STEREOCOMPLEX FORMATION IN POLYBUTADIENE SYNDIOTACTIC POLY(METHYL METHACRYLATE) BLOCK COPOLYMERS BLENDED WITH ISOTACTIC POLY(METHYL METHACRYLATE)

The process of stereocomplexation in the bulk between isotactic poly(methyl methacrylate) and a polybutadiene-syndiotactic poly(methyl methacrylate) diblock copolymer was studied by differential scanning calorimetry as a function of composition of the blends, annealing time and temperature. The amount of complex formed is dependent on these three parameters, while the temperature of decomposition of the complex is only dependent on the temperature of annealing. One endotherm of decomposition was observed, in contrast to poly(methyl methacrylate) homopolymer blends, for which two endotherms referred to as T(m1) and T(m3) were generally reported. On the basis of a model proposed by Challa et al., the endotherm can be identified with T(m1). The absence of the second endotherm can be explained by the presence of the 'foreign' elastomer sequence preventing the formation of the lamellar crystals attributed to T(m3) in the model. For annealing temperatures larger than 140-degrees-C, no complex is formed.