Latency control of chemical reactions in polymerization of epoxy resins using a hydrogen bonding network

Abstract

Latency of chemical reactions is a crucial factor to control the physicochemical properties responsive to external stimuli such as light or heat. For example, when external triggers are applied to resin curing agents, curing reactions are required to be initiated instantly and uniformly. Latency is closely related to molecular architecture. In this study, we succeeded in controlling latency by tuning solubility of ionic liquid reagents in highly polar organic solvents by rational molecular packing design: implementation of a hydrogen bond network into the anion of the starting reagents raised the polymerization temperature because the solubility decreased. Because of the anion's hydrogen-bonding network, latency could be preserved even when a cation was replaced with less bulky ones. Theoretical analysis by DFT calculations supported the enhancement of latency induced by the implementation of a hydrogen bonding network in ionic liquid-type curing materials.