Characterisation of a new nematic lyotropic liquid crystal with natural lipids from soybean

Abstract

Searching for a lubricant to be used in articular bone joints, a new nematic liquid crystal (NLC) was characterised. It is formed by dissolving tetradecyltrimethyl ammonium bromide (TTAB), decanol (DeOH), sodium bromide (NaBr) and a natural mixture of lipids (PL, from soybean) in water. Small amounts of D O, and SDS-d were added as²H-NMR probes. The mesophases were characterised using²H-NMR spectroscopy, kinematic viscosity measurements, polarised light microscopy (PLM) and molecular dynamics (MD) simulations. The present system is suitable for lubrication applications, since the solution viscosity is tunable from 49 to 811 cp, more than twice the range previously obtained in a similar system. The solution contains an important proportion of a natural mixture of lipids extracted from soybean, enhancing biocompatibility. The wider range of viscosity displayed by this system, without losing the nematic phase, is attributed to the greater amount of amphiphiles supported by the solution and the size and elongation of the aggregates when the surface charge density is increased. This elongation represents a phase transition from a discotic monoaxial phase to biaxial phase and is responsible for the changes in quadrupolar splittings.