Molecular Engineering of Liquid Crystal Polymers by Living Polymerization. 15.Molecular Design of Reentrant Nematic Mesophases in Binary Copolymers of omega-(4-cyano-4'-biphenyl)oxyAlkyl Vinyl Ethers

摘要

The reentrant nematic phase was discovered in 1975 in low molar mass liquidcrystals. Since then it received substantial theoretical and experimental interest. The first side chain liquid crystalline polymer exhibiting a nre phase was reported in 1986. This polymer was based on a polyacrylate backbone, six methylenic units in the flexible spacer, and 4-cyano-4'-oxybiphenyl side groups. In the mean time, several other polyacrylates containing mesogenic units with cyano groups and spacer lengths with five or six atoms were reported to exhibit the unusual i-n-SAd-nre sequence. So far, there are two copolymerization experiments with a monomer whose polymer exhibits a nre phase and a monomer whose polymer exhibits a n or SA mesophase.