Effects of chain length and size of alkyl group in radical polymerization of dialkyl fumarates as studied by electron paramagnetic resonance spectroscopy

Propagating radicals of diethyl and diisopropyl fumarates are detectable by electron paramagnetic resonance (ESR) spectroscopy in homogeneous systems at room temperature or above. Resolution of the spectra was found to be much improved by raising the temperature to 120°C, and the spectra are shown to correspond to three components according to chain length. Composition of the spectra was dependent on the polymerization conditions. The hyperfine splitting constants were determined by computer simulation of the spectra. The coupling constant for the α‐hydrogen is noted to be as small as 3 to 4 G, and those for the β‐hydrogen are ca. 4, 14 and 30 G.