Electro-induced Cationic Polymerization of Vinyl Ethers by Using Ionic Liquid 1-Butyl-3-methylimidazolium Tetrafluoroborate as Initiator

Ionic liquids are used widely as solvents or electrolytes for electrochemical synthesis and applications due to their wide electrochemical windows, good electrical conductivity, and their excellent solubility to both organic and inorganic compounds. Until now, no papers have reported the use of ionic liquids as initiators in polymerization. In most cases, the kinetics of electro-induced polymerization are studied by gas chromatography (GC), NMR, or the gravimetric method, which are complicated and time consuming. In this paper, the kinetics of electro-induced polymerization of vinyl ethers using ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) as initiator are investigated by real-time Fourier transform near-IR (FT-NIR) spectroscopy. The results show that the ionic liquid BMIMBF4 is an efficient initiator for electro-induced polymerization of vinyl ethers. The final double-bond conversion and polymerization rate can be adjusted by the electric-field intensity and the concentration of the ionic liquid BMIMBF4. Moreover, the post-curing, as well as the obvious inhibition effects of KOH, indicate that the electro-induced polymerization goes through a cationic process. The possible mechanism is also postulated.