Linda Shimizu’s group, in collaboration with Sophya Garaschuk’s group at the University of South Carolina, recently investigated the supramolecular polymerization of a novel m-terphenyl bis-urea macrocycle. Led by the graduate student G.I.P. Wijesekera, this research was recognized as a Very Important Paper in Chemistry – A European Journal, highlighting its significance in the field of supramolecular chemistry. Unlike conventional supramolecular polymers that assemble in thermodynamically controlled pathways, this macrocycle exhibits cooperative polymerization with kinetic trapping, allowing unprecedented control over polymer growth and dissociation.
Using a combination of spectroscopic and computational techniques, the team identified thermal hysteresis effects, where the assembly and disassembly processes follow distinct pathways due to energy barriers that lock monomers in metastable states. This behavior suggests that polymerization is governed not solely by thermodynamic stability but also by kinetic constraints that modulate molecular interactions over time. Electronic structure calculations further revealed a critical conformational shift in the monomer, which dictates polymerization rates and determines the formation of either kinetically trapped or thermodynamically stable structures. These findings highlight the complex interplay between molecular conformation and supramolecular assembly, providing a strategy to manipulate polymerization kinetics through molecular design.