Chemical modification of polymer main chain - A new path to liquid-crystalline polyesters with long siloxane segments. Significance of molecular mobility in the formation of the liquid-crystalline state

A new method for the synthesis of polymers incorporating dimethylsiloxane fragments of different length based on chemical modification of liquid‐crystalline poly[oxy(dimethylsilylene)‐methyleneoxycarbonyl‐1,4‐phenyleneoxyterephthaloyloxy‐1,4‐phenylenecarbonyloxymethylene‐(dimethylsilylene)] (polymer 1) is described. A series of thermotropic LC polymers 2 with extended dimethylsiloxane segments (up to 10 Si atoms per siloxane spacer) was synthesized by means of the reaction of prepolymer 1 with octamethylcyclotetrasiloxane in the presence of a sulfocation exchanger. Investigation of the dielectric properties of the polyesters 2 revealed that there exists a relationship between the ability of the polymers to form a mesophase and their molecular mobility parameters.