Electron spin resonance study of trimethylolpropane monoallyl ether in radical polymerization

Trimethylolpropane monoallyl ether (TMP) was studied with an x-band electron spin resonance (ESR) spectrometer by applying a flow method, developed by Dixon and Norman, in which TMP was subjected to hydroxyl radical attack. The observed ESR spectra were assigned to two radicals formed by addition of hydroxyl radical to TMP and one by abstraction of hydrogen from the allylic group of TMP. The ESR spectra from copolymerizing systems of vinyl acetate (VAc) and methyl acrylate (MA) with TMP were also studied. In the system VAc-TMP, the ESR spectrum showed in addition to VAc radicals the presence of the three TMP radicals. In the system MA-TMP, the ESR spectrum was mainly due to TMP radicals in which the allylic radicals were dominant. This result is consistent with the observation that polymerization of MA is strongly retarded by the addition of TMP, which is interpreted as due to the high reactivity of MA radicals to TMP monomer.