Carbohydrates as Inducers in Cholesteric Lyotropic Mesophases

Abstract

The use of sugars as chiral dopants for cholesteric lyotropic mesophases preparation is reported. Several aldo-hexoses (D-mannose, D-glucose and D-galactose), a keto-hexose (L-sorbose) and a disaceharide (D-sucrose) were added to mesophases prepared from potassium laurate (KL). The resulting cholesteric phases correspond to Ch_D systems. Carbohydrates as highly hydrophylic solutes have a very low twisting power. Only at sugar concentrations higher than 2% (molar fraction), detectable pitches can be obtained and directly measured from the polarizing microscope textures. Even in the concentration range where a measurable pitch is not observed, it is possible to characterize the optical activity at the polarizing microscope. These studies show that sugars are able to induce cholesteric lyomesophases however low twisted. The optical activity measurement amplifies the cholesteric characterization towards long pitch systems.