Effects of sample preparation method on mixing and phase separation in binary polymer blends

Detailed studies of effects of sample preparation method on the kinetics of phase separation in a blend of polystyrene-co-maleic anhydride (SMA) with a commercial sample of polymethyl methacrylate containing ethyl acrylate as co-monomer (PMMAe) have been performed using light scattering techniques. Two preparation methods, viz. solution casting and melt mixing in a mini twin screw extruder were employed in this work. The blend, which shows lower critical solution temperature (LCST) behaviour, exhibits spinodal and binodal curves at higher temperatures in the case of solution casting than those from melt mixed samples. The relative values of the Cahn–Hilliard growth rate, R(q), obtained from the two preparation methods depend on blend concentration, R(q) being faster for solution cast samples at some concentrations and slower at others. Comparison of the data with recent theoretical developments for entangled polymer blends is reported.