The glass transition temperatures of homogeneous blends of polystyrene,poly(methyl methacrylate), and copolymers of styrene and methyl methacrylate

The glass transition temperatures T_g of homogeneous binary blends of the homo- and the statistical copolymers of the system poly(styrene-co-methyl methacrylate) were studied. Some of the blends, which are in the equilibrium phase separated, were forced into homogeneity. T_g (?) of the homopolymer blends (PS/PMMA)? follows the Fox equation, while T_g (x) of the pure copolymers P(S_xMMA_{1 ? x}) exhibits a minimum. This minimum can be effectively removed by blending the copolymers with small fractions (? ≈ 0,2) of one of the two homopolymers or a differently composed copolymer P(S_yMMA_{1 ? y}).