Exploring anionic homopolymerization and copolymerization of vinyl monomers in deep eutectic solvent

Abstract

Deep eutectic solvent (DES) represents a kind of eutectic mixture made of two or more substances in a certain ratio with a melting point lower than that of either individual component. As a typical green solvent, DES has been used in polymerization reactions such as condensation polymerization, free radical polymerization, electrochemical polymerization, ring-opening polymerization and oxidative polymerization, but little research has been reported in anionic polymerization. In this work, we explored the anionic homopolymerization, random and block copolymerizations of several vinyl monomers in DES, including styrene (St) and its derivatives (ClSt, MeOSt), isoprene (Ip), and 2-vinylpyridine (2VP). The microstructures and molecular weights of (co)polymers were characterized by nuclear magnetic resonance (1H NMR, 13C NMR), Fourier transform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), while the thermal properties of the copolymers were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results showed that the polymerization products with certain molecular weights, favorable yield and molecular weight distribution could be prepared in DES. In addition, the experimental results indicated that DES can be recycled for polymerization and has little effect on the final product. The anionic polymerization with DES as the reaction medium exhibits mild reaction conditions, which reduces the operational difficulty of traditional anionic polymerization and broadens the application scope of active organolithium reagents.