Meiser, W.; Buback, M.; Barth, J.; Vana, P.
RAFT/MADIX rate coefficients measured via time-resolved EPR spectroscopy after pulse laser initiation
Polymer 2010, 51, 5977-5982.
 

Addition and fragmentation rate coefficients, k_ad and k_β, have been measured by individually tracing intermediate and propagating radical concentrations via highly time-resolved EPR spectroscopy after applying a laser single pulse. The method is illustrated for butyl acrylate polymerization at −40 °C with EDTCP (ethyl 2-[1-diethoxyphosphoryl-2,2,2-trifluoroethoxythio carbonylsulfanyl] propionate) being the MADIX agent. Analysis of the radical concentration vs. time profiles yields k_ad = (2.5 ± 0.1) × 10⁴ L mol⁻¹ s⁻¹ and k_β = (2.3 ± 0.3) × 10³ s⁻¹. The associated K_eq = k_ad/k_β value is in close agreement with K_eq deduced from an earlier EPR method which rests on measuring the ratio of intermediate and propagating radical concentrations during stationary polymerization.