Photoinduced inverse vulcanization

Abstract

The inverse vulcanization (IV) of elemental sulfur to generate sulfur-rich functional polymers has attracted much recent attention. However, the harsh reaction conditions required, even with metal catalysts, constrains the range of feasible crosslinkers. We report here a photoinduced IV that enables reaction at ambient temperatures, greatly broadening the scope for both substrates and products. These conditions enable volatile and gaseous alkenes and alkynes to be used in IV, leading to sustainable alternatives for environmentally harmful plastics that were hitherto inaccessible. Density functional theory calculations reveal different energy barriers for thermal, catalytic and photoinduced IV processes. This protocol circumvents the long curing times that are common in IV, generates no H₂S by-products, and produces high-molecular-weight polymers (up to 460,000 g mol^-1) with almost 100% atom economy. This photoinduced IV strategy advances both the fundamental chemistry of IV and its potential industrial application to generate materials from waste feedstocks.