Propagation rate coefficients, kp, of methyl methacrylate (MMA) and glycidyl methacrylate (GMA) homopolymerizations were measured at ambient pressure in four ionic liquids (ILs): 1‐ethyl‐3‐methylimidazolium ([emim]) ethyl sulfate and [emim] hexyl sulfate as well as butyl‐3‐methylimidazolium ([bmim]) hexafluorophosphate and [bmim] tetrafluoroborate via the pulsed‐laser polymerization size‐exclusion chromatography technique. In passing from bulk polymerization at 40 °C polymerization in IL solution containing 20 vol % monomer, kp is enhanced by up to a factor of 4 with MMA and by a factor of 2 with GMA. This enhancement of kp primarily results from a lowering of activation energy upon partial replacement of monomer by ionic liquid species. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1460–1469, 2008

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For the free radical polymerization of polar monomers which are soluble in ionic liquids (ILs) an extraordinary strong solvent effect can be observed. The solvent influence of the ILs leads to a strong enhancement of the polymerization rate and extremely high, mostly broadly distributed molecular weights. The experimentally determined very high propagation rate coefficient kp and the reduction of the activation energy of propagation EA can be explained by H‐bonds between both the monomer molecules and the growing radical chains and the cations and anions of the ILs. The high viscosity of the ILs themselves as well as the increase of the viscosity during the polymerization process are responsible for the high molecular weights and the mostly high polydispersities. The systematic variation of the rate constants of propagation kp and termination kt using microwave reactor, IL/conventional organic solvent mixtures and increased reaction temperatures is studied.

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