Synthesis and characterization of poly(vinylether)s with pendant mesogenic groups

Two different methods of synthesis were examined for the preparation of poly(alkylvinylether)s with pendant 4-cyano-4-oxy-biphenyl mesogenic groups attached to side chains of different length: a) anchoring of the mesogenic group onto an alkylvinylether monomer followed by polymerization or b) synthesis of the corresponding poly(chloroalkylvinylether)s and chemical substitution of the pendant chlorine by the mesogenic groups. Polymerization were performed with initiating systems based on activated iodide. Much better control of MW and MWD of the final polyvinylether chains was obtained when process b) was applied. Polymers with 2 and 4 carbons in the spacer do not show liquid crystalline properties. It is only with polymers having six carbon atoms in the spacer that mesophases were observed. Those issued from process b) give two distinct mesophases: a smectic A phase in the high temperature range and a smectic C phase for the low one. Polymers synthetized from process a) present only the smectic A phase. The effects of molecular weights and molecular weight distributions on the liquid crystalline properties have been examined and are discussed.