Purpose-driven polymers: Mechanistic insights and empirical advances in inverse vulcanized polysulfides for mercury remediation

Inverse vulcanized polysulfides (IV PS) are an emerging class of sulfur-rich polymers that have garnered increasing attention as promising adsorbents for mercury (Hg) remediation. Their chemical tunability, abundance of soft Lewis base sulfur moieties, and alignment with green chemistry principles position them as potentially sustainable and cost-effective solutions for addressing Hg, one of the most toxic and persistent pollutants. This promise is further reinforced by their green credentials: IV PS are synthesized from elemental sulfur, an abundant industrial by-product, often in combination with renewable monomers, enabling sustainable, high-capacity sorbents with low production cost. Yet, a critical question remains: have IV PS truly delivered on their potential as ideal Hg adsorbents? This review explores the purpose-driven development of IV PS-based Hg adsorbents, spanning foundational synthesis strategies to emerging computational approaches. Key motivations discussed include: (1) comonomer selection; (2) enhancement of adsorbent properties (e.g., surface area, wettability, reactivity, and topology); (3) advances in inverse vulcanization strategies (e.g., catalyst-free multicomponent polymerization/nucleophilic activation and catalysis); (4) performance evaluation; and (5) integration of computational tools. Addressing whether IV PS have reached their potential, this review critically examines performance metrics (i.e., adsorption isotherms, kinetics, selectivity, and cost-effectiveness) underscoring the need for standardized performance testing reporting and introduces the concept of percent binding site utilization to better leverage their high sulfur content. By identifying critical gaps in design development and performance evaluation of IV PS, this review provides a foundation for advancing IV PS from promising laboratory materials to practical, scalable solutions for Hg remediation.