Decrystallization Free Energy in Polyesters: Insights from Molecular Dynamics Simulations

Continued breakthroughs in catalytic deconstruction strategies for commodity semicrystalline plastics are essential to addressing the global crisis of plastics pollution. We have developed a molecular dynamic-based protocol to estimate the potential of mean force to decrystallize a single chain from the polymer crystal surface in water. The decrystallization work is an essential element of many depolymerization strategies for semi-crystalline polymers including for hydrolase enzymes prior to chain cleavage. Five synthetic polyesters of commercial and scientific interest (PET, PBT, PEF, PEN, and PTT) were examined including PET, the world's most consumed polyester. Our calculations indicate free energy barriers in the range from ~15 kcal/mol (PEN) to ~8 kcal/mol (PEF) per monomer. Our results give insight into the molecular interactions that form the structural basis of semi-crystalline synthetic polyesters, providing guidance to experimentalists pursuing more efficient plastic recycling and upcycling strategies, which could include catalyst development, fine-tuning conditions during the recycling process including pretreatment, enzyme and chemical selections, and design of new materials.