Both structural and kinetic investigations of radicals in polymerizations have been conducted by various ESR technique using ATRP. Time-resolved electron spin resonance (TR ESR) spectra allowed direct observation of transient radicals (chain initiating radical) obtained by the addition reaction of a diphenylphosphinoyl radical to vinyl monomers. Since TR ESR spectroscopy is based on chemically induced dynamic electron spin polarization (CIDEP) phenomenon, highly polarized radical can be detected as ESR signal and signal intensity is not correlated with the radical concentrations. Even if transient radical concentrations are lower than the lower limit of sensitivity of conventional steady-state ESR, highly polarized radicals can be detected by TR ESR spectroscopy. Figure 1 shows TR ESR spectrum of tert-butyl methacrylate (tBMA) initiated by 2,4,6-trimethylbenzoyl diphenylphosphine oxide (TMDPO).Mechanism of radical migration during polymerizations of acrylates has been clarified using oligo- and polymeric model radicals generated from precursors prepared by ATRP. There are many factors that affect the rate of the migration. Dependencies on chain lengths, side group structures, monomer unit sequences, and stereo-chemical differences have been examined.

ESR investigations of radicals in polymerizations by various magnetic resonance technique with the aid of ATRP

248th National Meeting (2014)

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