Differential scanning calorimetry (DSC) measurements of glass transition temperature (T-g) and of changes in heat capacity at T-g have been made on a series of electro-optically active alternating block copolymers of systematically varying hard and soft block structures and of their blends with the plasticizer, 1,12-dibromododecane (DBDD) in order to assess the nature of phase separation in these copolymers.