INS and IR Studies of Intermolecular Interaction at the Silicone-Fumed Silica Interface I. Silicones

Vibrations of a set of linear silicone oligomers have been studied experimentally and computationally. Experiments have been performed by using IR transmission technique and inelastic neutron scattering. Both series consist of similar spectra exhibiting a homologous behavior that is provided by the vibrational modes of monomer units mainly. The spectra interpretation has been performed on the basis of extended calculations. The basic force matrix was determined in the course of the QCh semiempirical calculations by using PM3 technique. Harmonic vibrational modes obtained have laid the foundation for the calculation of one-phonon IRT and INS spectra related to the direct spectral problem solution. A quite perfect fitting of experimental and calculated spectra was achieved by a successive solution of a set of inverse spectral problems. The obtained results form grounds for the vibrational mode assignment that, in its turn, provides the basis for the dynamical description of changes of the studied species subjected to adsorption on the fumed silica surface.