title: EPR Analysis of n-Butyl Acrylate Radical Polymerization.
abstract: Via electron paramagnetic resonance (EPR) spectroscopy, concentrations of secondary propagating radicals (SPRs) and tertiary mid-chain radicals (MCRs) in n-butyl acrylate solution polymerization were measured. The EPR spectrum is dominated by the 4-line spectrum of SPRs at -50 °C and by the 7-line spectrum of MCRs at +70 °C. At intermediate temperatures, a third spectral component is seen, which is assigned to an MCR species with restricted rotational mobility. The MCR components are produced by 1,5-hydrogen shift (backbiting) of SPRs. The measured ratio of MCRs to SPRs allows for estimating the rate coefficient k pt for monomer addition to a mid-chain radical. For 70 °C, k pt is obtained to be 65.5 L · mol(-1)  · s(-1) .
authors.affiliation: Institut für Physikalische Chemie, Georg-August-Universität Göttingen, Tammannstrasse 6, D-37077 Göttingen, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Barth
authors.forename: Michael
authors.initials: M
authors.lastname: Buback
authors.forename: Pascal
authors.initials: P
authors.lastname: Hesse
authors.forename: Tatiana
authors.initials: T
authors.lastname: Sergeeva