During petroleum refinement, organosulfur compounds in crude oil are converted to elemental sulfur for storage. Despite millions of tons being produced annually, elemental sulfur has very few uses. Inverse vulcanization, developed by the Pyun group, repurposes this waste into polymers. Heating sulfur above 159 °C generates free radicals that bind to monomers, creating high sulfur content polysulfides. Only a subset of monomers has been explored utilizing inverse vulcanization. Here, compounds found in garlic such as diallyl sulfide (DAS) were used. They are challenging to polymerize using standard methods but react readily in the presence of elemental sulfur at 180 °C forming poly(S-DAS). Polymer formation was confirmed by <sup>1</sup>H-NMR. Initially, these polysulfides were viscous liquids. Once cured, the copolymer hardened allowing repurposed industrial waste and natural monomers to function as an adhesive. Characterization by gel permeation chromatography (GPC) and differential scanning calorimetry (DSC) revealed higher molecular weights and higher glass transition temperatures upon curing. Viscous polysulfides were applied to aluminum adherends, cured at 160 °C, and tested in shear. Despite the many benefits of inverse vulcanization, high reaction temperatures preclude the use of many monomers. Once in a linear arrangement, however, sulfur radicals can form at much lower temperatures (80-100 °C) allowing polymers formed by inverse vulcanization, such as poly(S-divinylbenzene), to act as initiators. This work uses poly(S-DVB) to polymerize, solvent free, a broader range of monomers with much lower boiling points using relatively mild temperatures. Additional monomers with vinyl and allyl functional groups were incorporated with boiling points as low as 94 °C. Copolymers were examined by NMR, GPC, and DSC. Utilizing different monomers led to changes in reaction times, and material properties. Modifications enabled tailoring of their metal binding capabilities. Inverse vulcanization offers a solvent free method to create functional materials from the repurposed petroleum waste product, sulfur.

Solvent-free formation of functional polymers by repurposing sulfur

255th National Meeting (2018)

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