HYBRID THERMOTROPIC LIQUID-CRYSTALLINE BLOCK-COPOLYMERS

A new approach to the preparation of two classes of block copolymers c ontaining liquid-crystalline segments is reported. Copolymers 1 and 2 are constituted by polytetrahydrofuran and side-chain liquid-crystalli ne polymethacrylate blocks, whereas block copolymers 3 consist of poly styrene and main-chain liquid-crystalline polyester blocks. The synthe tic procedures leading to copolymers 1-3 are extremely versatile and c an be used to prepare a great variety of block copolymer architectures . In both copolymer classes the chemically different blocks are strong ly segregated in the solid and melt phases and undergo individual phas e transitions. The mesophase transition temperatures of the liquid-cry stalline blocks are very similar to those of the corresponding homopol ymers, and their enthalpies are directly proportional to the content o f the liquid-crystalline block.