On the Origin of Ionic Liquid-Induced Variations in Hydroxypropyl Methacrylate Propagation Rate Coefficients

Pulsed laser polymerizations were used to study the propagation kinetics of hydroxypropyl methacrylate (HPMA) in ionic liquids (ILs) and common organic solvents. The functional monomer was chosen to investigate the complex interplay of all interactions between monomer molecules and between monomer and solvent molecules and to obtain a deeper understanding of the impact of these interactions. The solvent effect on the HPMA propagation rate coefficient (k(p)) was examined using a linear solvation energy relationship (LSER) based on Kamlet-Taft solvatochromic parameters pi*, alpha, and beta. The results suggest that dipolarity/polarizability, associated with pi*, and hydrogen bond-donating ability of the solvents, accounted for by alpha, majorly contribute to variations in k(p). Hydrogen bond-accepting (electron pair donating) ability of the solvents (beta parameter) is of much lesser importance. In addition, LSER enables the prediction of HPMA k(p) based on solvatochromic parameters of the solvents. The results suggest that interactions between the hydroxyl group of the monomer and the anion are dominant compared with classical hydrogen bonding between carbonyl and hydroxyl groups of the monomer units. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3188-3199, 2010