title: Addition Rate Constants of Phosphorus- and Carbon-Centered Radicals to Double Bond of Monomers as Studied by a Pulsed Electron Paramagnetic Resonance Method.
abstract: Addition reaction of a radical to the double bond of a monomer, which is important at early stage of photopolymerization, has been studied by time-resolved (TR-) and pulsed electron paramagnetic resonance (EPR) spectroscopic methods. Reactions of one phosphorus-centered and three carbon-centered radicals attacking to several monomers have been employed. Intermediate radicals were identified by analyzing the recorded TR-EPR spectra, and the reaction rate constants were determined by the electron spin-echo detection method proposed by Weber and Turro [J. Phys. Chem. A, 2003, 107 (18), 3326 - 3334]. The quantum chemical calculation shows that the rate constants for the addition reactions are well-explained by introducing two factors of "enthalpy effect" and "polar effect" to control the activation barrier height. It was observed that the rate constants of the phosphorus-centered radical were larger than those of carbon-centered radicals for some monomers. The difference in the rate constants was argued on the basis of frequency factor and activation barrier both of which are influenced by an atom of radical center.
authors.affiliation: †Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 H89 Ohokayama, Meguro-ku, Tokyo 152-8551, Japan.
authors.forename: Hirona
authors.initials: H
authors.lastname: Takahashi
authors.affiliation: †Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 H89 Ohokayama, Meguro-ku, Tokyo 152-8551, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Marushima
authors.affiliation: ‡National Institute of Technology, Gunma College, 580 Toriba-machi, Maebashi, Gunma 371-8530, Japan.
authors.forename: Kazuhide
authors.initials: K
authors.lastname: Tsuji
authors.affiliation: †Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 H89 Ohokayama, Meguro-ku, Tokyo 152-8551, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Shibuya
authors.affiliation: †Department of Chemistry, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 H89 Ohokayama, Meguro-ku, Tokyo 152-8551, Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Kawai