Synthesis and characterization of a series of wholly aromatic copolyesterscontaining 2-(alpha-phenylisopropyl) hydroquinone moiety

Two series of new wholly aromatic thermotropic copolyesters containing the 2-(alpha-phenylisopropyl)hydroquinone (PIHQ) moiety have been synthesized a nd their basic properties such as glass transition temperature (T-g), melti ng temperature (T-m), thermal stability, crystallinity, and liquid crystall inity were studied by differential scanning calorimetry (DSC), thermogravim etry (TG), and wide-angle X-ray diffractometry (WAXD) and on a polarizing m icroscope. The first series was prepared from acetylated PIHQ, terephthalic acid (TPA), and 2,6-naphthalenedicarboxylic acid (NDA), and the second ser ies from acetylated PIHQ, TPA, and 1,1'-biphenyl-4,4'-dicarboxylic acid (BD A). The T-g values (152-168 degrees C) of the two series are not much diffe rent, although the values for the first series appear slightly higher. The T-m values (287-378 degrees C) and the degree of crystallinity of the first series are appreciably greater than those of the second series. Such diffe rences can be explained by the geometric structure of NDA and BDA moieties. All of the present polyesters are thermotropic and nematic. (C) 1999 John Wiley & Sons, Inc.