Influence of annealing and casting solvent on the morphology of poly(ethylene oxide)-b-polystyrene-b-poly(ethylene oxide) triblock copolymer: compatibility effects

The influence of annealing on the morphology of solvent-cast films of poly(ethylene oxide)-b-polystyrene-b-poly(ethylene oxide) (PEO-b-PS-b-PEO) triblock copolymer was studied. The annealing temperature was chosen between the melting temperature of PEO and the glass transition temperature of PS. If the casting solvent is selective for PEO, microphase separation occurs and the crystallinity of the PEO is not affected by annealing. On the other hand, if the casting solvent is a good solvent for both blocks, a dramatic decrease in crystallinity of PEO is observed. This phenomenon is due to compatibility effects. The T g region of the PS-rich phase is shifted towards lower values. This behaviour was elucidated using differential scanning calorimetry combined with enthalpy relaxation experiments.