Compatibility of polystyrene and poly(methyl methacrylate) in benzene. Effects of molecular weight and temperature

The incompatibility of polystyrene and poly(methyl methacrylate) in benzene was examined at 20.1°, 40.0°, and 60.2°C. The incipient cloud points of solutions of equal weights of the two polymers were determined by a novel photometric method. Polystyrene samples with weight‐average molecular weights in the range of 3.27 × 10 5 to 6.43 × 10 4 and poly(methyl methacrylate) samples with weight‐average molecular weights in the range of 8.97 × 10 5 to 8.76 × 10 4 were used. Models describing the dependence on molecular weight of the critical concentration of a ternary polymer–polymer–solvent system, presented by Fuchs and by Kuhn et al., were examined in light of the experimental data. A modified model is proposed which gives an improved correlation of these results.