EFRI E3P: CAS: Transformative Upcycling of Polymers by Activating Chemistries

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This project envisions a transformative “upcycling” of common end-of-life plastics (ELPs) by depolymerization (i.e., deconstruction) mechanisms that are achieved using “activating” chemistries. These activating chemistries are straightforward, scalable chemical reactions that modify the waste polymers such that the subsequent depolymerization products are much more valuable and useful than products obtained through conventional recycling or established depolymerization chemistries. This project focuses on enabling depolymerization and upcycling of two of the most difficult to recycle polymers - poly(vinyl chloride) (PVC) and polyurethane (PU) materials. The global demand for PVC and PU products continues to grow despite the lack of any viable recycling methods for these materials. This project will develop novel methods for converting waste PVC to small molecules that have existing uses as chemical intermediates, consumer products, solvents, and other end-uses. Similarly, polyurethane (PU) materials will be broken down into more valuable molecules via reactions that yield carbon-carbon double bonds in the final products. Oligomers (the products of partial depolymerization) derived from PVC and poly(ethylene terephthalate) (PET) will be used to form thermoplastic elastomers (TPEs). Unlike thermoset elastomers, TPEs can be melted, molded, reprocessed, are potentially easier to recycle, and are much more valuable than typical thermoset elastomers and plastics. The project provides highly interdisciplinary research training for graduate and undergraduate students and creates an annual summer immersion experience for high school students in Tuscaloosa, AL. The summer immersion experience is expected to instill a personal investment in helping to eliminate ELPs from the environment and to explore the students’ interest in pursuing engineering as a career. A synergistic activity for high school students aligned with the American Chemical Society Project SEED is planned at Iowa State University.With support from the Engineering Directorate's Division of Emerging Frontiers and Multidisciplinary Activities and the Division of Chemistry, this project will recover the intrinsic value “locked away” within ELPs by using activating chemistries that enable new depolymerization products from ELPs. These enabling technologies will incentivize recovery rather than disposal (which is a particular concern for “hard to recycle” materials such as PVC and PU), reduce dependence on petroleum resources, and prevent plastic wastes from polluting the environment. The project will create transformative new avenues for upcycling common ELPs via activating chemistries and subsequent depolymerization into value-added small molecules, including methods that recombine these molecules into more useful and durable polymer products. A fundamental understanding of how to convert these wastes into valuable small molecules will be gained through an integrated experimental-computational approach that examines the proper conditions for PVC and PU activation and depolymerization. The synthesis of TPE materials via partial depolymerization of PET and PVC and subsequent recombination of these oligomers promises to create much more valuable and useful polymer materials from waste. The research plan emphasizes understanding reaction mechanisms and selectivity, product analysis/identification, separation of the depolymerization products of PVC and PU, and characterization of TPE materials.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.