A depolarized light scattering study of the phase separation process in an epoxy-elastomer blend

Abstract : Phase separation between two or more isotropic polymers is usually studied by unpolarized or polarized light scattering (SALS). Depolarized SALS has never been used, but it is also able to bring useful information about the kinetics and mechanisms of the phase separation. Such a new technique is tested here by studying the evolution of a phase separation in a pseudo-binary mixture of bis-phenol A diglycidylether (epoxy monomer), a cycloaliphatic diamine (comonomer or cross-linking agent) and an epoxy terminated butadiene-acrylonitrile random copolymer (additive). The depolarized light scattering patterns during the phase separation have four lobes positioned at 45 ° of the position of the polarizers. The position of the lobes does not vary with time, suggesting that the mechanism of spinodal decomposition is responsible for the phase separation. The resulting periodic distance between composition fluctuations is calculated from the position of the lobes using two methods. It was found in agreement with the distance deduced from the position of the scattering ring observed in unpolarized light scattering.