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Propagation and chain‐length averaged termination rate coefficients, kp and <kt>, for radical polymerizations of methacrylates carrying poly(ethylene glycol) (PEG) units are reported. kp derived from pulsed laser initiated polymerizations in bulk, in organic solvents, and in ionic liquids follows the methacrylate‐type family behavior. Contrary, diffusion controlled kt values obtained from chemically initiated polymerizations with in‐line FT‐NIR monitoring of monomer conversion are strongly affected by the PEG units in the ester group. Compared to alkyl methacrylates <kt> is unexpectedly high. Moreover, <kt> of poly(ethylene glycol) ethyl ether methacrylate shows a significant reduction in kt already at 15% conversion, whereas dodecyl methacrylate <kt> is constant up to at least 70% conversion.magnified image

Pulsed laser initiated polymerizations of methyl methacrylate (MMA) in the presence of ionic liquids (ILs) resulted in a strong enhancement of the propagation rate coefficient, k p, compared to the bulk system. To correlate the IL influence on MMA k p with IL solvent properties, the Kamlet−Taft parameters α, β, and π* of the ILs were derived. A correlation in the form of ln(k p/k p,bulk) = ln(k p/k p,bulk)0 + sπ*+ aα + bβ was obtained from a linear solvation energy relationship (LSER) analysis of a data set consisting of polymerizations in 11 ILs, as well as in DMSO, in THF, and in bulk. The coefficients are s = 1.72, a = 0.63, b = 0.37, and ln(k p/k p,bulk)0 = −1.27. The data indicate that dipolarity, polarizability, and electron pair accepting ability of the IL, associated with the π* parameter, contribute to a large extent to the variation in k p, whereas electron pair donating and hydrogen bond accepting ability, accounted for by β, are of lesser importance. The hydrogen bond donating ability, related to α, of the IL has no significant influence on k p.

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 (kp) was examined using a linear solvation energy relationship (LSER) based on Kamlet‐Taft solvatochromic parameters π*, α, and β. The results suggest that dipolarity/polarizability, associated with π*, and hydrogen bond–donating ability of the solvents, accounted for by α, majorly contribute to variations in kp. Hydrogen bond–accepting (electron pair donating) ability of the solvents (β parameter) is of much lesser importance. In addition, LSER enables the prediction of HPMA kp 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. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3188–3199, 2010

Propagation rate coefficients, k p , of methyl methacrylate, MMA, homopolymerizations in ionic liquids (ILs) with widely varying structures and physical properties were determined applying the socalled PLP-SEC technique, which combines pulse-laser initiation of the polymerization (PLP) with molecular weight analysis via size-exclusion chromatography (SEC). For all ILs a strong enhancement of k p and a decrease in the activation energy of k p compared to the bulk system were observed. Depending on the IL structure, the increase in k p is between a factor of 2 and 4. Both the cation and the anion are responsible for the enhancement of k p . The smaller the ions of the ILs, the stronger the enhancement of k p . Investigations into the solvent properties of ILs using a solvatochromic dye and infrared spectroscopy suggest that electron pair acceptor-electron pair donator interactions and nonspecific (Coulomb) interactions contribute strongly to the solvent influence, whereas contributions from H bonding are negligible. The knowledge of normalized polarity values of the ILs allows for a rough estimate of the IL-induced variation of k p .