Introducing a new electron acceptor for the implementation of photocyclic initiating system for radical photopolymerization

In this paper, a new kind of redox additive usable in photocyclic initiating systems for radical photopolymerization is presented. Di-toluene-4-sulfonamide is shown to act as a quite efficient candidate as electron acceptor due to its high reduction potential. Its effectiveness as an electron acceptor in UV to near-IR Type III photoinitiating systems for radical photopolymerization is demonstrated by interaction with three different dyes. Its implementation into type III photoinitiators leads to a two-fold enhancement of the polymerization rate. An exhaustive photochemical study is conducted giving a thorough description of the chemical reactions, demonstrating a photocatalytic cycle in the type III photoinitiating system for two of the dyes and the ability of the di-toluene-4-sulfonamide to enhance near IR sensitivity.