Liquid Crystal Polymers: 16 Polar Substituent Effects on Thermotropic Properties of Aromatic Polyesters

Summary

A series of polyesters containing monosubstituted p-phenylene bis-terephthalate mesogenic groups and decamethylene flexible spacers was prepared and characterized for the effect of substituent polarity and size on the transition temperatures and on the thermal stability and type of liquid crystalline phase formed. No simple correlation between the polar effects of the lateral substituents and the thermal stabilities of the polymer mesophases was observed. The polar effects of the substituents appeared to be less important than their steric effects in controlling the thermotropic transitions of these polymers and of essentially no importance in controlling their glass temperatures and melting points. Optical textures of the polymer melts did not provide clear conclusions as to the nature of the liquid crystalline phases formed by these polymers, but their textures resembled those of low molecular weight nematics.