Investigation of eATRP for a Carboxylic-Acid-Functionalized Ionic Liquid Monomer

Electrochemically mediated atom transfer radical polymerization (eATRP) is a promising technique for precise control over polymer molecular weights (MWs), molecular weight distribution (Đ), and complex architectures under low concentrations of copper-based ATRP catalysts. Herein, eATRP of ionic liquid monomer (ILM), 1-vinyl-3-propionate imidazolium tetrafluoroborate (VPI⁺BF₄⁻), containing carboxylic acid groups is inquired in aqueous media. In the polymerization process of water-soluble VPI⁺BF₄⁻, the protonation and dissociation of catalysts have great influence on the polymerization reaction. Various polymerization parameters, including applied potential (E_app), pH, degree of polymerization (DP) (from 100 to 300), and the catalyst concentration (from 5 × 10⁻⁴ to 1.5 × 10⁻³ m) are examined. Under certain polymerization conditions, poly(ionic liquids) (PILs) with a well-controlled MWs and narrow Đ are obtained. The controlled/living property of the polymerization process is reflected by the linear first-order kinetics, linear increase of MWs with monomer conversion, and the probability of complete reactivation of the polymerization by repetitively altering the E_app values. This work provides a new perspective for the precise synthesis of PIL-based block copolymers with adjustable properties; meanwhile, the eATRP of monomer containing carboxylic acid groups is expected to develop functional materials with pH responsiveness and biocompatibility.