DYNAMIC ASPECTS OF PHASE-DECOMPOSITION IN REACTIVE BLENDS OF POLYCARBONATE AND SYNDIOTACTIC POLYMETHYL METHACRYLATE

Dynamics of phase separation in bisphenol-h polycarbonate (PC)/syndiot actic polymethyl methacrylate (sPMMA) blends has been investigated by means of time-resolved light scattering. Solvent-cast films of the PC/ sPMMA blends were transparent, suggestive of miscible character. Sever al temperature jumps were carried out at a 50/50 PC/sPMMA composition from a homogeneous state (room temperature) into a two-phase regime. T he process of phase separation first occurred for some considerable pe riod, then it was followed by phase dissolution driven by chemical rea ction. The thermodegradative reaction of sPMMA triggered the dissoluti on process by probably forming PC/sPMMA graft or random copolymers at the interface, which eventually resulted in a single phase. However, a nnealing at elevated temperatures for an extended period could lead to cross-linking, and thus a two-phase structure could be fixed permanen tly. The early stage of spinodal decomposition was interpreted in term s of the linearized Cahn-Hilliard theory. In the late stages of spinod al decomposition, the relationship between scattering peak wavenumber and time was found to obey a power law, but the exponents showed a str ong dependence on temperature jumps. The temporal universal scaling fa iled due to the influence of the chemical reaction. (C) 1995 John Wile y & Sons, Inc.