Photochemical transformations in polysilanes upon irradiation with UV and visible light

The effect of UV and visible light on the properties of poly[methylcyclohexyl-co-methyl(β-trimethylsilyl)ethyl]silane (molar composition of copolymer 3 : 2) and polymethylphenylsilane solutions was studied. It was shown that UV irradiation causes photodegradation of the polysilane chain. A correlation between the molecular mass of the polymers and the wavelength of the absorption maximum in the UV spectrum was established. This correlation makes it possible to determine the length of conjugated chain fragment for a compositionally homogeneous copolymer of a given composition. On the basis of log[η]-logM plots obtained with fractions of polymethylphenylsilane and unfractionated samples, it was found that, upon longterm exposure of solutions of polysilanes to visible light, their macromolecules become branched.