Buback, M.; Hesse, P.; Lacik, I.
Propagation rate coefficient and fraction of mid-chain radicals for acrylic acid polymerization in aqueous solution
Macromolecular Rapid Communications 2007, 28, 2049-2054.
 

In acrylate polymerizations both SPRs and tertiary MCRs occur. Via pulsed laser polymerization, using a wide range of LPRRs, in conjunction with aqueous-phase size-exclusion chromatography, the polymerization of 1.35 mol · L^-1 acrylic acid in aqueous solution has been investigated at 6 °C. The sigmoidal decrease in the apparent propagation rate coefficient, k_p, towards lower LPRRs is in line with recent predictions. At the highest LPRRs, k_p approaches the rate coefficient of SPR propagation, k_p, whereas the limiting value of k_p at low LPRRs approaches the effective propagation rate coefficient, k_p, which allows for an estimate of the fraction of MCRs under polymerization conditions, x^MCR.