Estudo de parâmetros de síntese do gel termossensível Poli(N-isopropilacrilamida).

Abstract

In this work, the main parameters involved in the Poly (N-isopropylacrylamide) temperature-sensitive gel synthesis were studied, in order to evaluate their influence in the characteristics of the obtained gel. This study contributed to elucidate an importantaspect relative to this gel synthesis, considering that, differently from previous works around the same theme, a simultaneous variation of the synthesis parameters was done and the results were statisticaly analysed and physically discussed. The studied parameters were the concentration of the main monomer, the concentration of the crosslinking agent, the concentration of initiators and the synthesis temperature.The results were analyzed by using a kinetic variable, the gelation time, and two thermodynamic variables, the volumetric degree of swelling and the phase transition temperature. An experimental statistical planning was done, by using a 24 factorial planning, involving the four parameters studied and two levels for each one. It resulted on an experimental matrix with sixteen systems, corresponding to the sixteen synthesized gels.The obtained results allowed an analysis according to three lines: an statistical analysis, a qualitative analysis of the effects considering the theory of polymerization and a qualitative analysis according to the theoretical kinetic model for copolymerization via free radicals.The main variable analyzed was the gelation time. A strong effect of the crosslinking agent concentration and of the synthesis temperature was observed. The higher the value of each of these parameters, the lower the gelation time. It was also observed a strong conjugated influence of these parameters.