Polymers made by inverse vulcanization can be assembled, repaired, and recycled at room temperature through nucleophile-catalyzed S–S metathesis.

Sulfur is an underused by-product of the petrochemicals industry.R ecent research into inverse vulcanization has shown how this excesss ulfur can be transformed into functional polymers, by stabilization with organic crosslinkers. For these interesting new materials to realize their potential for applications,m ore understanding and control of their physical properties is needed. Here we report four new terpolymers prepared from sulfur and two distinct alkene monomers that can be predictively tuned in glass transition, molecular weight, solubility,m echanical properties, and color.

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Inverse vulcanization provides dynamic and responsive materials made from elemental sulfur and unsaturated cross-linkers. These polymers have been used in av ariety of applicationss uch as energy storage, infrared optics, repairable materials, environmental remediation, and precision fertilizers. In spite of thesea dvances, there is an eed for methods to recycle and reprocess these polymers. In this study,p olymers prepared by inverse vulcanization are shown to undergo reactive compression molding. In this process, the reactive interfaces of sulfur polymers are brought into contact by mechanicalc ompression.U pon heating these molds at relatively low temperatures (% 100 8C), chemical bonding occurs at the polymer interfaces by SÀSm etathesis. This method of processing is distinct from previouss tudies on inverse vulcanization because the polymers examined in this study do not form al iquid phase when heated. Neither compression nor heatinga lone was sufficient to mold these polymers into new architectures, so this is an ew concept in the manipulation of sulfur polymers. Additionally,h igh-level ab initio calculations revealed that the weakest SÀSb ond in organic polysulfides decreases linearly in strength from as ulfur rank of 2t o4 ,b ut then remains constant at about 100kJmol À1 for highers ulfur rank. This is criticali nformation in engineering these polymers for SÀSm etathesis. Guidedb yt his insight, polymer repair,r ecycling, and repurposingi nto new composites was demonstrated.

Apolysulfide material was synthesized by the direct reaction of sulfur and d-limonene,b y-products of the petroleum and citrus industries,r espectively.T he resulting material was processed into functional coatings or molded into solid devices for the removal of palladium and mercury salts from water and soil. The binding of mercury(II) to the sulfurlimonene polysulfide resulted in acolor change.These properties motivate application in next-generation environmental remediation and mercury sensing.The exploration of sustainable feedstocks is important in the synthesis of functional materials.[1] Herein, we report the utility of apolysulfide synthesized directly from two industrial by-products:s ulfur [2] and d-limonene [3] (Scheme 1). This study was inspired by classic reports on the reaction of sulfur and limonene, [4] theu se of limonene as ar enewable monomer, [5] and the recent and innovative applications of "inverse vulcanization" to access av ariety of advanced materials with high sulfur content. [6] We found that the sulfur-limonene polysulfide can be processed into coatings and solid devices that remove metal salts such as palladium-(II) and mercury(II) from water and soil. We also report the discovery of ac hromogenic response when the polysulfide is exposed to mercury(II). As sulfur is produced annually in excess of 60 million tons as ab y-product of petroleum refining [2] and more than 70 thousand tons of limonene are isolated each year from orange zest in the citrus industry, [3] the sulfur-limonene polysulfide is inexpensive-further motivating its use in metal sequestration, sensing,and environmental remediation.As as tarting point, sulfur was melted (T > 120 8 8C) and then heated to 170 8 8C. Above 150 8 8C, SÀSb ond scission occurs, [7] thereby generating thiyl radicals that could add to limonene.A ne qual mass of limonene was added to the molten sulfur,w hich produced at wo-phase mixture that becomes as ingle,d ark red phase upon reaction. An equal mass of sulfur and limonene was chosen to maximize the content of both industrial by-products in the final material. 1 HNMR analysis of the reaction mixture indicated limonenes exocyclic alkene was consumed more rapidly than its endocyclic alkene,w ith complete consumption of all olefins within 90 min (see Figures S6-S8 in the Supporting Information). Little change was observed by 1 HNMR spectroscopy on further heating. Scheme 1. Synthesis and applicationso fasulfur-limonene polysulfide.