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Previous issue date: 2016-07-18 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / A s?ntese de pol?meros usando solventes org?nicos e nocivos ao meio ambiente tem sido frequente na comunidade cient?fica. O uso de solventes verdes, como a ?gua, agride menos o meio ambiente. Este estudo proporcionou a s?ntese de dois copol?meros de poli(N-isopropilacrilamida-co-laurato de vinila) com diferentes percentuais molares dos mon?meros na cadeia polim?rica e a avalia??o de suas propriedades. A polimeriza??o foi realizada via radicais livres, substituindo o solvente org?nico, THF, pela ?gua e o iniciador, AIBN, por persulfato de pot?ssio (K2S2O8). Para fins de avalia??o da contribui??o do laurato de vinila nos copol?meros, tamb?m foi sintetizado o homopol?mero de NIPAAm, nas mesmas condi??es reacionais empregadas para os copol?meros. As estruturas qu?micas dos pol?meros obtidos foram investigadas por espectroscopia no infravermelho (IV) e resson?ncia magn?tica nuclear de hidrog?nio (1H RMN) e de carbono (13C RMN). Solu??es aquosas dos pol?meros foram analisadas por reometria, espalhamento de luz est?tico (SLS) e din?mico (DLS). Os resultados obtidos por reometria mostraram que a temperatura cr?tica consoluta inferior (LCST) do poli(N-isopropilacrilamida-co-laurato de vinila) contendo 7 mol% de LV foi de 26 ?C, enquanto a do copol?mero contendo 13 mol% de LV foi de 21 ?C, ou seja, mais baixas que a LCST da PNIPAAm (34 ?C). Esse resultado indica que a presen?a do mon?mero hidrof?bico, LV, contribuiu significativamente para a diminui??o da LCST do pol?mero. A partir do espalhamento de luz est?tico (SLS), calculou-se a massa molar ponderal m?dia aparente ( ?w), o raio de giro (Rg) e o segundo coeficiente virial (A2) dos pol?meros. A ?w e o A2 do poli(N-isopropilacrilamida-co-laurato de vinila) contendo 7 mol% de LV foi de 3,0x106 g/mol e 16,1 mol.L.g-2, respectivamente, enquanto que para o copol?mero contendo 13 mol% de LV, os valores obtidos para ?w e o A2 foram de 2,6x106 g/mol e - 4,27 mol.L.g-2, respectivamente. Para a PNIPAAm, os valores obtidos de ?w e A2 foram 3,2x107 g/mol e 0,69 mol.L.g-2, respectivamente. A diminui??o do valor de ?w dos copol?meros em rela??o ao valor da ?w da PNIPAAm foi atribu?da ? redu??o das intera??es pol?mero-solvente no meio, que foi confirmada pela diminui??o do valor do A2 para os copol?meros. As an?lises de DLS, feitas em concentra??o 1g/L no intervalo de temperatura 15 ?C a 40 ?C, indicaram a presen?a de cadeias isoladas e agregados de diversos tamanhos para os pol?meros em solu??o. / The synthesis of polymers using organic solvents harmful to the environment has been frequent in the scientific community. The use of green solvents, such as water, causes less damage to the environment. This study provided the synthesis of two copolymers of poly (N-isopropylacrylamide-co-vinyl laurate), with different molar percentage of monomers in the polymer chain and the evaluation of their properties. The polymerizations were carried out by free radicals, replacing the organic solvent THF by water, and AIBN initiator by potassium persulfate (K2S2O8). In attempt of evaluating the contribution of vinyl laurate (VL) in copolymers, the NIPAAm homopolymer was also synthesized under the same reaction conditions employed for the copolymers. The chemical structures of the synthesized polymers were determined through infrared (IR) and nuclear magnetic resonance spectroscopy. Aqueous solutions of the polymers were analyzed by rheometry, static light scattering (SLS) and dynamic light scattering (DLS). The results of rheometry showed that lower critical solution temperature (LCST) for poly (N-isopropylacrylamide-co- vinyl laurate) containing 7 mol% of VL was 26 ? C, while the copolymer containing 13 mol% VL was 21 ? C. In other words, lower than the LCST of PNIPAAm (34 ? C). There results indicate that the presence of hydrophobic monomer, VL, contributes significantly in reducing the LCST of the polymer. From the static light scattering (SLS) analysis, it was calculated the weight apparent average molecular weight ( ?w), the radius of gyration (Rg) and the second virial coefficient (A2) of the polymers. The ?w and A2 for poly (N-isopropylacrylamide-co-vinyl laurate) containing 7 mol% of VL were 3.0x106 g/mol and 16.1 mol.L.g-2, respectively, while that for the copolymer containing 13 mol% of VL, the values for ?w and A2 were 2.6x106 g/mol and 4.27 mol.L.g-2, respectively. For PNIPAAm, the values of ?w and A2 were 3.2x107 g/mol and 0.69 mol.L.g-2, respectively. The decrease in the value of ?w of the copolymers relative to the ?w value of PNIPAAm was attributed to the reduction of the polymer-solvent interactions in the medium, which was confirmed by decreasing the value of A2 to the copolymers. Dynamic light scattering (DLS) analysis was performance at polymers concentration of 1g/L in the temperature range 15 ?C to 40 ?C and indicated the presence of isolated chains and aggregates of different sizes for the polymers in solution.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/21972 |
| Date | 18 July 2016 |
| Creators | Dutra, Mariana Alves Leite |
| Contributors | 65946499734, Menezes, Fabricio Gava, 03114939988, Thir?, Rossana Mara da Silva Moreira, 01854587773, Balaban, Rosangela de Carvalho |
| Publisher | PROGRAMA DE P?S-GRADUA??O EM QU?MICA, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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