Miscibility of polymer blends of poly(styrene-co-4-hydroxystyrene) with bisphenol-A polycarbonate

The miscibility of blends of bisphenol-A polycarbonate (BAPC) and tetramethyl bisphenol-A polycarbonate (TMPC) with copolymers of poly(styrene-co-4-hydroxystyrene) (PSHS) was studied in this work. It has been demonstrated that BAPC is miscible with PSHS over a region of approximately 45-75 mol % hydroxyl groups in the copolymer. TMPC has a wider miscible window than BAPC when blended with PSHS. The blend miscibility was considered to be driven by the intermolecular attractive interactions between the hydroxyl groups of the PSHS and the p electrons of the aromatic rings of both polycarbonates (PCs). As the FTIR measurements showed, after blending of BAPC with PSHS, there is no visible shift of the carbonyl band of BAPC at 1774 cm^-1, whereas the stretching frequency of the free hydroxyl groups of the copolymers at 3523 cm^-1 disappeared. The large positive values of the segment interaction energy density parameter B_st-HS calculated from the group contribution approach indicated that the intramolecular repulsive interaction may also have played a role in the promotion of the blend miscibility.