Polyamide synthesis by the direct polycondensation with phenylphosphonic dichloride in pyridine

The direct polycondensation of isophthalic acid (IPA) and aromatic diamines with a new phosphorus compound, phenylphosphonic dichloride (PPDC), was studied. PPDC could actually react with nearly a two molar amount of carboxyl groups, but more than 75 mol % PPDC with respect to the carboxyl groups of IPA were satisfactorily used in the polycondensation. The initial reaction of IPA with PPDC in pyridine at room temperature and then at 120°C was needed to complete the activation, and the subsequent aminolysis at 120°C for 3 h was most effective. The polyamides of high inherent viscosity were obtained even from weakly basic aromatic diamines, and their values were more than those obtained by the conventional method. In their thermal properties determined by the DTA, they showed Tgs and Tms higher than those reported before.