Abstract
AbstractCopolyesters of 4‐hydroxybenzoic acid (HBA) and 3‐(4'‐hydroxyphenoxy)benzoic acid were prepared by two different procedures. Either the acetyl derivatives were polycondensed in bulk at temperatures up to 300°C or they were polycondensed in an inert reactions medium (Marlotherm‐S) at 340°C. Two analogous series of copolyesters were synthesized from 4‐acetoxybenzoic acid (4‐HBA) and 4‐(3'‐acetoxyphenoxy)benzoic acid. The copolyesters were characterized by elemental analyses, inherent viscosities, 1H‐ and 13C‐NMR spectroscopy, WAXS and DSC measurements, and by optical microscopy. All copolyesters synthesized in solution were highly crystalline materials which were neither meltable nor soluble. Part of the copolyesters prepared by polycondensation in bulk were semi‐crystalline, meltable, and soluble. The copolyester derived from 3‐(4'‐hydroxyphenoxy)benzoic acid proved to be thermotropic forming a nematic melt, whereas the isomeric copolyesters of 4‐(3'‐hydroxyphenoxy)benzoic acid only formed isotropic melts. © 1993 John Wiley & Sons, Inc.
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