V. Polymer Reaction Engineering Free Radical Polymerization in Ionic Liquids - Solvent Influence of New Dimension

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 k p and the reduction of the activation energy of propagation E A 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 k p and termination k t using microwave reactor, IL/conventional organic solvent mixtures and increased reaction temperatures is studied.