CAS: Deconstructing Plastic and Agricultural Waste via Organosulfur Chemistry

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With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Rhett Smith of Clemson University will research ways to recycle agricultural and plastic waste, two underutilized and environmentally detrimental waste streams that represent critical barriers to a sustainable economy. The proposed research aims to benefit society by (1) elucidating new, sustainable ways to recycle plastic waste, (2) allowing access to sustainable products made from plant-derived material instead of from petroleum, and (3) alleviating environmental damage of plastic waste in the environment. This work will also benefit society through sustainability education. Resources on green and sustainable chemistry will be made available online where they may be accessed for free worldwide. This project will also help to improve participation in science, technology, engineering and mathematics degrees by engaging students from historically underserved and underrepresented groups.This work seeks to establish thio-cracking as a mechanism for chemical recycling/upcycling of plastic and agricultural waste. The thio-cracking approach being pursued involves the reaction of waste materials with elemental sulfur to yield organics and organosulfur compounds. Mixtures so derived are expected to be amenable to desulfurization to give new organic feedstocks. One aim of the research is to establish reactivity pathways between sulfur and functionalities found in target waste compounds including polyethylene terephthalate, polycarbonates, and lignin. These studies will involve the study of reactions of authentic waste materials and of small molecular model compounds. The anticipated reactivity will facilitate the formation of C–S bonds as sulfur will react with radical/radical-reactive species formed in the course of the thermal decomposition of organics at temperatures below 350 °C. This work aims to unveil fundamentally important mechanisms and microstructures resulting from C–S bond-formation and yield new organosulfur polymers. This work further seeks to provide one-pot protocols to convert plastics and biomass into new polymers and small molecular derivatives at significantly lower energy cost than required for many current chemical recycling strategies. This research has the potential to contribute to society by enabling waste reservoirs to be reclaimed for value-added applications, with this approach to recycling drawing upon the thermal reversibility of S–S bond formation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.