MISCIBILITY IN BLENDS OF LIQUID-CRYSTALLINE POLY(P-OXYBENZOATE-CO-P-PHENYLENEISOPHTHALATE) AND POLYCARBONATE

The miscibility of liquid crystalline poly(p-oxybenzoate-co-p-phenylen eisophthalate) (HIQ) and polycarbonate (PC) was investigated with diff erential scanning calorimetry (d.s.c.). It was found that blends of li quid crystalline HIQ and PC showed a single glass transition temperatu re across the whole composition range. Annealing these blends at tempe ratures slightly above the melting point of HIQ, ester exchange occurr ed as confirmed both by i.r. and n.m.r. spectroscopy. The apparent mis cibility of HIQ and PC was caused by this reaction. The blends retaine d liquid crystalline characteristics in the first few reaction minutes . As the transesterification continued, the bisphenol-A segment in PC reacted with both isophthalate and oxybenzoate segments in HIQ. This r esulted in amorphous polymers. These amorphous polymers exhibited a si ngle glass transition temperature higher than that for both pure polym ers. (C) 1997 Elsevier Science Ltd.