SPINODAL DECOMPOSITION INDUCED BY COPOLYMERIZATION IN THE MIXTURE OF METHYL-METHACRYLATE VINYL-ACETATE POLY[ETHYLENE-CO-(VINYL ACETATE)]

Phase separation during copolymerization of a mixture of methyl methac rylate/vinyl acetate/poly[ethylene-co-(vinyl acetate)] (MMA/VAc/EVA) i s investigated by time-resolved light scattering (TRLS) and scanning e lectron microscopy (SEM). TRLS investigation shows that a phase separa tion takes place via spinodal decomposition (SD) when polymerization i n a mixture of MMA/VAc/EVA as well as of MMA/EVA proceeds. Scattering profiles with double-peak feature develop in the case of SD induced by copolymerization in MMA/VAc/EVA mixtures, whereas only a single peak occurs in the MMA/EVA copolymerization. Moreover, it is shown that the process of SD during polymerization is different from that in ordinar y thermally-induced SD, i.e. q(m), the wavenumber q at the peak positi on of the scattering profile, remains virtually invariant with time. S EM observation show that the unique morphologies are obtained ultimate ly during SD induced by polymerization in MMA/EVA and MMA/VAc/EVA mixt ures. For the polymerized MMA/EVA mixture, PMMA-rich particles with a uniform size and distribution are dispersed in the matrix of an EVA-ri ch phase, whereas for polymerized MMA/VAc/EVA mixtures, MMA-VAc copoly mer rich particles are finely dispersed in an EVA-rich phase as matrix with bimodal distribution of sizes, i.e. uniform small domains and la rger domains are obtained simultaneously, which is consistent with the results of the double peak observed in light scattering profiles.