Fully aromatic thermotropic liquid crystalline polyesters of 3‐phenyl‐4,4′‐biphenol with 4,4′‐benzophenone dicarboxylic acid

Abstract

AbstractA 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 (Tf) at 240°C, exhibited a nematic liquid crystalline phase, and had a narrow liquid crystalline range of 60°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‐naphthale‐nedicarboxylic acid (2,6‐NDA) and low Tf values in the range of 210–230°C, exhibited a nematic phase, and had accessible isotropization transitions (Ti) in the range of 320–420°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 (Tg) in the range of 167–190°C than those of other liquid crystalline polyesters, and excellent thermal stabilities (Td) in the range of 500–533°C, respectively. © 1995 John Wiley & Sons, Inc.