RAFT/MADIX rate coefficients measured via time-resolved EPR spectroscopy after pulse laser initiation

Addition and fragmentation rate coefficients, k(ad) and k(beta), 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 degrees 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) x 10(4) L mol(-1) s(-1) and k(beta) = (2.3 +/- 0.3) x 10(3) s(-1). The associated K(eq) = k(ad)/k(beta) 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. (C) 2010 Elsevier Ltd. All rights reserved.