Liquid Crystals as Lubricants

Abstract

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.