Thermally latent polyaddition and curing of Di- and tri-functional hemiacetal esters with diepoxide by salen-zinc complex with tunable catalytic activity and model and networking reactions

Abstract

Salen-zinc complexes (Zn/1R) thermal-latently catalyzed the polyaddition of a diepoxide (2) with a difunctional hemiacetal ester (3), which proceeded at moderate temperatures (100–150 °C) for curing of mixtures containing monomers and initiators. The catalytic activities of Zn/1R depended on the Lewis acidities of the complexes controlled by the electronic character of the salen ligands. For example, Zn/13,5-Cl bearing four electron-withdrawing chlorine atoms initiated the polyaddition at the lowest temperature (100 °C), and Zn/1OMe bearing two electron-donating methoxy groups initiated the polyaddition at 120 °C. The Lewis acidities of the complexes were evaluated by NMR and IR spectroscopies and computational calculation. The polyadditions with the salen-zinc complexes proceeded quantitatively at 150 °C, and the use of a tri-functional hemiacetal ester (7) with 2 afforded the corresponding networked polymer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1427–1439, 2008