Highly aromatic liquid crystalline copolyesters synthesized by transesterification of poly(ethylene terephthalate) with acetoxybenzoic acid, diacetoxybenzene and terephthalic acid

New liquid-crystalline copolyesters have been synthesized by the melt transesterification of poly(ethylene terephthalate) (p(ET)) with 4-acetoxybenzoic acid (H), and varying proportions of equimolar mixtures of diacetylated hydroquinone (Q) and terephthalic acid (T). It has been shown that the risk of solidification of the reaction mixture due to segregation of a high melting phase formed by polymer chains rich in aromatic units is appreciably lowered with respect to systems where only H is reacted with p(ET). Moreover, the addition of appropriate amounts of Q and T (5-30%, with respect to H) has been shown to improve the polymers homogeneity. Thus, p(ETHQ) copolyesters with processability characteristics comparable to those of commercial p(ETH) copolyesters can be prepared with a considerably higher content of aromatic units, with a beneficial effect on mechanical properties and temperature resistance.