Entropy-Regulated Selective Synthesis of Cyclic Polymers and Polycatenanes by Lewis Pair Polymerization

While cyclic polymers offer a suite of unique material properties relative to their linear counterparts, their precision synthesis remains challenging and often relies on highly dilute reaction conditions to promote topological selectivity. Here, we unravel the nature of a Lewis pair polymerization (LPP) system that has demonstrated itself to be an exception to this general rule. To understand the unique, apparently concentration-independent, topological selectivity observed within this LPP system, we have paired specifically designed experimental studies with computational calculations to develop a mechanistic framework centered on an entropically driven dynamic equilibrium between intermolecular and intramolecular forms of electrostatic preorganization of polymer termini. This nuanced perspective provides a conceptual platform for the future design of topologically selective polymer synthesis. Notably, the polycatenane formation within this system under high concentrations provides strong support for the proposed mechanism. Overall, this work not only provides fundamental insights into the role of chemical dynamics in the precision synthesis of cyclic polymers but also establishes the convenient route toward topologically complex polymers.