Mesomorphic polyelectrolytes based on side-chain liquid-crystalline polymers containing end-on fixed mesogens and oligooxyethylenic spacers

Abstract

The synthesis and characterization of side-chain liquid-crystalline polysiloxanes based on 4′-cyanobiphenyl-4-yl 4-{2-[2-(2-allyloxyethoxy)ethoxy]ethoxy}benzoate (11a-3), 4′-cyanobiphenyl-4-yl 4-[2-(2-allyloxyethoxy)ethoxy]benzoate (11a-2), 4′-methoxybiphenyl-4yl 4-{2-[2-(2-allyloxyethoxy)ethoxy]ethoxy}benzoate (11b-3) and 4′methoxybiphenyl-4-yl 4-[2-(2-allyloxyethoxy)ethoxy]benzoate (11b-2) and of copolysiloxanes containing structural units derived from monomer 11a-2 and 2-(2-allyloxyethoxy)ethyl methyl ether (3-2), and from monomer 11a-3 and 2-[2-(2-allyloxyethoxy)ethoxy]ethyl methyl ether (3-3), are presented. The polysiloxanes based on 11a-3 and 11a-2 display an S_A mesophase, while the polysiloxanes based on 11b-3 and 11b-2 display N, and S_A and N mesomorphism, respectively. All copolysiloxanes display an S_A mesophase. The complexation of the polysiloxane based on the monomer 11a-3(i.e.P-11a-3) with LiCF₃SO₃ led to an increase in their glass-transition temperatures and a decrease in their S_A-I transition temperatures. These complexes are thermotropic liquid-crystalline polyelectrolytes which can accommodate up to 0.6 mol of salt per mole of ethylene oxide repeat unit (CH₂CH₂O).