface roughness, there was analysis of variance and Tukey Supplementary test for comparison of averages. For the absorbing liquid, we applied the Kruskal-Wallis test. For comparing the count microorganisms present in prostheses and adjacents tissues we used the Wilcoxon test (Signed-rank Test). To analyze the data obtained by CFU counts for analysis of antimicrobial hygiene protocols, we used two-way ANOVA and Tukey Complementary Test. All analyzes were conducted with significance level of 5%. The method of Checkerboard DNA-DNA Hybridization indicated the presence of 38 species in the prosthesis and adjacent tissue and the following microorganisms were selected: C. glabrata, S. aureus, S. mutans, E. coli, E. faecalis and P. aeruginosa. For antimicrobial analysis, 0.12% chlorhexidine gluconate was the most effective, followed by mechanical brushing, against six species. The color change was not influenced by hygiene protocols and the slightest change was found with the Bio-Skin silicone GP and GPO groups. Silicone MDX showed less variation in Shore A hardness according to the maintenance protocol ECl0,12%, while the hardness of Bio-Skin was not influenced by hygiene protocols. The variation in hardness between the two silicones were different only when subjected to ERc10% protocol. To the surface roughness, the MDX silicone showed the smallest variation of roughness. The percentage of absorption for the MDX 4-4210 silicone was not influenced by the pigment and sanitization protocols. For the Bio-Skin, the percentage of absorption was higher in GC and GO groups when subjected to EA protocol. Note that there was an interaction between pigment and maintenance protocol, where for silicone MDX, absorption was greater when subjected to ECl0,12% protocol and Bio-Skin, there was a greater percentage absorption in the GC group and GO associated with brushing and immersion in water and GP groups and GPO associated with ECl0,12% protocol. It was concluded that both prosthesis as adjacent tissues exhibit great amount of microoorganisms colonizing and that daily hygiene are essential. The immersion in chlorhexidine gluconate 0.12% and mechanical brushing protocols with neutral soap have antimicrobial activity on the main microorganisms commonly present in prosthetics and tissue and silicone MDX 4-4210 had lower CFU counts compared to Bio Skin. Both materials showed variations due to different pigmentations and hygiene protocols, however, they were discreet and within acceptable clinical standards. Minor changes were observed when the materials were exposed to immersion protocols chlorhexidine gluconate 0.12% and brushing with neutral soap.

Orientador: Leila Peres / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-14T23:42:14Z (GMT). No. of bitstreams: 1 Ribeiro_SimoneRodrigues_M.pdf: 4316157 bytes, checksum: d8b454c7552b53ef41d86b66929ff0b3 (MD5) Previous issue date: 2009 / Resumo: Compósitos poliméricos são materiais que têm atraído cada vez maior atenção dos cientistas, assim como da indústria. "Release liners" são materiais com propriedade antiaderente utilizados para proteger a(s) face(s) adesiva(s) de uma fita adesiva, substrato e rótulos adesivos, sendo compostos basicamente de papéis revestidos de uma camada de silicone, que os tornam não-biodegradáveis, resultando em materiais pós-uso de longa vida. Em 2007 o mercado total mundial de "release liners" atingiu 30 bilhões de metros quadrados, sendo a sua disposição primariamente em aterros sanitários. O presente trabalho tem como proposta o desenvolvimento de uma alternativa de reuso deste material, através da sua utilização em um compósito baseado em "release liner" triturado incorporado a uma matriz polimérica de PVC. Seu desempenho foi comparado com o de um compósito formado por papel sem silicone e PVC. As propriedades desses materiais foram avaliadas por meio de ensaios mecânicos de resistência à tração (tensão e alongamento na ruptura) e resistência à abrasão. A morfologia do compósito foi investigada por meio de microscopia ótica e microscopia eletrônica varredura (MEV) de forma a entender melhor a correlação entre estrutura e propriedades. Ensaios de análise térmica (TGA) como também testes de resistência à chama e de absorção de umidade foram realizados com a intenção de observar a influência da presença de "release liners" na matriz polimérica. Os resultados de análise térmica mostraram um aumento de resistência térmica dos compósitos com "release liner" em relação à matriz polimérica de PVC. Embora a resistência mecânica dos compósitos tenha se mostrado inferior à matriz de PVC, devido à deficiência de compatibilidade, houve melhores resultados de resistência à abrasão do compósito quando comparado com o PVC, o que indica uma possível aplicação em revestimentos e a viabilidade da reciclagem do "release liner" sem prévia separação em silicone e fibras de celulose. / Abstract: Polymeric composites were given a huge attention from scientists as well as from the industry. "Release liners" are materials with anti-adherent properties used to protect the adhesive faces of adhesives tapes, adhesive subtract or adhesives labels, basically composed by papers coated with a silicone layer, which makes them non-biodegradable resulting in a long life after their use. In 2007 the total worldwide release liner market was around 30 billion sqm. Their mainly disposal is primary into land fills. The present work aims at the development of an alternative to reutilization this material, thought its utilization in a composite based on grinded liner incorporated in PVC polymeric matrix. The performance was compared to a PVC composite made by paper without silicone and PVC. The properties of these materials were analyzed through mechanical analysis of traction resistance (strain and elongation on rupture), and abrasive resistance. The composite morphology was investigated with the use of optical microscopy and scanning electronic microscopy (SEM) in order to better understand the correlation between structure and properties. Thermo gravimetric analyses (TGA) tests were also performed with the objective to assess the influence of the presence of "release liners" in PVC polymeric matrix. Additionally, flame resistant tests and moisture absorption tests were conducted in order to observe the influence of presence of release liners in polymeric matrix. TGA results have shown a thermal resistance increase of composites content release liners when compared to composites with PVC polymeric matrix. Although the composites mechanical resistance has shown inferior results, when compared to PVC matrix, due to compatibility deficiency, there was higher abrasion resistance composites compared to PVC, which indicates a possible application in covering the viability to recycle "release liners" without previous splitting between silicone and cellulose fibers. / Mestrado / Ciencia e Tecnologia de Materiais / Mestre em Engenharia Química

L'hydrosilylation des alcènes est une méthode cruciale de formation de liaisons carbone-silicium. Elle est utilisée industriellement pour la production de fluides silicones fonctionnels et d'élastomères silicones. Les procédés actuels d'hydrosilylation des alcènes utilisent des complexes de platine comme catalyseurs. Bien que ces complexes soient extrêmement efficients, ils ne sont d'habitude pas récupérés en fin de réaction, ce qui rend leur utilisation coûteuse et peu durable, étant donnée la rareté du platine. Dans ce projet, nous avons synthétisé et testé plusieurs types de nanoparticules métalliques comme catalyseurs pour l'hydrosilylation des alcènes, dans un effort vers des catalyseurs durables. D'abord, nous avons synthétisé des nanoparticules de platine de 2 nm de diamètre et les avons comparées avec le complexe de Karstedt, le catalyseur de référence en hydrosilylation des alcènes. Nous avons montré que les nanoparticules de platine étaient aussi efficientes que le complexe de Karstedt dans des conditions proches des conditions industrielles, malgré leur dispersion métallique plus faible. Ces observations ont réactivé le débat sur la nature réellement homogène ou colloïdale du complexe de Karstedt pendant la catalyse. Ensuite, un catalyseur hétérogène à base de platine, résistant à la lixiviation, a été développé, basé sur l'encapsulation de nanoparticules de platine dans la matrice d'une silice mésostructurée, la SBA-15. Enfin, d'autres catalyseurs alternatifs ont été développés, basés sur d'autres métaux / Alkene hydrosilylation is a crucial method of forming carbon-silicon bonds. It is used industrially for the production of functional silicone fluids and silicone elastomers. The current industrial alkene hydrosilylation processes use platinum complexes as catalysts. Although these complexes are extremely efficient, they are usually not recovered at the end of the synthesis, making their use expensive and unsustainable, given the scarcity of platinum. In this work, we have synthesized and evaluated several kinds of metal nanoparticles as catalysts for alkene hydrosilylation, in a quest towards sustainable catalyts. First, we have synthesized platinum nanoparticles of 2 nm diameter and compared them with Karstedt's complex, the benchmark catatalyst in alkene hydrosilylation. It was shown that platinum nanoparticles were as efficient as Karstedt's complex in industrially relevant hydrosilylation conditions, despite their lower metal dispersion. These findings reactivated the debate on whether's Karstedt's complex was truly homogeneous or colloidal during catalysis. Then, a leaching-resistant heterogeneous platinum catalyst was developed, based on the embedding of platinum nanoparticles in the matrix of a mesostructured silica, SBA-15. Finally, other alternative catalytic systems were developed, based on other metals

<p>Silicones are a class of polymeric materials broadly used in numerous commercial applications, primarily due to the significant advantages they poses over their carbon-based analogues. The technology utilized to synthesize them is rather mature, and most ‘new’ synthetic strategies involve only incremental changes to the existing norm. The high level of structural control that has become the hallmark of organic synthesis and increasingly of polymer chemistry is essentially absent from silicone chemistry. The origin of this deficiency is the susceptibility of silicone polymers to redistribution (metathesis/rearrangement) under acidic and basic conditions, which will destroy any existing controlled architectures. The Piers-Rubinsztajn reaction, catalyzed by tris(pentafluorophenyl)borane (B(C₆F₅)₃), involves the direct coupling between an alkoxysilane and hydrosilane forming a new siloxane linkage, (R₃Si-OMe + H- SiR’₃ → R₃Si-O-SiR’₃ + Me-H). The reaction avoids any unwanted acidic/basic reaction conditions and has been shown previously to provide an efficient route to precise, well-defined silicones.</p> <p>Herein, the functional tolerance of the Piers-Rubinsztajn reaction is reported. It has been shown that in the presence of Lewis basic functional groups (such as – OH, -NH₂, -SH) unwanted side reactions result. However in the presence of haloalkanes and alkenes the reaction is fully tolerant, leading to the synthesis of over twenty new, well-defined functional silicones.</p> <p>The ability to utilize prepared functional silicones in common organic transformations is also reported. It has been shown that prepared halocarbon- modified silicones can readily be converted to their subsequent azido derivatives and tethered to alkyne-modified poly(oxyethyene) (PEG or PEO) of a variety of molecular weights. This led to the synthesis of over fifteen new, well-defined silicone surfactants. Structure activity relationships have also been reported for the synthesized surfactants, showing that subtle manipulations to the silicone hydrophobe can substantially alter the properties the surfactants possess. The use of thiol-ene click chemistry which involves the reaction between prepared well-defined alkene containing silicones and thiol modified poly(oxyethylene) of varying molecular weights is also reported, providing another route to well- defined silicone based surfactants.</p> <p>The use of the Piers-Rubinsztajn reaction in the synthesis of larger, well-defined silicone based macrostructures is also reported. It has been shown that through alternation between the Piers-Rubinsztajn reaction and platinum catalyzed hydrosilylation, well defined silicone dendrimers can be obtained with relative ease through a combination of both divergent and convergent growth methods.</p> <p>Finally, a new method for the preparation of both silicone elastomers and silicone foams is reported. Through use of the Piers-Rubinsztajn reaction, elastomers can be readily obtained. A detailed analysis of the many factors that may alter the overall properties of the elastomers produced including solvent volume, crosslinker concentration and type and the molecular weight of the starting hydride terminated polydimethylsiloxane (H-PDMS-H) is discussed.</p> <p>Taking advantage of the volatile hydrocarbon byproducts of the Piers-Rubinsztajn reaction, silicone foams can also be prepared using this method. A study analogous to that carried out on the silicone elastomers is also reported, showing that through subtle manipulations to the silicone foam formulations, significant changes to the materials properties can be obtained.</p> / Doctor of Science (PhD)

Silicones elastomers are widely used all over the world due to their unusual properties when compared to their carbon-based counterparts. Synthetic methods for their synthesis are still quite limited and the traditional silicone products are not able to completely meet the requirement for modern materials. Silicone elastomers with customized structures and with higher levels of sustainability will be the research focus for the development of next generation materials. The element sulfur and its functional groups are growing players in modern polymer and materials science, since sulfur reactions are exceptionally versatile. The incorporation of sulfur reactions into the design and preparation of silicone materials can lead to silicones with unique properties for various research interests. Initial exploration was focused on the creation of general and simple methods for 3D printing silicone elastomers using thiol-ene chemistry. However, silicone inks suitable for 3D printing are still quite limited. Photo-initiated thiol-ene chemistry was proposed to design a rapid cure silicone ink for extrusion 3D printing. Unlike other radical reactions, the relatively oxygen insensitive thiol-ene was able to provide the necessary rapid reaction rate and build up the necessary viscosity for practical printing in less than 2 seconds in the presence of air. Various customized silicone structures with different moduli were obtained with a relative fast printing speed. The use of thiol oxidation reactions in the synthesis of silicone elastomers is also demonstrated in this thesis. Reductive cleavage of the resulting disulfide bridge was successfully performed with the presence of hydrosilane and B(C6F5)3 catalyst. Herein, a synthetic method to reversible silicone elastomers based on the disulfide linkage is described. This method could be extended to cleave the disulfide and polysulfide linkage in used automotive rubber materials. Various kinds of sulfur-cured rubbers were successfully devulcanized to polymeric oil. This simple and efficient method could potentially offer a solution for the huge amount of tire waste produced every year. Finally, a new method for preparing thermoplastic silicone elastomers with ionic linkages is reported. A novel dicarboxylic acid-modified silicone was synthesized though thiol-Michael additions. The resulting ionic crosslinked networks were built though the neutralization between carboxylic and amino silicone. Thermoplastic silicone elastomers with unique viscoelastic behavior can be obtained. In summary, the thesis demonstrates that sulfur chemistry is an exceptional synthetic tool for the silicone chemist. / Thesis / Doctor of Philosophy (PhD)

Foram preparadas redes poliméricas com propriedades elastoméricas de poli(dimetilsiloxano) (PDMS) funcionalizadas com os grupos tiol ou sulfônico. Os materiais preparados foram caracterizados por Espectroscopia na região do Infravermelho (IV), Análise Termogravimétrica (TG), Calorimetria Diferencial de Varredura (DSC), Difração de Raios X (DRX) e Ressonância Magnética Nuclear de 13C e 29Si (RMN). Os resultados destas análises sugerem que os materiais foram funcionalizados com os grupos citados e que são constituídas de segmentos lineares de PDMS reticulados por nós silsesquioxanos que contém silícios do tipo T3 e/ou T2. As redes poliméricas se apresentam no estado amorfo e com alta estabilidade térmica em atmosfera inerte. A potencialidade dos materiais como adsorventes de íons metálicos de soluções etanólicas foram avaliadas obtendo-se isotermas de adsorção para o íon Cd2+. O material com o grupo ácido sulfônico apresentou maior eficiência em reter este metal quando comparado com os materiais contendo o grupo tiol. A quantidade total de cádmio adsorvido foi de 0,89 mmol g-1 e 0,33 mmol g-1, respectivamente. Pelo estudo da linearização dos dados das isotermas, o modelo que melhor representa a interação adsorvente-adsorvato para os materiais preparados é o descrito por Langmuir. / Poly (dimethylsiloxane) (PDMS) networks functionalized with thiol or sulfonic groups have been prepared. The materials were characterized by Infrared Spectroscopy (IR), Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), X-Ray Diffraction (XRD) and 13C / 29Si Nuclear Magnetic Resonance (NMR). The results suggest that the materials were functionalized with above cited groups and the networks are constituted of linear segments of PDMS crosslinked by nodes of silsesquioxanes which contains T3 and/or T2 silicon types. The polymeric networks are in an amorphous state and with high thermal stability, when in an inert atmosphere. The potential of the materials to act as adsorbents for metal ions from ethanol solutions were studied by obtaining adsorption isotherms for Cd2+ ion. The material functionalized with the sulfonic group was the most efficient when compared to the thiol group. The total amount of cadmium adsorbed was 0.89 mmol g-1 and 0.33 mmol g-1, respectively. Evaluation of the linearized isotherms data shows that the model which better represents the interaction between the adsorbate-adsorbent for the prepared materials is the described by Langmuir. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES

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Thesis (M.Sc. (Environmental Science and Management)--North-West University, Potchefstroom Campus, 2008