Eight homologous amphiphilic polysilanes bearing an ammonium moiety in the side substituent were synthesized. The spreading behavior at the air-water interface of these polysilanes, molecular film fabrication by the Langmuir-Blodgett (LB) technique, and their UV absorption properties and structural features were investigated. The UV absorption spectrum of the transferred LB films was dependent on the deposition condition, such as the existence of a hydrophobic counteranion in the substrate and the magnitude of mechanical compression by the moving barrier. Such spectral changes should be coupled with conformational changes, i.e., trans/gauche populational changes of the Si backbone modified at the air-water interface. A related conformational modification was achieved when the polysilane monolayer was mixed with stearic acid as the lateral spacer. Polarized UV spectroscopy revealed that the Si backbone is preferentially oriented along the dipping direction possibly due to flow orientation on the water surface. This orientational order depended strongly on the molecular structure of the polysilane and the deposition number. The hydrocarbon side chain, the layer structure, and the morphology of the LB films were evaluated by Fourier transform infrared spectroscopy, transmittance electron microscopy, and X-ray reflectometry. These measurements put forth a view that the LB films are composed of periodical double layers having a homogeneous and amorphous character. Furthermore, a multilayered LB film having the aligned Si backbone promoted homogeneous alignment of a nematic liquid crystal in the dipping direction.