Influence of Plasma Chemical Treatment of Metallo-Mesogenic Discotic Compounds on their Physico-Chemical Properties

Abstract

The results of experimental studies of physico-chemical characteristics of metallo-mesogens – copper carboxylates after plasma chemical treatment in the glow discharge plasma of air are presented. After such treatment, the more intense change in the characteristics of the IR spectra was noted in the region of 1400–1600 cm –1 , which is characteristic of oxygen-containing groups. According to polarizing optical microscopy, the decrease in the interval of the columnar mesophase existence is observed for myristate by 17  C, for stearate –by 11  C, and for copper behenate – only by 5  C. This decrease can be explained by a significant screening of carboxylate surface at increasng of the hydrocarbon chain length. On the whole, the plasma-chemical treatment of copper carboxylates did not result to loss of liquid-crystalline properties. The most resistant to such effects was copper begenate, which preserved its thermal and mesomorphic properties practically without changing. The plasma-chemical treatment of copper carboxylates showed a positive effect on tribological (antifriction and anti-wear) properties of lubricants on addition of such metallomesogens to them. It was noted that the friction coefficient was decreased by 1,5–1,9 times and wear of samples was reduced by 1,14–2,0 times. The best tribological performance was observed for lubricants with the addition of plasma pretreated copper behenate. The presented studies make it possible to recommend plasma-chemical treatment in the glow discharge plasma of air to improve tribological characteristics of metal-mesogenic copper carboxylate additives.