A facile, simple, and inexpensive ionic liquid, 1-alkyl-3-methylimidazole chloride, as ligand for the iron(iii)-mediated reverse atom transfer radical polymerization of methyl methacrylate

Abstract

Over the past few years, ionic liquids (ILs) have been widely reported as reaction media for reverse atom transfer radical polymerization (ATRP). In particular, almost all the ILs with the structure [Hmim][RCOO] (R represents an alkyl group) have been used as ligands for a reverse ATRP system. However, the facile, simple and low-cost ILs, 1-alkyl-3-methylimidazole chloride ([Rmim][Cl]), have rarely been employed as ligands for reverse ATRP. In this article, a [Rmim][Cl] was successfully employed as a ligand for the reverse ATRP of methyl methacrylate with Fe(III) as catalyst and 2,2′-azobisisobutyronitrile as initiator. The key to success is to adjust the FeCl₃/[Rmim][Cl] molar ratio value to 1 : 1. The results indicated that the polymerization with [Rmim][Cl] as a ligand proceeded in a controlled/“living” fashion, as evidenced by the first-order kinetic plot, low polydispersity index values, and increase in polymer molecular weight with monomer conversion. The effects of various experimental parameters, including different catalysts, reaction temperatures, solvents, and molar ratios of FeCl₃/[Rmim][Cl], on the polymerization were investigated in detail. Furthermore, ¹H NMR and gel permeation chromatography analyses confirmed the halogen-containing chain-end functionality of the resultant polymer.