EPR Investigations into the Kinetics of Trithiocarbonate-Mediated RAFT-Polymerization of Butyl Acrylate

Electron paramagnetic resonance (EPR) spectroscopy is used for measuring rate coefficients of addition, k(ad), and fragmentation, k, together with the associated equilibrium constants, K-eq, for butyl acrylate polymerizations mediated by S-ethyl propan-2-ylonate-S'-propyl trithiocarbonate (EPPT) and by S-S'-bis(methyl-2-propionate) trithiocarbonate (BMPT). Experiments at -40 degrees C yield k(ad) = (3.4 +/- 0.3) x 10(6) L mol(-1) s(-1), k = (1.4 +/- 0.4) x 10(2) s(-1), and K-eq = (2.6 +/- 0.8) x 10(4) L mol(-1) for EPPT and k(ad) = (4.1 +/- 0.9) x 10(6) L mol(-1) s(-1), k = (4.5 +/- 0.5) x 10(1) s(-1), and K-eq = (8 +/- 4) x 10(4) L mol(-1) for BMPT. The K-eq values are in satisfactory agreement with data from ab initio calculations.