Phase Behavior and Rheological Properties of Concentrated Lecithin Aqueous Solutions with Additives

Lyotropic Liquid Crystal Formed in Aqueous Lecithin Solutions with IPM and AEO20 Additives

The phase behavior and rheological properties of a lyotropic liquid crystal formed in the lecithin/AEO20/IPM/H2O system were investigated by means of phase diagram, polarized optical microscopy and rheology techniques at 37°C. After adding polyoxyethylene-20-oleyl ether (AEO20) and isopropyl myristate (IPM) to lecithin solutions, an isotropic liquid phase and an anisotropic liquid crystal phase were found. By analyzing the shear viscosity (η γ=0.1) and yield stress (σ 0), with increase in water content, the η γ=0.1 and σ 0 increase firstly and then decrease; with increasing IPM content, a decrease in the η γ=0.1 and σ 0 is observed. Notably, at the relatively higher water content area, the water content has little effect on the η γ=0.1 and critical stress. When the lecithin/AEO20 mass ratio is 1:2, the liquid crystal phase displays a stronger shear resistance and more stable network structure.