Abstract
Radical polymerizations of methyl α-ethylacrylate (MEA) and cyclohexyl α-ethylacrylate (CHEA) in bulk were kinetically investigated on the basis of the absolute rate constants of elementary reactions evaluated by ESR spectroscopy. ESR spectra of the propagating radicals from MEA and CHEA were observed as five-line spectra by accumulation of a few scans during the slow polymerization of MEA and CHEA to low molecular weight (M̅n=1000–4000). The rate constants of propagation and termination (kp and kt) were determined based on quantification of propagating radicals from the α-ethylacrylates: kp=8.6 and kt 2.1×107 L mol−1 s for MEA, and kp=1.6 and kt=1.8×106 L mol−1 s for CHEA. The steric hindrance of the ethyl group was found to bring about slower propagation and slightly slower termination rates of MEA in comparison with methyl methacrylate (MMA). The detailed structural analysis of the end group in the polymer indicates that replacement of the α-methyl group of MMA with the ethyl group of MEA results in termination involving mainly combination (76%). The steric hindrance seems to affect the termination mode.
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Kobatake, S., Yamada, B. Sterically Hindered Elementary Reactions in Radical Polymerization of α-Ethylacrylic Esters as Studied by ESR Spectroscopy. Polym J 28, 535–542 (1996). https://doi.org/10.1295/polymj.28.535
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DOI: https://doi.org/10.1295/polymj.28.535
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