Photocatalytic Disulfide Bond Coupling by Surface-Reduced Manganese Oxide for Controlled Polysulfide-Based Polymer Synthesis

Manganese oxide (MnO2) is a commonly used vulcanizing agent, which can convert polysulfide oligomers with reactive terminal mercaptans into polymeric networks. Herein, an elegant approach for the fast and facile curing behavior of polysulfide rubbers was disclosed under visible-light irradiation. Photocatalytic disulfide bond coupling of mercaptan end groups can be achieved on MnO2 in the presence of visible-light irradiation. More importantly, compared with pristine MnO2, surface-reduced MnO2 (R-MnO2) with abundant Mn3+ sites and oxygen vacancies exhibited superior vulcanizing performance. Theoretical simulation uncovers that R-MnO2 can facilitate electron transfer due to a narrowed energy band gap and reduce the energy barriers required for photocatalytic disulfide bond formation. This work opens up the potential of using visible light together with surface modification to tune the vulcanizing process and the properties of polysulfide rubbers.