Effect of Metal-Oxide Nanoparticles on the Viscosity of Lamellar Liquid Crystals in the Lecithin–Oil Mixture–Water System

It is shown that the viscosity of lamellar liquid crystals in the system lecithin–avocado oil–tea tree oil–water in the shear rate range of 0.01–1.0 s^–1 increases with increasing CuO concentration from 0.01 to 0.3 wt % when introduced as spherical nanoparticles with a diameter of 92 ± 3 nm and submicron cylindrical particles with a diameter of 151 ± 9 nm and a length of 268 ± 36 nm, while the shape of the flow curves does not change. The range of changes in the viscosity (compared to the sample without particles) at temperatures of 25 and 37°С is from 1.1 to 2.1 times for spherical nanoparticles and from 1.6 to 2.9 times for submicron cylindrical nanoparticles. When introducing spherical Al₂O₃ nanoparticles with an average diameter of 84 ± 32 nm and needle-shaped ZnO nanoparticles (diameter 37 ± 6 nm and length 302 ± 77 nm), similar results are obtained: the viscosity increased by 1.1–2.0 times compared to the sample without nanoparticles. In contrast to nanoparticles, the introduction of CuO microparticles (diameter 31.2 ± 3.6 μm) has virtually no effect on the viscosity of the composition.