STUDY ON THE MECHANISM OF THE CATIONIC POLYMERIZATION OF CYCLOHEXENE OXIDE INITIATED BY THE PHOTOSYSTEM OF POLY(METHYL PHENYL SILANE) AND PYRIDINIUM SALTS

The initiation process of photoinduced polymerization of cyclohexene o xide (CHO) in the presence of pyridinium salts and poly(methyl phenyl silane) (PMPS) was investigated by CW-ESR, time-resolved ESR, F-19 NMR , and by the polymerization behavior with three kinds of pyridinium sa lts. The results of CW-ESR measurements suggest that photolysis of PMP S under UV irradiation at wavelength longer than 310 nm mainly through main-chain scission. The facts that the life time of the transient ra dicals of PMPS under irradiation decreased significantly when N-ethoxy -2-methyl pyridinium hexafluorophosphate (EMP(+)PF(6)(-)) was added su ggest that single electron transfer from the silyl radicals to EMP(+) ions took place. The polymerization of CHO could be easily initiated b y irradiation (lambda(inc) = 345 nm) on dichloromethane solutions of C HO containing EMP(+)PF(6)(-) and PMPS. However, no polymerization of C HO took place when ClO4- or I- was the counter ion of EMP(+) ions. Thi s effect of the counter ion on the polymerization of CHO indicates tha t the silylenium ion, obtained by the electron transfer reaction from silyl radical, hardly initiates the polymerization of CHO. When the co unter ion of EMP(+) ion is PF6-, PF5, produced by the reaction of sily lenium ion with PF6-, is considered to be an initiator for the polymer ization of CHO, because Si-F bond, which is obtained by the F- abstrac tion of silylenium ion from PF6-, was found in residual hexane-insolub le polysilanes by F-19 NMR spectroscopy.