IR spectra and structure of polyethylene coatings on silicon and germanium single-crystal substrates

The IR spectra and structure of coatings consisting of gas-phase polyethylene powder on single-crystal substrates of silicon and germanium, modified with bis-(4-amino-3-chlorophenyl) methane, have been analyzed. The spectra were recorded by means of thermostatically controlled optical blocks using both transmission or reflection at 20-160°C. The orientation function of the polymer in the coating was calculated by the Kramers-Kronig method with s- and p-polarization of the incident light. The transition from the free PE film to the coating is accompanied, in the region of the torsion-fan vibrations of the CH2 groups, by a redistribution of the intensity of the bands at 1085, 1155 and 1303 cm-1. The relative increase in the band at 1155 cm-1 is caused by the orienting effect of the substrate on the polymer macromolecules. The introduction of a modifier leads to an increase in the structural anisotropy of the coating. It is shown that there is a maximum in the dependence of the intensity of the band at 1303 cm-1 on the modifier concentration. The contribution of planar structures decreases as the modifier is introduced. The reduction of the intensity of the band at 1155 cm-1 as the modifier concentration is varied is caused by a reduction in the proportion of the more ordered amorphous phase (the mesophase) in the coating. The boundary layer of the coating at a distance of 0.5-1.0 μm from the substrate surface consists predominantly of macromolecules forming the mesophase; around 80°C, the macromolecules in the boundary layer become disoriented and the mesophase transforms into the ordinary amorphous condition.