Model reaction for thermally latent curing through addition of hemiacetal ester and epoxide by schiff‐base–zinc halide complexes

Abstract

AbstractSchiff‐base–zinc halide complexes (ZnX2/1) thermal‐latently catalyze the reaction of glycidyl phenyl ether (2) and 1‐propoxyethyl 2‐ethylhexanoate (3) that proceeds at moderately elevated temperatures. The catalysis by the ZnX2/1 complexes proceeds via the thermal dissociation of 3 to produce the corresponding carboxylic acid that nucleophilically attacks 2 predominantly over the thermally dissociated vinyl ether. ZnX2/1 complexes catalyze both the dissociation of 3 to produce the carboxylic acid intermediate and its addition to 2. Although conventional latent catalysts for this reaction exhibit Lewis acidities under ambient conditions that are responsible to the gradual degradation of hemiacetal esters and the polymerization of epoxides, a mixture of 2, 3, and ZnX2/1 can be stored for 3 months at ambient conditions. The stored mixture is as active as the freshly prepared mixture, keeping the excellent activity and latency of ZnX2/1. As well as the model reaction, the thermally latent polyaddition of bisphenol A diglycidyl ether (9) and di‐1‐propoxyethyl adipate (10) is also promoted with ZnCl2/1 at a moderate elevated temperature. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3370–3379, 2007