Molecular engineering of liquid crystal polymers by living polymerization

Summary This paper describes the synthesis of poly{11-[(4-cyano-4-biphenyl)oxy]undecanyl vinyl ether-co-2-[(4-cyano-4-biphenyl)oxy]ethyl vinyl ether} A/B {poly[(6-11)-co-(6-2)]A/B} where A/B refers to the molar ratio between the monomers 6-11 and 6-2, with number average molecular weights above 15, by living cationic polymerization. The phase behavior of the resulting copolymers was discussed as a function of copolymer composition. Within this range of molecular weights, in the first heating scan poly(6-11) exhibits a melting and an enantiotropic s_A phase, while poly(6-2) an inverse s_C phase. In the second and subsequent heating scans poly(6-11) displays an enantiotropic s_X (unidentified smectic phase) and a s_A mesophase, while poly(6-2) only a glass transition temperature. Depending on composition, poly[(6-11-co-6-2)]A/B either display an enantiotropic nematic, enantiotropic s_A or both enantiotropic nematic and anantiotropic s_A phases.