The effect of the cholesteric structure on the water activity of lyotropicliquid crystals

The study of the water activity behavior on liquid crystals is reported for lyomesophases based on sodium dodecylsulphate (SLS), decylammonium chlorid e (CDA) and potassium laurate (LK). Different amounts of chiral solutes (su gars or cholesterol) were added to the nematic matrices in order to form th e helical structure characteristic of the cholesteric system. The water act ivities of all mesophases were measured in order to evaluate how the water availability of lyomesomorphic systems is affected by the formation of the helical structure. It was verified that the helix formation on CDA system l eads to a decrease of the intermicellar forces driving to a situation where the water is less tightly bound. Seemingly, after an initial cholesterizat ion, the micelle-solvent interaction increases with the cholesterol concent ration. For systems based on SLS the formation of the helical structure lea ds to a condition where the water molecules are more tightly bound and, aft er an initial cholesterization, the micelle-solvent interaction does not ch ange with the further addition of inductor. For the LK systems it could be observed that a decrease of the water activity occurs only when hydrophilic inductors are added. LK systems present a rate of loss of water significan tly larger than the CDA.