Uma nova rota de obtenção de poli(n-isopropilacrilamida-co-laurato de vinila) e sua caracterização físico-química em meio aquoso

• Ano de defesa: 2016
• Autor(a) principal: Dutra, Mariana Alves Leite
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Brasil; UFRN; PROGRAMA DE PÓS-GRADUAÇÃO EM QUÍMICA
• Palavras-chave em Português: poli(N-isopropilacrilamida); poli(N-isopropilacrilamida-co-laurato de vinila); FTIR; RMN; Reometria; SLS; DLS; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA
• Link de acesso: https://repositorio.ufrn.br/jspui/handle/123456789/21972

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.