Acceleration of the imine base/isocyanate (IBI)-mediated polymerization of MMA caused by ionic liquid traces

Abstract

The brutto rate of the imine base/isocyanate (IBI)-mediated radical polymerization of methyl methacrylate (MMA) can be significantly increased by use of ionic liquid (IL) traces. At least, catalytic amounts of IL influence both the value of the brutto polymerization rate νBr,0 and the necessary reaction temperature of the used IBI mixture. Combinations of 2-phenyl-2-oxazoline (POX) or 1-methyl pyrazole (1MP) with isocyanates are IBI systems that usually do not initiate MMA at room temperature. By adding traces of 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([Emim]FAP), polymethyl methacrylate (PMMA) with high average molecular weight can be obtained whereas the initiator mixture (imine base/isocyanate) concentration can be decreased by a factor of 10. The polymerization kinetics of several IBI combinations in the presence of ILs has been determined and a comparison to non-IL containing initiator mixtures is given. Additionally, the temperature dependence of the IL-containing polymerizations was measured. The interaction of the IL with MMA and the individual IBI initiator components is studied by means of attenuated total reflection Fourier transformation middle infrared spectroscopy (ATR FT MIR). Furthermore, the IBI brutto polymerization rate constants kBr,0 were brought into relation to the IL hydrogen bond donating ability α. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013