Abstract
In order to investigate relations between thermal behavior and microstructural properties of four thermotropic polysters, (1. X=Cl, 2. X=Br, 3. Y=Cl, 4. Y=Methyl), their thermal behavior was examined by differential scanning calorimetry on cooling from the anisotropic and isotropic melts of these polymers at a cooling rate of 20°C/min. Fracture surfaces of the polymers cooled from the isotropic and anisotropic melts in the DSC pan were observed by scanning electron microscopy. The polymers cooled from the anisotropic melt show crystallinity and have microstructures which are shaped like either ribbons or prisms. However, the crystallinity and the size of the microstructure are dependent upon the temperature at which the cooling of the polymers starts. The higher the temperature, the lower the crystallinity and the smaller the size of the microstructures. The transition of the anisotropic-isotropic melt of polymers 3 and 4 is observed on both heating and cooling. The polymers cooled from the isotropic melt show very low crystallinity, particularly polymer 3 is almost noncrystalline, and have uniformly fine structures. Microstructures formed on cooling from the isotropic melt are different from those formed on cooling from the anisotropic melt in the same way.
