PME DISTINGUISHED COLLOQUIUM SERIES - Thomas H. Epps, III

Advanced Recycling-Understanding Fundamentals to Valorize Biomass and Plastics Waste

Approaches that valorize biomass and plastic waste have continued to emerge in recent years. One common strategy is deconstruction/depolymerization, whereby polymers are degraded into smaller molecules by various reaction pathways. The dynamics of these complex systems of molecules, with evolving molecular weights and molecular weight distributions that span the range from monomer up to commodity polymer, are a strong function of process technology. Hence, efficient development of deconstruction technologies and potential application-oriented use cases will benefit from simple and descriptive models that link material characteristics and process parameters to physical properties and product distributions. We have applied these models and learnings to both biobased and petroleum-based macromolecules. As examples, we have recently achieved the chemical recycling and upcycling of two higher-glass-transition temperature (> 100 °C), lignin-derivable polymethacrylates, poly(syringyl methacrylate) (PSM) and poly(guaiacyl methacrylate) (PGM). Neat PSM and PGM were thermally depolymerized to quantitative conversions, producing their constituent monomers at high yields and purity in both N2 and air. We were able to scale these analytical insights to the bulk depolymerization of free-radically polymerized PGM and PSM under dynamic vacuum without solvent or catalyst to high polymer conversions (89-90 wt.%) and monomer yields (86-90 mol%) without byproduct formation. The resultant monomers were then upcycled without further purification to narrow-dispersity polymers and phase-separated block polymers via controlled polymerization. Additionally, we have made similar progress in heteroatom-containing, petroleum-based feedstocks, demonstrating the ability to chemically depolymerize both thermoplastics and thermosets back to monomers that can be repolymerized to generate upgraded polymeric materials. Overall, these studies offer new pathways to ‘closing the loop’ on the life cycle for higher-performance polymer systems.

Zoom Meeting ID: 922 9641 0141 Passcode: 580746