B3LYP investigation of HPO2, trans-HOPO, cis-HOPO and their radical anions

A variety of small poly(dimethyl siloxanes) were irradiated with gamma-rays followed by the determination of the production of methane and molecular hydrogen and characterization of spectroscopic changes in the medium. The yields of methane was found to be about twice that of molecular hydrogen indicating that breakage of the C-Si bond occurs at a frequency comparable to the breakage of the C-H bond. Both yields slowly decrease with increasing molecular weight of the medium. The presence of oxygen decreases the yield of both gases suggesting radical precursors to methane and molecular hydrogen, presumably the methyl radical and H atom, respectively. Temperature gravimetric analysis and UV visible spectroscopy both suggest the formation of higher molecular weight compounds with radiolysis, which agrees with bond loss and formation observed in infrared spectroscopy