Surface analysis of polyethylene and hexatriacontane by high resolution electron energy loss spectroscopy

Abstract

Surfaces of polyethylene and n-hexatriacontane were for the first time studied by high resolution electron energy loss spectroscopy (HREELS). The vibrational band energies and intensities were recorded and compared to transmission infrared data. The attribution of most of the bands to methyl, methylene, and C–C vibrations is straightforward; but some of the bands remain unassigned. The intensities of the methyl associated electron energy losses are greatly enhanced. This confirms the extreme surface sensitivity of the spectroscopy and is consistent with a C–C skeleton preferentially oriented perpendicular to the surface. Measured cross section data vs electron impact energy (E0) show that while a dipolar-type interaction mechanism is dominating some regions of the cross-section curve, other resonance scattering may contribute significantly for low and high E0. This cross-section curve shows also that the polymer surfaces are to be considered as a ‘‘condensed gas,’’ with weak intermolecular interaction, instead of a real solid state material with collective (phonon) vibrational excitations. No evidence of radiation damage could be found in the vibrational spectra.