Kinetics of phase separation of poly(styrene-co-methy methacrylate) and poly(styrene-co-acrylonitrile) blends

The phase behavior and kinetics of phase separation for blends of the random copolymer poly(styrene-co-methyl methacrylate) (SMMA) and poly(styrene-co-acrylonitrile) (SAN) were studied by using small-angle laser fight scattering. The partially miscible SMMA/SAN blends undergo spinodal decomposition (SD) and subsequent domain coarsening when quenched inside the unstable region. For blends of SMMA and SAN, the early stages of the phase separation process could be observed, unlike a number of other blends where the earliest stages are not visible by light scattering. The process was described in terms of the Cahn-Hilliard linear theory. Subsequently, a coarsening process was detected and the time evolution of q(m) at the beginning of the late stages of phase separation followed the relationship q(m) proportional to t(-1/3), corresponding to an evaporation-condensation mechanism. Self-similar growth of the phase-separated structures at different timescales was observed for the late stage. (C) 2004 Society of Chemical Industry.