Base-Catalyzed Thiol-Epoxy Reactions: Energetic and Kinetic Evaluations

Abstract

The mechanism of the base-catalyzed thiol-epoxide stage of the thiol-ene/thiol-epoxide curing process was investigated using quantum chemical tools. This study searched for conventional tertiary amines with low to medium basicity as initiators to control reaction rates and tailor industrial applications. Challenges arise from the stronger basicity of initiators, leading to an uncontrollable and short curing application period. This problem was put into quantitative data through kinetic and energetic studies for the first time. Furthermore, the base catalyst formulation of curing agents distinctively has a short pot life. More reactivity of terminal epoxy rings than internal ones was highlighted for the curing agents. It was revealed that the reactivity augments during the curing process while environmental polarity changes from higher to lower, which is one of the reasons that triggers an autocatalytic phenomenon. Electronegative atoms like fluorine on thiols significantly decrease the nucleophilicity of formed thiolate anion, enabling longer curing application.