One-pot route to aryl halide/sulfur/olefin terpolymers via sequential crosslinking by radical-initiated aryl halide-sulfur polymerization, inverse vulcanization, and sulfenyl chloride formation

Abstract

High sulfur content materials (HSMs) are gaining attention as sustainable and versatile polymers due to their high sulfur content, low-cost feedstocks, and promising applications in energy storage, catalysis, sorbents, and structural composites. This work presents a sequential crosslinking strategy that combines three known sulfur–carbon bond-forming mechanisms—radical-initiated aryl halide sulfur polymerization (RASP), inverse vulcanization (InV), and sulfenyl chloride formation—to prepare high-performance HSM terpolymers. Specifically, elemental sulfur was first reacted with 2,4-dichloro-3,5-dimethylphenol (DDP) via RASP, forming polymer DS₈₁ and byproduct S₂Cl₂. Rather than discarding this toxic byproduct, O,O′-diallylbisphenol A (ABPA) was added to form sulfenyl chloride linkages in a single pot, yielding terpolymer DAClS₅₁. Control polymers DAS₅₀ (without S₂Cl₂) and AS₅₀ (via traditional InV) were also synthesized. A comprehensive suite of physicochemical analyses confirmed that sequential crosslinking allows remarkable property tuning and efficient byproduct valorization. Thermogravimetric analysis (TGA) showed that DAClS₅₁ and DAS₅₀ exhibit higher char yields (≥40 wt% at 800 °C) than single-step materials, underscoring the stabilizing effect of their crosslinked aromatic components. Differential scanning calorimetry (DSC) confirmed DAClS₅₁ had the highest glass transition temperature (36 °C), indicating increased crosslink density to the control polymers. SEM/EDX analysis confirmed uniform elemental distribution and residual chlorine in DAClS₅₁, verifying successful utilization of in situ S₂Cl₂. DAClS₅₁ also displayed the best mechanical properties, with flexural strength of 3.02 MPa and storage modulus of 357 MPa at 25 °C. This work showcases a potential route to synthesis HSMs by valorizing S₂Cl₂ and tuning properties via feedstock selection. It highlights the potential of integrated sulfur–carbon bond-forming strategies in sustainable polymer design and offers a pathway to address global sulfur surpluses through advanced material development.