Sulfur-based polymers by inverse vulcanization: a novel path to foster green chemistry

The world is witnessing a growing interest in the utilization of waste materials to reduce environmental burden, add product value and promote sustainability. Such noble goals are being supported by the implementation of a number of approaches, including green chemistry. Currently, accumulation of large amounts of waste elemental sulfur, a by-product produced in gas and petroleum refineries, is posing an environmental concern and requires immediate intervention to search for new routes to make high-value materials from it. Inverse vulcanization is a new copolymerization technique allowing formation of stable sulfur-based polymers (sulfur copolymers) against the depolymerization of sulfur chains. Such a new class of polymers has demonstrated great properties for several environmental and renewable-energy applications. This paper reviews the advances in the evolution of sulfur copolymers prepared by inverse vulcanization with various monomers, including not only petro-based monomers but also renewable monomers as well as vegetable oils. Several applications of the obtained sulfur-based polymers are discussed. The challenges and future research directions to develop new polymers further and extend their applications are elaborated.