FULLY AROMATIC THERMOTROPIC LIQUID-CRYSTALLINE POLYESTERS OF 3-PHENYL-4,4'-BIPHENOL WITH 4,4'-BENZOPHENONE DICARBOXYLIC-ACID

A series of fully aromatic, thermotropic polyesters, derived from 3-phenyl-4,4'-biphenol (MPBP), nonlinear 4,4'-benzophenone dicarboxylic acid (4,4'-BDA), and various other comonomers was prepared by the melt polycondensation method and characterized for their thermotropic liquid crystalline behavior by a variety of experimental techniques. The homopolymer of MPBP with 4,4'-BDA had a fusion temperature (T-f) at 240 degrees C, exhibited a nematic liquid crystalline phase, and had a narrow liquid crystalline range of 60 degrees C. All of the copolyesters of MPBP with 4,4'-BDA and either 30 mol % 4-hydroxybenzoic acid (HBA), 6-hydroxy-2-naphthoic acid (HNA) or 50 mol % terephthalic acid (TA), 2,6-naphthalenedicarboxylic acid (2,6-NDA) and low T-f values in the range of 210-230 degrees C, exhibited a nematic phase, and had accessible isotropization transitions (T-i) in the range of 320-420 degrees C, respectively. As expected, each of them had a broader range of liquid crystalline phase than the homopolymer. They had a ''frozen'' nematic, glassy order as determined with the wide-angle X-ray diffraction (WAXD) studies. The morphology of each of the ''as-made'' polyesters had a fibrous structure as determined with the scanning electron microscopy (SEM), which arises because of the liquid crystalline domains. Moreover, they had higher glass transition temperatures (T-g) in the range of 167-190 degrees C than those of other liquid crystalline polyesters, and excellent thermal stabilities (T-d) in the range of 500-533 degrees C, respectively. (C) 1995 John Wiley and Sons, Inc.