Large-Scale Synthesis of Polymer Rings by Electrostatic-Mediated Closure of Single-Chain Nanoparticles

Polymer rings are unique over their linear counterparts in fundamental and engineering aspects. Although ring closure of polymers is a proven general method toward rings, the large-scale synthesis in concentrated solutions remains challenging due to the concurrent intermolecular reactions. Herein, we propose the electrostatic-mediated ring closure of polymers in the dynamic single-chain nanoparticle (SCNP) globular state, enabling large-scale synthesis of highly pure polymer rings at an unprecedentedly high concentration of 150 mg/mL. The dynamic SCNPs are also achieved by the electrostatic-mediated intramolecular cross-linking of polymers in concentrated solutions. Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA)-based telechelic polymers are selected to demonstrate the concept. The charged dynamic SCNPs are constructed by simple amine-acid-specific interactions, and thiol–ene and Diels–Alder click reactions are employed for the ring closure to demonstrate the generality. The microstructure and composition of the rings can be tuned from the corresponding polymers with varied segmental sequences and compositions. The topology and function can be further tuned by the favorable growth of functional materials at the desired sites of the polymer rings.