Recyclable Thermoset Enabled by Copolymer of Elemental Sulfur and Acrylate With Controlled Disulfide Linkages

Thermoset polymers have found a number of applications. However, their recycling faces a challenge due to their chemically crosslinked structure, which brings environmental pollution. Introduction of dynamic disulfide linkages can overcome this obstacle in principle. Yet, the disulfide compounds used to build the dynamic bonds are very limited and expensive, making their practical applications rather difficult. In this study, we present copolymer of elemental sulfur (S₈) and acrylate with controlled disulfide linkages synthesized via anionic hybrid copolymerization (AHCP). Such a copolymer can serve as a curing agent for conventional thermosetting resins including epoxy, polyurethane, and unsaturated polyester. The resulting thermoset demonstrates remarkable reprocessability, retaining over 86% of its maximum stress and strain at break after five cycles of processing at 120°C and pressure of 10 MPa. It also exhibits strong UV-blocking capability with zero transmittance in the ultraviolet range. Particularly, the thermoset is recyclable. Namely, it can degrade into oligomers in the presence of S₈, which can be reused as curing agents for new thermosets or directly employed as robust adhesives for diverse substrates. The precise synthesis of polymer with controlled disulfide linkages provides a platform to transform conventional thermosets into high-performance recyclable materials.