Vibrational and electronic excitations in poly(methylphenylsilane) and poly(diphenylsiloxane) films: Surface aspects

High-resolution electron energy loss spectroscopy (HREELS) is applied to st udy film surfaces of two silicon-leased polymers hating. methyl and/or phen yl rings as pendant groups: poly(diphenylsiloxane) and poly(methylphenylsil ane). These spectra are compared with those obtained by infrared absorption , Raman scattering, and UV/vis absorption spectroscopy for the polymer bulk . Both vibrational and electronic spectra of these two polymers exhibit com mon features corresponding to the phenyl pendant group excitations. Positio ns of peaks appearing in HREELS vibrational spectra correspond well to infr ared- and Raman-active modes of the polymer bulk. Electronic losses also co rrespond to the electronic excited states of phenyl groups cited in the lit erature. Differences related to secondary emission and accumulation of rela xed electrons are assigned to the electronic structure of the film. The abs ence of a loss corresponding to the excitation of polysilane chain is relat ed to a trapping mechanism.