1.
Macromol Rapid Commun
; 30(23): 1969-74, 2009 Dec 01.
Artigo
em Inglês
| MEDLINE
| ID: mdl-21638484
RESUMO
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) .