COMPATIBILIZING EFFECT OF THERMOTROPIC LIQUID-CRYSTALLINE BLOCK-GRAFTCOPOLYMER ON LIQUID-CRYSTALLINE POLYCARBONATE POLYSTYRENE BLEND SYSTEMS

Thermotropic liquid crystalline (LC) block-graft copolymer (LCBG) comp osed of thermotropic LC polycarbonate (LCPC) in the backbone and polys tyrene (PS) segment in the side chain (reported previously) was added to incompatible polymer blend systems of thermotropic LCPC and commerc ial PS as a compatibilizer. The compatibility, morphology and mechanic al properties of the blends were evaluated by SEM, DSC and TMA measure ments. No compatibility between the LCPC and the PS was found in the L CPC-PS blend systems (LCPC:PS = 2:8) but the SEM examination indicated that fibrils were formed in the systems to which the LCBG was added. This finding means that the compatibility between LCPC and PS is impro ved. Data for glass transition steps by DSC measurements support this view. The blend system containing LCBG (5 wt%) showed the best mechani cal properties of all the systems. These results suggest that LCBG is a useful compatibilizer for the blend systems.