Elastic properties of polymeric Langmuir-Blodgett films studied using Brillouin light scattering.

Abstract

Brillouin light scattering (BLS) experiments have been performed on polymeric uniaxial Langmuir-Blogett (LB) films, whose preferred axes are in the plane of the film, to investigate their elastic properties. By assigning the spectral signals unambiguously, the whole set of the elastic constants and the indices of refraction were determined. As the monolayer thickness increased from 16.5 to 20.5 A, the elastic constants decreased and the refractive indices were not changed. These decreasing elastic constants were interpreted in terms of a superlattice model of the polymeric LB films. BLS coupled with surface-plasmon-polaritons was studied to not only enhance the Brillouin signal by more than a factor of 15, but also to study the hybridization of the dispersion relations between the guided modes of a CdA LB film and the Rayleigh-Sezawa modes of the supported Ag film coated on a prism. The Kretschmann ATR geometry was used. The angular dependence of the intensity of the surface-plasmon-polariton-enhanced BLS for a prism-metal-dielectic system was also studied.