ORDERED STRUCTURES IN A SERIES OF LIQUID-CRYSTALLINE POLY(ESTER IMIDE)S

A series of poly(ester imide)s (PEIMs) has been synthesized from -(chl oroformyl)phenyl]-4-(chloroformyl)phthalimide and different diols with methylene units of 4 to 12 (n). PEIMs with both even and odd methylen e units exhibit a monotropic mesophase behavior during cooling due to the supercooling necessary for crystallization. Identification of this mesophase as a monotropic liquid crystal with smectic A order has bee n carried out via differential scanning calorimetry, wide angle X-ray diffraction (WAXD), small angle X-ray scattering, polarized light micr oscopy, and transmission electron microscopy. It is found that the met hylene units in these chain molecules are also largely responsible for the formation of this liquid crystal phase. After investigating diffe rent types of main chain mesogen-nonmesogen liquid crystal polymers, a general concept considering the contributions to enthalpy and entropy changes during the liquid crystal transitions may be associated with the relative rigidity, linearity, and regularity of the mesogenic grou ps compared to the methylene units. Detailed WAXD study of fiber and p owder patterns indicates that the degree of orientation and the order correlation lengths along and perpendicular to the direction of chain molecules (chain lateral packing and layer structure) not only increas e with the number of methylene units but also show an even-odd alterna tion. A possible chain packing model is suggested. The morphology and defects of this smectic A liquid crystal phase are also discussed.