Liquid Crystals as Lubricants

The review summarizes the literature data and the authors’ own research results on the application of liquid crystals in tribology. It has been shown that both thermotropic (calamitic, discotic, cholesteric) and lyotropic (surfactants, chromonics) mesogens as tribological additives are able to optimize the properties of lubricating compositions when introduced even at low concentrations to oils and greases. A wide possibility of varying the chemical structure of mesogens and studying the relationship between their structure and tribological properties can be used for the desired (programmed) change of the quality of tribotechnical processes. The synergism of the combined use of mesogenic esters of cholesterol and carbon nanostructures as additives in improving tribological properties has been established. The use of synthetic lubricants in biological systems still requires further research as the experimental results obtained on models of joint prostheses in vitro conditions are significantly worse than the results obtained in vivo. Considering the annual loss of billions of US dollars worldwide due to the low efficiency of friction processes in the industry and the resulting wear, liquid crystals and the systems based on them can be the most effective way to optimize these processes. The present review will be useful for researchers and industrialists

Floating layer structure of mesogenic phthalocyanine of A3_3B-type

To design efficient thin-film materials for low cost organic nanoelectronic devices, the Langmuir floating layer structure of the mesogenic 1,4,8,11,15,18-hexaoctyloxy-22,23,24,25-tetrachlorophthalocyanine (A3B-type) was characterized by Brewster angle microscopy, grazing incidence diffraction, and reflectometry. Starting from the area per one molecule of 7.6 nm$^2$, a single two-dimensional ordered structure with the period of 2.3 nm was formed. When the area reaches the value of 2.5 nm$^2$, a stable bilayer structure with imperceptible number of 3D aggregates was detected, in which each monolayer preserved organization of the preceding monolayer