PHOTOREACTION OF ALKOXYPOLYSILANES

The photoreaction of network ethoxypolysilanes ((MeSi)(n)[Me(EtO)Si](m )) using low pressure mercury lamps was investigated in the presence a nd in the absence of oxygen, and was compared with that of poly(hexyls ilyne) and poly(dihexylsilylene). The photoreaction of the ethoxypolys ilanes in the presence of oxygen led to their photooxidation, and resu lted in a decreased molecular weight and the disappearance of ultravio let absorption over 300 nm. The molecular weight of the ethoxypolysila nes was more slowly reduced than that of poly(hexylsilyne). On the oth er hand, photolysis of the ethoxypolysilanes under an inert atmosphere caused an increase in molecular weight, though similar photolysis of the alkylpolysilanes showed a molecular weight decrease. These results could be explained by the influence of the ethoxysilyl groups in the polysilanes. The decomposition of polymer chains would be depressed by the reaction of the alkoxysilyl groups with silanols produced from ph otooxidation and the insertion reaction of silylenes into Si-OEt bonds . (C) 1997 Elsevier Science Ltd.