Liquid-crystal-based films of different thicknesses, fabricated by the Langmuir technology, have been studied. Previously, we revealed a structural phase transition in these films at a temperature of ∼75°C. To clarify the nature of this transition, the temperature dependences of the capacitance and conductance of these films have been investigated. The results obtained indicate that the samples contain a ferroelectric phase, beginning with one monolayer. The film structure imperfection has been revealed using atomic force microscopy, which explains the size of the temperature range in which the phase transition is observed.

Liquid-crystal films prepared by different procedures and having different thicknesses were studied. A structural phase transition was found in these films at ∼75°C. The nature of this transition was examined by investigating the temperature dependences of the electric capacity and conductivity of the films; the optical absorption and reflection spectra were also studied. It was concluded that the samples contained a ferroelectric phase. The structure of the films was studied by atomic force microscopy. As a result of the structural studies, the peculiarities of the temperature dependences of conductivity and capacity, in particular, the temperature range in which the phase transition was observed were explained.

Langmuir films of various thicknesses, fabricated based on liquid crystals, have been studied. Previously, a structural phase transition at a temperature of ∼75°C was detected for these films. To determine the nature of this transition, the temperature dependences of the capacitance and conductance of the metal-Langmuir film-metal structures have been measured. The results obtained suggest that the ferroelectric phase in the studied samples exists beginning with one monolayer. The length of the temperature interval in which the phase transition is observed indicates a film structure imperfection.

The temperature dependences of diffuse reflection spectra and the polarization of light reflected from ultrathin Langmuir films based on liquid crystals are studied. The results are compared to the experimental data obtained on thicker liquid films. The dependences of the electric capacity of metal-film-metal structures on temperature are measured. The maximum for ultrathin films lies near 75°C, indicating the occurrence of a ferroelectric phase transition. Features in the intensity and polarization of the reflected light are registered at the phase transition temperature. It is concluded that the generality of the results obtained using samples of both types indicates the existence of a mesomorphic phase in Langmuir films. The observed differences could be associated with either dimensional effects or differences in the structures of the films.

The adsorption isotherms of water molecules, absorption spectra, and spectra of diffuse scattering and polarization of reflected light are studied for ultrathin Langmuir films prepared based on liquid crystals. A structural phase transition near 70°C is detected. Some specific features of the reflection spectra at the phase transition temperature are found. Suggestions are made regarding the nature of the phase transition.

The isotherms of water molecule adsorption and the spectra of absorption, diffusion reflection, and polarization of reflected light for hyperfine Langmuir films that were fabricated based on liquid crystals are investigated. Singularities in the reflection spectra at the temperature of the structural phase transition (∼70°C) are revealed. Some reasonable assumptions on the nature of the phase transition are made.

This paper studies the influence of adsorption of methanol and iodine molecules on the conductivity of para-tetradecyloxybenzyliden-amino-2-methylbutyl-cyanocinnamate that was obtained using the Langmuir-Blodgett method. The growth of conductivity of the studied films at methanol absorption and the reduction of conductivity upon iodine absorption was discovered. An explanation of the observed conductivity variation at adsorption is proposed.