Photodegradation of Alkyl-and Aryl-Substituted Polysilanes Studied by Flash Photolysis

The photodegradation of poly(cyclohexylmethylsilane) and poly(phenylmethylsilane) was investigated by flash photolysis and quenching experiments. The time-resolved absorption spectra of poly(cyclohexylmethylsilane) showed a sharp transient absorption peak at 370 nm with an absorption shoulder near 430 nm. These transient absorption bands were reasonably assigned to silyl radical by quenching experiments using methylene chloride as a radical quencher. The wavelength dependence of the intermediate during photodegradation was observed for poly(phenylmethylsilane). The transient absorption spectrum obtained by the excitation at longer wavelength (σ, σ* band region) showed a broad transient absorption near 400 nm. This was assigned to silyl radical by quenching experiments using methylene chloride as a quencher. When polyiphenylmethyleilane) was excited at shorter wavelength (π, π* band region), an additional transient absorption appeared near 480 nm, which was assigned to be silylene using triethylsilane as a silylene trapping agent.