A Multidisciplinary Investigation of Polymer-Catalyst Interfaces in Chemical Recycling

Plastics are ubiquitous polymeric (long, chain-like structured) materials. Every year, large quantities of waste are generated from single-use plastic products, threatening the health and life quality of residents near disposal sites and representing an inefficient way of utilizing petroleum resources. Chemical recycling processes convert plastic waste back into its building blocks, or into value-added products, achieving a “circular” plastic sector. The chemical bonds in plastic polymers are identical with those in small-molecule petroleum compounds, but the two behave drastically differently during recycling reactions. This project will characterize such discrepancies by probing the interactions between plastic polymers and catalyst surfaces. The resulting insights will reveal the distinct behaviors of polymer chains from small compounds at such catalytic interfaces, and in turn, their unique chemical reactivities. This fundamental knowledge will enable the rational design of catalytic processes to improve the efficiency of chemical plastic recycling, hence contributing to the circular utilization of petroleum and helping address the growing plastic waste challenge. The project will include educational and outreach initiatives promoting STEM opportunities for K-12 students, and training opportunities for both undergraduate and PhD students in a highly collaborative and interdisciplinary team-research setting. This project will improve the understanding of the polymer-catalyst interface by combining expertise from three research groups in precise polymer synthesis, spectroscopic characterization and catalytic kinetics, and computational modeling. Plastic polymers of well-defined microstructures and narrow dispersity will be synthesized and purified to delineate effects from different structure parameters. The team will conduct neutron scattering and nuclear magnetic resonance studies to address the conformation and dynamics of these polymer chains around model catalytic interfaces. Kinetics of catalytic recycling will be carefully evaluated in reactors, and correlated with spectroscopy-derived chain behaviors. The experimental evidence of structure-dependent macromolecular behaviors, kinetics, and reaction mechanisms will be further elucidated through multiscale modeling, including first-principles calculations and machine learning-assisted molecular dynamics simulations. This multidisciplinary approach will enable deciphering the complex polymer-catalyst reactive interface holistically, and thus transform the level of accuracy in understanding chemical plastic recycling processes. 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.