Kinetics of Direct Photoinduced Addition of Carbosilane Thiols with Bulky Groups to Polyallylcarbosilane

Abstract

The kinetics of the addition of carbosilane thiols of various structures to a hyperbranched polyallylcarbosilane matrix in n-hexane solution under direct photoinitiation is studied. A kinetic scheme that makes it possible to describe the photoaddition reaction at the quantitative level is proposed. The reaction rate constants are determined, and the dependence of the differential quantum yield of the photochemical reaction on the kinetic parameters and the concentration of allyl groups in the polyallylcarbosilane matrix is obtained. The assignment of the absorption bands to the corresponding components of the reaction system is confirmed by the quantum-chemical calculations of transition energies and oscillator strengths of the chromophore groups of thiols and the resulting thioesters. It is shown that the lowest rate of thiol-ene addition is observed for thiol with the smallest length of a polymethylene spacer between sulfur and silicon atoms.