Kilohertz Pulsed-Laser-Polymerization: Simultaneous Determination of Backbiting, Secondary, and Tertiary Radical Propagation Rate Coefficients for tert-Butyl Acrylate

For the first time, a 1000 Hz pulse laser has been applied to determine detailed kinetic rate coefficients from pulsed laser polymerization-size exclusion chromatography experiments. For the monomer tert-butyl acrylate, apparent propagation rate coefficients k(p)(app) have been determined in the temperature range of 0-80 degrees C. k(p)(app) in the range of few hundreds to close to 50 000 L.mol(-1).s(-1) are determined for low and high pulse frequencies, respectively. The apparent propagation coefficients show a distinct pulse-frequency dependency, which follows an S-shape curve. From these curves, rate coefficients for secondary radial propagation (k(p)(SPR)), backbiting (k(bb)), midchain radical propagation (k(p)(tert)), and the (residual) effective propagation rate (k(p)(app)) can be deduced via a herein proposed simple Predici fitting procedure. For k(p)(SPR), the activation energy is determined to be (17.9 +/- 0.6) kJ.mol(-1) in excellent agreement with literature data. For k(bb,) an activation energy of (25.9 +/- 2.2) kJ.mol(-1) is deduced.