Miscibility as a function of copolymer composition in blends of a random copolymer and a homopolymer

Random copolymers ofn-butyl acrylate (BA) and cyclohexyl acrylate (CHA) were synthesized by solution polymerization in cyclohexane. Blends of polystyrene with the poly(CHA-stat-BA) copolymers were prepared by solvent casting and coprecipitation. The miscibility of the blends was characterized by means of differential scanning calorimetry. While blends with a low content of CHA in the copolymer showed two characteristic glass-transition temperatures of the corresponding blend components, those with a CHA content higher than 70% presented good compatibility. Phase separation of the miscible blends took place after annealing at 200 °C for 1 h, which implies an upper miscibility gap (lower critical solution temperature).