Abstract:

Inverse vulcanization shows great feasibility for the utilization and conversion of sulfur by-product into high-performance sulfur-rich polymers. However, its practical application is hindered by poorly inscrutable structural evolutions of products and thermodynamic instability. Herein, we develop a thioctic acid (TA)-initiated cascade polymerization strategy to synthesize thermoplastic polymers (SXTYDZ, where x, y, z represent the mass ratio of S8, TA, and DIB) with controllable structural evolution and enhanced mechanical properties for humid adhesion. The key to this TA-initiated ring-opening polymerization (ROP) of sulfur is to generate S radicals at 120 °C to produce short sulfur segments and avoid the chaotic S1D1 networks of traditional inverse vulcanization under elevated temperature. This short sulfur structural endows S?T?D? with exceptional toughness (2300% of strain at breaking) and hot-pressed S?T?D? with reinforced strength (11.64 MPa vs. 8.5 MPa baseline). The synergy of hydrophobic sulfur and benzene motifs and carboxyl-metal coordination bonds in S?T?D? ensures long-term adhesion stability (>130 days) under humid environments. We believe our work establishes a platform to reconcile the trade-off between structural control and performance in sulfur polymers, offering a scalable route to repurpose industrial sulfur waste into durable adhesives for harsh environments.