Solvated Inverse vulcanisation by photopolymerisation

Abstract

Inverse Vulcanisation (IV) under neat reaction conditions (without solvent) has enabled the research and development of the fundamental chemistry as well as the generation of unique sulfur-rich polymers with unprecedented properties. However, such bulk polymerisation can be problematic, especially with high molecular weight. The energetics of the thermal polymerisation process, combined with poor heat control of solvent-free polymerisation, cause risks of dangerous auto-acceleration if the process is scaled up. The required high temperatures (>160 °C or 135 °C even with catalysts), exceed the boiling point of most commonplace organic solvents, preventing implementation of solvents for IV under thermal conditions. We report here a photo-induced IV polymerisation in solvent at room temperature. The reactions proceed smoothly and efficiently with excellent yields, despite the potential negative factors of reflection, refraction, and low absorption intensity of light by these organic solvents, opening an attractive avenue for the preparation of functional sulfur-rich polymers as well as their potential applications. The extension of crosslinkers to the value-added C5 fraction of industrial byproduct and β-carotene showcase the benefit of this low temperature protocol. Mechanistic study reveals that the moisture in both substrates and solvents might play a key role for the generation of toxic H2S by-product in IV reaction under thermal conditions, with photopolymerisation remaining un-affected. This protocol not only extensively expands the scope of crosslinkers for the IV reaction together with resultant polymers, but also provides a potential scale-up route for industrial application by avoiding the generation of toxic H2S by-product and possible explosion risk with high temperature.