LIQUID-CRYSTALLINE BLOCK-COPOLYMERS BY SEQUENTIAL CATIONIC OR PROMOTED CATIONIC AND FREE-RADICAL POLYMERIZATIONS

The scope for the study of the synthesis and properties of liquid crys talline (LC) block copolymers is briefly outlined. While there are man y approaches to the synthesis of LC block copolymers, the use of azo m acroinitiators is very versatile and allows one to produce diverse blo ck copolymer architectures. Azo macroinitiators are prepared by cation ic or promoted cationic polymerization of tetrahydrofuran (1) or cyclo hexene oxide (2), and are then used to initiate the free-radical polym erization of various methacrylates 3, 4 or acrylates 5-9 containing me sogenic azobenzene or biphenyl units thereby yielding block copolymers . The AB or ABA block copolymers are microphase-separated and form sme ctic and/or nematic mesophases similar to the respective LC homopolyme rs.