Molecular Crystals and Liquid Crystals, Vol.378, 89-101, 2002
The effect of water on the flow orientation process of lyotropic liquid crystals cholesterized by D(+)-mannose
The rheological behavior of cholesteric lyotropic liquid crystals can give information about the chiral forces involved in the formation of the cholesteric arrangement. In the present work, we studied the effect of water availability on the orientation process of a lyotropic liquid crystal system submitted to flow. Different mesophases based on decylammonium chloride were prepared with different amounts of D(+)-mannose added as inductor. It was observed that the flow orientation process on cholesteric lyomesophases is different when occurring in a room atmosphere or a water-saturated atmosphere. For samples sheared in a room atmosphere, the orientation process involves an initial step of destruction of the cholesteric structure caused by shear, leading to the formation of microdomains with different orientations. In a second stage these microdomains orient themselves, forming a new helical structure in the flow direction. When the systems are sheared in a water-saturated atmosphere, the orientation process involves the accommodation of micelles into a new structure seeking the best orientation in the flow direction.