Radical polymerization kinetics of water-soluble monomers

Radical polymerization of monomers with functional groups such as carboxylic acid and amide moieties yields materials of significant technical importance. The reactions are mostly carried out in aqueous phase, which provides the additional advantage of using a cheap and benign solvent. In addition to varying monomer concentration, temperature and pressure, the kinetics and thus the polymer properties may be tuned by varying the degree of monomer ionization, by changing pH and ionic strength of the aqueous solution, and by addition of an organic cosolvent. These systems exhibit strong interactions via hydrogen bonds resulting in large effects on rate coefficients, even for propagation, which for long have been considered as almost insensitive towards solvent environment. The determination of rate coefficients in aqueous solution largely assists the understanding of the impact of intermolecular interactions on polymerization rate. Despite the enormous importance of polymers produced by radical polymerization in aqueous solution, the associated mechanism and the availability of accurate rate coefficients have been very limited. This situation has improved by applying pulsed-laser techniques, which enable the precise measurement of individual rate coefficients in aqueous solution as required for the simulation of radical polymerization processes.