Glycerol Effect on the Microstructure and Rheology of Lyotropic Liquid Crystals Formed in Sucrose Laurate/Glycerol/Water Systems

To investigate glycerol effect on the microstructure and rheology of lyotropic liquid crystals formed in sucrose laurate/glycerol/water systems, a series of pseudo-ternary surfactant system are prepared and investigated. SWAXS data confirms the presence of hexagonal liquid crystal phase (H₁ phase) as the predominant phase in sucrose laurate/water systems with a medium-to-high surfactant concentration. These changes in SAXS pattern demonstrate that glycerol incorporation into aqueous phase in sucrose laurate/water system would reduce the long-range positional ordering of cylindrical micelles in H₁ phase, even results in a transformation of H₁ phase to other disordered phases. Moreover, the effect gradually diminishes with growing surfactant content but still remains in these systems. However, The WAXS profiles indicate that the short-range order of hexagonal liquid crystals is also affected by the glycerol addition. These conclusions are corroborated by polarized light microscope observations and subsequent rheological tests. Variable-temperature SWAXS experiments show that glycerol incorporation significantly reduces the critical temperature where a drastic decrease in the long-range positional ordering of the H₁ phase occurs. Steady shear rheology confirms that glycerol incorporation leads to a decrease in the structural ordering of H₁ phase. Dynamic frequency sweep experiments indicate the strength or stiffness of the liquid crystals decrease with the addition of glycerol. However, these effects become less pronounced with the increase of surfactant content.