Enthalpy Relaxations in Blends of Polystyrene and Poly(2-vinylpyridine)

An earlier proposed enthalpy relaxation method for investigating miscibility in blends of polymers with a similar glass transition temperature (Tg) is applied to mixtures of polystyrene (PS) and poly(2-vinylpyridine) (P2VP). Both polymers are k nown to be immiscible, but despite the fact that the respective Tgs are 6 °C apart, only a single specific heat jump is visible in a conventional differentional scanning calorimetry (DSC) experiment. Physical aging at suitable temperature gives rise to two clearly separated enthalpy recovery peaks in the first DSC scan, thereby demonstrating the two-phase morphology. These experiments together with theoretical considerations based on Moynihan's approach will be used to formulate conditions for a successful application of the enthalpy relaxation method.