Synthesis and characterization of side chain liquid crystalline polymers with a polythiophene backbone

Abstract

Poly{3-(4-Methoxy-4-hexyloxybiphenyl)oxymethylthiophene} (PolyMHOT), poly{3-(4-cyano-4-hexyloxybiphenyl) oxymethylthiophene} (PolyCHOT), and poly{3-[2-(2(2-(4-methoxybiphenyl)ethoxy)ethoxy)-ethoxy]methylthiophene} (PolyMEET) have been prepared to examine the effect of liquid crystalline properties on the conducting polymer structure. Thiophene derivatives with different mesogenic and spacer groups were synthesized by modified Williamson ether synthesis. These monomers exhibited enantiotropic smectic liquid crystalline mesophase. Polymerization was carried out by chemical and electrochemical methods. In chemical method, polymer yields were quite high and the polymerization required 3 eq. of oxidant to monomer. In the electrochemical procedure, the monomers exhibit an anodic peak due to the formation of radical cation with onset potential about 1.10 V and form electroactive polymer film. These polymers, however, were insoluble organic solvents and not observed liquid crystalline properties due to small portion of crosslinked polymer structure and inherently rigid polythiophene backbone.