Abstract
A series of multifunctional dithiocarbonates (DTCs) with a structural variety were synthesized from the corresponding multifunctional epoxy precursors, and their acceleration effects on the epoxy-amine curing system, which was consisted of bisphenol-A diglycidyl ether and amine-terminated poly (propylene glycol), were examined. As a result, all of the multifunctional DTCs exhibited excellent acceleration effects by virtue of the high reactivities of DTC with amine and that of the resulting thiol moiety with epoxide. The acceleration effects were not influenced by the number of DTC moieties in a molecule, but strongly influenced by the shapes of the multifunctional DTCs, i.e., the spatial distributions of the DTC groups around the core parts of the molecules. The highest acceleration effect would be achieved in the trifunctional DTC derived from triphenylolmethane triglycidyl ether. Molecular mechanics calculation (MM2) for this trifunctional DTC revealed that its inherently spread molecular structure permits the DTC moieties at the ends of the arms to be located apart from each other with maximizing the distances among them, which would be advantageous for their participation into the epoxy-amine curing system to promote the formation of a networked structure.
