New Observation on Morphology of a Thermotropic Liquid Crystalline Polyesterimide Crystallized at High Temperature

The crystal morphology of a thermotropic liquid crystalline polyesterimide, derived from N, N′‐hexane‐1,6‐diylbis(trimellitimides), 4,4′‐dihydroxybenzophenone and p‐hydroxybenzoic acid, was investigated by means of polarized light microscopy (PLM) with a hot stage and scanning electron microscopy (SEM). The PLM observation indicates a series of phase transitions in the polyesterimide: with increasing temperature, the transformation from the amorphous state to nematic was observed at 264°C, followed by the conversion of nematic to isotropic melt at 290°C; crystallization in the isotropic phase occurred when the sample was maintained at 290°C on a glass substrate (only) for extended time. Very large and perfect Hedgehog spherulites were grown at 290°C with a fast growth rate. The SEM observation provided information on branching in crystals and spherulites impingement.

Keywords:

• crystal morphology
• polarized light microscopy
• phase transitions
• nematic state
• isotropic phase

Acknowledgment

The financial support of this study was provided by grants from Major Research Projects of Chinese National Nature Science Foundation (90103037) and Chinese National Nature Science Foundation (20474013), and by Ph.D. funds of the State Education Department of China. We are grateful to Dr. Phillip Geil (University of Illinois, USA) and Dr. Robert R. Luise (Hytem Consultants. Inc., USA) for their useful suggestions and comments.