Synthesis of liquid crystalline block copolymer obtained by using main-chain polyurethane initiator and its thermal properties

A novel main-chain polyurethane initiator was obtained by the ternary polyaddition of mesogenic diol, aliphatic azodiol (initiator component), and diisocyanate. The mesogenic diol, in which 6-hydroxyhexyloxy groups linked to both sides of azobenzene, was synthesized. Subsequently, the novel liquid crystalline block copolymer, which has a multiblock structure consisting of alternately linked main-chain polyurethane and polymethacrylate units, was obtained by the radical polymerization of a methacrylate monomer (M11) having benzoic acid as the end group using the main-chain polyurethane initiator. The main-chain polyurethane initiator formed a nematic phase on the heating and cooling processes. Furthermore, the homopolymethacrylate (HPM11) obtained from M11 exhibited a smectic A phase. The main-chain polyurethane initiator could not be miscible with HPM11, and the phase separation was formed. However, the liquid crystalline block copolymer uniformly exhibited the nematic phase on the heating and cooling processes.