Disulfide-Induced Inhibition of Epoxy Cationic Photopolymerization: A Route to Maskless Patterning

In photoinduced cationic ring-opening polymerization (ROP) of epoxy monomers, chain-transfer reactions in the presence of alcohols are well established, and monosulfides are known to inhibit polymerization even at very low loadings (i.e., 0.01 mol%). Herein, it is thoroughly investigated the role of a disulfide-containing diol in quenching the polymerization of a difunctional epoxy formulation. Differently from the monosulfide, the propagation can start, and only at high sulfur:epoxy ratio the reactions of the disulfides with the oxonium ions effectively compete with the propagation and stops the polymerization. This inhibition mechanism can be exploited as a novel maskless photolithographic approach, enabling the spatially controlled patterning of epoxy coatings through localized deposition of the disulfide diol. As a proof of concept, sharply defined features with sizes down to 200 µm are successfully fabricated. These results introduce disulfide-mediated polymerization quenching as a versatile and material-efficient method for epoxy photopatterning.