Model studies on the kinetics and mechanism of polyarylate synthesis by acidolysis

Abstract

AbstractModel reactions were carried out to simulate the acidolysis process for polyarylate synthesis by using p‐tert‐butylphenyl acetate (ptBuPhOAc) and benzoic acid in diphenyl ether. p‐tert‐Butylphenol was formed in the reaction mixture and its concentration stayed constant throughout the reaction. Acetic benzoic anhydride and benzoic anhydride were detected by NMR. Based on this experimental evidence, a mechanism for the acidolysis was proposed involving the mixed anhydride. The kinetics of the acidolysis reaction was studied for this model reaction. The overall reaction order is two and the reaction order with respect to each reactant is one. Second‐order reaction rate constants were measured at different reaction conditions (200–250°C). The activation energy (Ea), activation enthalpy (ΔH≠), and activation entropy (ΔS≠) were calculated from these data. The thermodynamic parameters of the acidolysis reaction were also measured for the analogous reaction of p‐tert‐butylphenyl pivalate (ptBuPhOPiv) and benzoic acid. The kinetics of two other elementary reactions involved in the acidolysis reaction were also studied: p‐tert‐butylphenol with acetic anhydride or benzoic anhydride, and p‐tert‐butylphenyl pivalate with benzoic acid.