Effects of salts and structure of chiral dopants on the induced pitch from micellar nematic phases

Abstract

The effect of adding salt to three different micellar chiral nematic phases, and the effect of structure of two chiral dopants, hexahydromandelic acid (HHMA) and mandelic acid (MA), on two achiral nematic host phases have been investigated. The addition of salt to the chiral nematic phases increased the pitch length, and a further addition led to cholesteric–lamellar phase transition. This phase transition was explained as fusion of individual micelles to coherent but defect rich bilayers. The effect of the structure of HHMA and MA on decylammonium chloride (DACl) and DL-serine hydrochloride decyl ester (DL-SDE) reflected itself in three different phenomena. (i) HHMA elevates the cholesteric–isotropic phase transition temperature, whereas MA lowers it, in general. (ii) The HHMA caused a change in diamagnetic anisotropy of DACl system, but MA has no such effect. (iii) The β value of HHMA in DACl host phase was twice as large as that of MA, but it was only slightly different from that of MA in DL-SDE system. These phenomena and the chirality transfer were interpreted as a result of the shape of the chiral solute and solute–solvent interactions.