Crystallization kinetics of thermotropic liquid crystalline poly(ester-imide)s

Abstract

A thermotropic liquid crystalline poly(ester-imide) was synthesized from trimellitic anhydride, 5-aminovaleric acid and 2,6-dihydroxynaphthalene by the melt polymerization. The isothermal crystallization kinetics of the thermotropic liquid crystalline poly(ester-imide) was studied by using DSC in temperature range 190-240 degrees C. Crystallization occurs in two stages (a fast crystallization process and a slow crystallization process), leading to different levels of perfection and crystal sizes. The apparent Avrami exponent has the low values of 0.11-0.98, which represents a highly restricted one-dimensional (fibrillar) crystal growth. It tends to be depressed because the high ordered molecules (crystals) will prevent a polymer chain from the translational motion along the chain axis and the matching of crystallizable sequences with other chains. The fast crystallization process produces the relatively ordered crystals and the slow crystallization generates the less ordered crystals. WAXD shows that the dual endothermic peaks are related to the existence of two different crystal sizes. (C) 1997 Elsevier Science Ltd.