New precursors to SiCO ceramics derived from linear poly(vinylsiloxanes) of regular chain composition

摘要

Two linear polysiloxanes with vinyl groups regularly distributed in their chains (D_2V polymer with a vinyl group at every third and V_3 polymer with a vinyl group at each Si atom) were cross-linked with different hydrogensiloxanes (linear difunctional ~HMM~H, linear branched tetrafunctional Q(M~H)_4, cyclic tetrafunctional D_4~H) and studied as new precursors to SiCO ceramics. It was found that thermal properties of the cross-linked D_2V and V_3 polymers are governed mainly by functionality of the initial macromolecule as well as functionality and molecular structure of hydrogensiloxane. Transformation of the systems into ceramics was examined by recording FTIR spectra of the samples obtained after heat treatment of the cross-linked polymers under Ar at several temperatures. Analysis of the products formed at 1000 ℃, allowed establishing that they are a mixture of silicon oxycarbides and a free carbon phase. Lack of pores is a characteristic feature of these materials.