Renewable sulfur- and monoterpenes-derived polysulfides as functional crosslinker for epoxy thermosets

Polymer materials, with sulfur as the major part of the backbone structure, are gaining increasing importance because of the large abundance of sulfur and the unique features of polysulfide linkages for modifying material properties. Herein, we introduce polysulfides, which are synthesized from sulfur and monoterpenes, as poly-thiols platform for the crosslinking of epoxy, allowing flexible sulfur constituents incorporate into covalently linked networks. This synthesis can be conducted in a simple, mild, and practical one-pot procedure proceed smoothly in a solvent-free manner with high sulfur utilization to afford sulfur–monoterpene polysulfides (PST) with high sulfur content (up to 58%) and good solubility. The epoxy was cured with PST with imidazole as the catalyst, producing highly sulfur crosslinked thermosets, which is supposed to proceed via a thiol-epoxy reaction mechanism. The resulting thermoset perform good toughness, high transmittance and potential self-healing ability.