(662b) Polymer Melt Dynamics on Catalyst Surfaces Using Replica Exchange Molecular Dynamics Simulations

Global plastic production has increased exponentially over the last decades and reached over 400 Mt in 2017 (290 Mt of plastic waste every year).¹ Chemical recycling/upcycling has gained significant attention in heterogeneous catalysis to achieve a circular economy. The heterogeneously catalytic reaction of plastics (polymers) occurs at the catalyst-polymer interface. Thus, the structural properties of the polymer on the surface (e.g., which C-C bond is adsorbed) govern the product carbon distribution determining the product. In this context, we developed a methodology using Replica Exchange Molecular Dynamics simulations and the Multi-State Bennett Acceptance Ratio to investigate the structural properties of polymer melts in the adsorbed layer. We applied it to various polyethylene chains and branched polymers. The data indicates that short-chain polymers, e.g., C₂₆, prefer to be fully absorbed, i.e., the energy gained by adsorption overrides the entropic penalty associated with chain propagation along the z direction. Increasing chain length results in a change in the polymer dynamics. Finally, we relate our simulation results with the product distribution we obtain experimentally.

[1] United Nations Environment Programme, Drowning in Plastics –Marine Litter and Plastic Waste Vital Graphics (2021).