Hybrid thermotropic liquid‐crystalline block copolymers

Abstract

A new approach to the preparation of two classes of block copolymers containing liquid‐crystalline segments is reported. Copolymers 1 and 2 are constituted by polytetrahydrofuran and side‐chain liquid‐crystalline polymethacrylate blocks, whereas block copolymers 3 consist of polystyrene and main‐chain liquid‐crystalline polyester blocks. The synthetic procedures leading to copolymers 1‐3 are extremely versatile and can be used to prepare a great variety of block copolymer architectures. In both copolymer classes the chemically different blocks are strongly segregated in the solid and melt phases and undergo individual phase transitions. The mesophase transition temperatures of the liquid‐crystalline blocks are very similar to those of the corresponding homopolymers, and their enthalpies are directly proportional to the content of the liquid‐crystalline block.

Liquid crystalline block and graft copolymers

“…The interface was observed to be very well defined, about 2.5 f 1 nm thick. The same effect was observed for block copolymers with main chain components by Galli et al [57] (see Fig. Therefore, only a minor reduction of the A HcI compared to homopolymer has been recorded and attributed to the interface (see section size effects above) [52, 531. Similar results were reported by Finkelmann [33] and van der Velde [6 11.…”

“…Only statistical statements concerning the structure of the block copolymers can be made without extensive SEC investigations and a subsequent cleavage of the segmented block polymers in the individual polymer blocks [57]. However, the polymers obtained are insoluble in common organic solvents in most cases.…”

“…LC polyesters of different molecular weight which contain reactive azo groups were prepared by a polycondensation under phase transfer conditions [57,72,731. LC polyesters of different molecular weight which contain reactive azo groups were prepared by a polycondensation under phase transfer conditions [57,72,731.…”

“…10 in examples of main chain multi-block copolymers (LC polyesterPS) as described by Galli et al [57]. 10 in examples of main chain multi-block copolymers (LC polyesterPS) as described by Galli et al [57].…”

Synthesis of block and graft copolymers containing liquid-crystalline segments

“…The carboxylic acid function brings about these side reactions, which compete with the grafting reaction. This explains the rapid gel formation in entry (6). The use of tert-butyl ester instead of carboxylic acid function, as the site of grafting reaction, rather precludes gel formation.…”