Branching of High Molecular Weight Polyhydroxyethers Based on Bisphenol-A

Abstract

The kinetics of the polyaddition reaction of diglycidyl ether of Bisphenol A with Bisphenol A in solution and in the melt has been studied using tetrabutyl ammonium hydroxide and benzyl triethyl ammonium chloride as catalysts at several temperatures. The weight average molecular weight (Mw) and the number average molecular weight (Mn) can be related to the extents of reaction of the phenolic hydroxyl groups (α), the epoxide groups (β) and the branching probability p using a statistical method based on the cascade theory of branching processes. p is defined as the number of branches per secondary hydroxyl group in the chain. From p a kinetic parameter, b = k2/k1, can be determined, where k2 is the rate constant for the addition of epoxide to the secondary hydroxyl groups in the chain (the chain branching step), and k1 the rate constant for the addition of epoxide to the phenolic hydroxyl groups (the chain lengthening step). From the kinetic and molecular weight data, it has been possible to calculate b. The application of the branching theory and the measurements of the kinetics of the reaction are of considerable practical importance, as it enables the rational selection of catalysts, and allows the prediction of suitable reaction conditions for the synthesis of high molecular weight phenoxy resins.