✍ Scribed by H.-J. Timpe; A.G. Rajendran
No coin nor oath required. For personal study only.
Abstraet--Epoxides can be polymerized by cations produced by electron-transfer from photochemically generated nucleophilic radicals to onium salts. Effects of various parameters such as absorbed light intensity (la~), onium salt concentration ([On + ]), and type of radical source on the rate of polymerization have been measured and appropriate kinetic expressions explaining these dependencies have been derived. For these studies 2,3-epoxypropyl phenyl ether (phenyl glycidyl ether) was used as monofunctional epoxide. The radical sources were 2,3-dimethoxy 2-phenyl acetophenone (benzil dimethyl ketal) (BDMK), benzoin isopropyl ether (BIPE) and ct-phenyl benzoin (~t-PhB). Diphenyliodonium hexafluorophosphate was the electron acceptor. The quantum yields (q~p) of the polymerization, calculated from the polymerization rate Rp, follow the order BDMK>>BIPE > ~t-PhB. Both iodonium salt concentration and light intensity are related reciprocally to monomer conversion. The kp/k t values calculated from the kinetic expressions lie in the range 22-54 lmol -~.
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