Transesterifications of poly(bisphenol A carbonate) with caprolactone segments in copolyester and poly(ε-caprolactone) homopolymer

Transesterification of poly(bisphenol A carbonate) with caprolactone segments in ethylene terephthalate–caprolactone copolyester was investigated using 1H and 1H–1H nuclear magnetic resonance (NMR) spectroscopy and a model compound. It was found that during annealing process, transesterification took place between poly(bisphenol A carbonate) and caprolactone segments and resulted in the formation of bisphenol A-caprolactone ester unit. On the basis of the results, we separately examined the interchange reaction of poly(bisphenol A carbonate) with poly(ε-caprolactone) homopolymer by 1H and 13C nuclear magnetic resonance spectroscopy. It was shown that in the presence of Ti compound catalyst, transesterification mainly occurred and gave rise to three different kinds of linkage patterns: bisphenol A-caprolactone ester unit, bisphenol A-caprolactone carbonate unit and caprolactone–caprolactone carbonate unit. However, the resultant aliphatic carbonate units were stable under the reaction conditions; the evidence of decarboxylation was not obtained from NMR measurements. The characteristics of the transesterification behavior will be discussed in this paper.