Relationship between Crystallinity and Thermal Properties of Thermotropic Liquid Crystal Polyesters

Crystallinities of thermotropic liquid crystal polyesters (LCPs) were measured by X-ray diffraction. Crystallinities of LCPs estimated by Ruland's method, on the assumption that a glass state liquid crystal is equivalent to an amorphous state, had a good linear relation with their heat deflection temperatures. LCPs with higher crystallinity showed higher heat deflection temperature. An LCP with a bulky group on its backbone benzene ring exhibited extremely low crystallinity. The temperature dependence of its dynamic modulus was similar to that of a typical amorphous resin.