EFFECTS OF SEQUENCE LENGTH DISTRIBUTION ON HEAT-CAPACITY AND GLASS-TRANSITION TEMPERATURE OF STYRENE-METHYL METHACRYLATE COPOLYMERS

Heat capacities of alternating, statistical and diblock copolymers of styrene and methyl methacrylate were measured with a differential scan ning calorimeter from 200 to 450 K to examine the additivity of heat c apacity. In both solid and liquid regions, the heat capacity was found to be additive, in most cases within +/- 2% error irrespective of seq uence length distribution. The glass transition temperatures, determin ed from enthalpy-temperature plots, depended on sequence length distri bution as well as composition. This behaviour, although theoretically expected, was found to be complicated by another factor, tacticity.