Mechanically Tunable and Optically Exceptional Polysulfide Elastomers via Thioctic Acid-Mediated Inverse Vulcanization

Using industrial byproduct sulfur (S 8 ) as a feedstock to produce sulfur-rich polymers is a dual-benefit strategy that both addresses environmental concerns and unlocks intriguing material properties endowed by high sulfur content. Inverse vulcanization is an attractive approach to access sulfur-rich polymers; yet persistent challenges including limited structural control, ambiguous structure–property relationships, and poor mechanical performance have impeded their practical applications. Herein, we synthesized a series of polysulfide elastomers (STC) via one-pot, catalyst-free ternary copolymerization of S 8, thioctic acid (TA), and triallyl isocyanurate (TAIC) under mild conditions. The terpolymerization proceeds via a cascade mechanism: initial ring-opening of TA generates thiyl radicals, which initiate the ring-opening polymerization of S 8; the ensuing polysulfide radicals then react with TAIC to forge cross-linked networks. The three comonomers are judiciously integrated to fulfill distinct yet synergistic functions. By systematically varying monomer feed ratios, the cross-linking density and chain flexibility of the resulting networks are precisely regulated, enabling versatile tunability of thermomechanical and dynamic properties. Dynamic S–S bonds endow STC elastomers with both mechanical and chemical recyclability. Remarkably, STC elastomers exhibit an exceptional combination of high refractive indices, high Abbe numbers, and excellent near-infrared transmittance. These distinctive features, together with their elastomeric nature and dynamic reversibility, position them as promising candidates for flexible, healable, and recycled optical lens applications.