Estudo da formação de micelas reversas em sistemas de tensoativos não iônicos/solventes orgânicos

Abstract

Unlike studies about the formation of direct micelles, which can be evaluated with simple techniques such as conductivity and surface tension, it is difficult to obtain good and reproducible data when it comes to the formation of reverse micelles. In recent decades, reverse micelles have been systematically used as templates for the synthesis of nanomaterials, due to their ability to self-aggregate in diverse structures, passing these characteristics to the desired material. Therefore, the present work had the objective of studying the effect of carbon chain length variation of the solvent, the degree of ethoxylation of the surfactants and the temperature in the formation of reverse micelles, with respect to the structural characteristics and micelar concentration critical (c.m.c.). Small angle X-ray scattering was used to evaluate the micellar systems and nonylphenol ethoxylate surfactant was chosen as solute, being used solvents of different carbon chain length. A wide range of solvent-surfactant combinations were analyzed, the main results show that increasing the ethoxylation degree of the surfactant causes a decrease in c.m.c.. The maximum dimensions of the micellar aggregates followed an increase both with the positive variation of the degree of surfactant ethoxylation with: the increase of the carbon chain of the solvents, and the carbon chain length of the surfactant and the temperature. As regards the formats acquired by the aggregates, there was a predominance of flat structure variation, passing through a solid spherical and hollow spherical structure when concentration surfactant was reduced in the system.