Morphology and phase separation kinetics of a compatibilized blend

The phase diagram for a low molecular weight blend of deuterated polystyrene (PSD, M(w) = 1000 g/mol) and polybutadiene (PB, M(w) = 5100 g/mol) was determined by light scattering measurements. The critical temperature of the blend was 51 degrees C and the critical composition was approximately 0.75 g/g polystyrene (75% PSD by weight). Upon addition of a PSD-PB diblock copolymer (total M(w) = 10,600 g/mol) near the critical composition, the phase boundary shifted linearly to a lower temperature and the rate of phase separation was greatly retarded. The size scale of the phase separated microstructure was also greatly reduced as block copolymer was added, indicating compatibilization of the blend.