Direct polyesterification by use of phosphorus oxychloride and LiCl in pyridine

The reaction of the N‐phosphonium salt of pyridine derived from phosphorus oxychloride in pyridine was successfully used for the preparation of aromatic polyesters with high molecular weight when carried out in the presence of lithium chloride. In the copolycondensations of isophthalic and terephthalic acid with diphenols, the mode of reaction with the diacids was expected to produce several types of the diacid activated intermediates, which might control the sequences of the diacids in the copolymers. The possible variation of the sequences was studied in terms of the mode and copolymer properties such as glass transition temperatures and liquid crystalline transition temperatures. Competitive model reactions were carried out to discuss these relationships.