Valence electronic structures of organopolysilanes having symmetric alkyl side-chains studied by x-ray photoelectron spectroscopy

The valence electronic structures of organopolysilanes having symmetrical alkyl side-chains, i.e., poly(di-n-alkyl silanes) , have been systematically studied by x-ray photoelectron spectroscopy (XPS) for the first time. The specimens used in this work are poly(di-methyl silane) , poly(di-ethyl silane) , poly(di-pentyl silane) , poly(di-hexyl silane) and poly(di-decyl silane) . By comparing the XPS spectra of the poly(di-n-alkyl silanes) with those of normal alkanes, it is found that the spectral features are strongly affected by two factors, i.e., the carbon 2s and 2p electrons in the side-chains and the silicon 3s and 3p electrons in the backbone. The shape of the spectrum from 0 to 5 eV, which is strongly affected by the structure of the valence band edge, shows no significant change with a change in the number of carbon atoms in the alkyl substituents. On the other hand, the splitting of the carbon 2s orbitals in the side-chains strongly affects the shape of the spectrum in the region from 12 to 20 eV. The results are also discussed on the basis of the theoretical calculations as well as the ultraviolet photoelectron spectrum reported previously.