Abstract
Summary: The successful incorporation of hydroquinone in thermal polyesterifications to prepare rigid linear copolyesters is hindered by the leaving group ability of phenols in nucleophilic acyl substitution reactions, the low nucleophilicity of phenols relative to aliphatic alcohols, and its volatility. To overcome these obstacles, with particular regard to improving the properties of poly(ethylene terephthalate), PET, we chose an approach whereby dyad‐based AB‐type mono(acetoxyphenyl) terephthalate monomers are transesterified into PET. In contrast to attempts to copolymerize terephthalic acid, ethylene glycol (EG) and hydroquinone, the transterification of small amounts (<10 mol‐%) of the preformed dyad in the absence of aliphatic diol, provides homogeneous random copolymers. Incorporation of larger amounts of aromatic diol gave only partly soluble materials. NMR analysis of the soluble fraction (in 20 vol.‐% TFA:CHCl~3~) indicated that the copolymers are substantially random. Transesterification of mono(4‐acetoxyphenyl) terephthalate (hydroquinone‐terephthalic acid, 1) and mono(3‐acetoxyphenyl) terephthalate (resorcinol‐terephthalic acid, 2) into PET allows us to further explore the effect of mesogen structure on the development of liquid crystalline copolyesters.
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