Intramolecular Quaternization as Folding Strategy for the Synthesis of Catalytically Active Imidazolium-Based Single Chain Nanoparticles.

Abstract

A novel synthetic strategy to single chain nanoparticles (SCNP) based on a previously unexplored intramolecular reaction as a means to autonomously fold a parent copolymer precursor is reported. The latter is a statistical styrenic-type copolymer synthesized by RAFT polymerization and is composed of four different comonomer units, including styrene, grafted poly(ethylene oxide) chains, and antagonist benzimidazol- and chlorobenzyl-based units. The two latter functions are reacted together by a quaternization reaction to spark the folding process, creating imidazolium-based cross-link points. Formation of SCNP with a hydrodynamic diameter <10 nm is established by a combination of different characterization techniques. A subsequent metathesis step for exchanging chloride anions by acetate ones of imidazolium moieties enables a use of SCNP for the organocatalyzed benzoin condensation, thanks to the ability of imidazolium acetate to generate SCNP-supported N-heterocyclic carbenes as organocatalysts.