PHASE-DECOMPOSITION IN BLENDS OF POLYCARBONATE AND ISOTACTIC POLY(METHYL METHACRYLATE)

The dynamics of phase separation and dissolution in a miscible blend of polycarbonate (PC) and isotactic poly(methyl methacrylate) (i-PMMA) has been investigated by means of time-resolved light scattering. The PC/i-PMMA system reveals a reversible lower critical solution temperature (LCST). Several temperature jumps were undertaken from a single phase into an immiscible two-phase region. The time evolution of scattering curves shows no movement of the peak for a considerable period as predicted by the linearized Cahn-Hilliard theory developed for spinodal decomposition. The late stage of phase decomposition follows a power law with an exponent of 1/3 in the growth of fluctuations versus time plots. The kinetic study was extended to the phase dissolution process by conducting temperature quench experiments. The results were analyzed in terms of a simple Fickian diffusion. Finally, the universal scaled curves were compared at the critical compositions of PC/i-PMMA and PC/h-PMMA (heterotactic poly(methyl methacrylate)) to elucidate the influence of tacticity.