Inducer Chemical Nature and the Helical Twist Sense of Cholesteric Lyotropic Mesophases

Abstract

In the present work, helical twist senses for induced cholesteric lyotropic liquid crystals are determined. Several chiral inducers able to locate at different mesophase environments were added to lyomesophases bused on the amphiphiles decylammonium chloride, potassium laurate, sodium and cesium decylsulphate, sodium dodecylsulphate and potassiam decanoate. Polarizing microscopy techniques used for thermotropic cholesteric twist sense determination were extended to lyotropic systems. Only when the inducer remains predominantly in the bulk water its structure plays an important role to establish the cholesteric twist sense. Hydrophobic inducers added to different systems lead to the same helical twist sense, since the paraffinic intra-micellar environment is essentially the same. By the other hand, hydrophilic inducers or hydrophobic solutes with ionizable groups subjected to strong interactions with the electrical double layer will originate cholesteric mesophases whose helical twist sense can be inverted by changes on the charge distribution of the micellar surface.

Key Words:

• lyotropic mesophases
• cholesteric mesophases
• cholesteric inducers
• optical activity in lyomesophases
• optically active amphiphiles
• lyotropic cholesteric twist sense