Free-Radical Propagation Rate Coefficients of Dodecyl Methacrylate Deduced from Electron Spin Resonance Experiments

Propagation rate coefficients ( k p ) for the free-radical polymerization of dodecyl methacrylate (DMA) in solution in toluene have been measured via electron spin resonance (ESR) spectroscopy in the temperature range 0 to 50 °C. The polymerization is photochemically induced at different initiator concentrations of di- tert -butyl peroxide (DTBP). Free-radical concentration under steady-state conditions is deduced from double integration of the well-resolved ESR spectra, consisting of 13 lines in the initial period of the polymerization reaction and 9 lines at enhanced degrees of monomer conversion. The k p values from ESR analysis are in excellent agreement with the corresponding data from pulsed laser polymerization (PLP)/size-exclusion chromatography (SEC), the IUPAC-recommended procedure for reliable k p measurement. The activation energy associated with the ESR k p data, E A = 21.7 ± 2.0 kJ mol -1, is in full agreement with E A ( k p ) results from recent PLP−SEC studies.