Copolyphenyl esters were prepared from tere-/iso-phthaloyl chloride and bisphenol-A by interfacial polycondensation. The interfacial saponification reaction during the course of reaction and various factors affecting the molecular weight and yield have been investigated. Based on the experimental data

some problems in connection with the reaction mechanism are discussed. The composition (tere-/iso-) of the copolyester prepared under different reaction conditions were determined by means of infrared spectra.