Curcumin-Encapsulated Hexagonal Liquid Crystalline Formed by Brij 97/NaDC Mixtures

The phase diagram of a five-components Brij 97-NaDC/IPM-PEG 400/H₂O system was determined at 25°C. The hexagonal liquid crystalline phase (H₁) was found in this system. By use of small-angle x-ray scattering (SAXS), polarization microscopy, and rheology techniques, the influence of composition, temperature, and addition of curcumin on H₁ phase was studied. It is shown that: 1) the investigated hexagonal liquid crystals exhibit a strong shear thinning behavior and viscoelasticity and the strength of the network of H₁ phase becomes weaker with increasing oil content; 2) the frequency-dependent moduli of H₁ samples decreases as the temperature increases and the steady-state limiting viscosity of the hexagonal samples shows an Arrhenius-like dependence on temperature; and 3) samples in H₁ phase containing curcumin retained their organized hexagonal structure. The SAXS results show that the curcumin molecules may be solubilized both into the apolar core of cylinders together with IPM and in the polar domain coexisting with PEG 400 between the cylinders. When curcumin is encapsulated in samples with low oil content, there is a significant decrease in the frequency-dependent moduli. The tendency of frequency behavior for samples incorporating curcumin as a function of temperature is weakened.