Aromatic polyesters obtained directly from hydroxybenzoic acids by hexachlorocyclotriphosphatriazene (PNC) in pyridine

Polyaryl esters of moderate molecular weights were prepared by the direct polycondensation reaction of hydroxybenzoic acids and its derivatives with hexachlorocyclotriphosphatriazene (also known as phosphonitrilic chloride trimer, PNC) as a condensing agent in pyridine. Copolymerization of p‐hydroxybenzoic acid with several hydroxybenzic acid derivatives was carried out to improve the processability of the polymer of p‐hydroxybenzoic acid, which yields fusible and soluble copolymers of high inherent viscosities. Polymer solubility and thermal behavior were examined.