Strange mass density behaviour of a micellar chiral nematic phase composed of an amphiphilic racemic mixture and its L-enantiomer

Abstract

Starting from the achiral nematic phase composed of DL-serine hydrochloride decylester (DL-SDE), the change in density has been measured at 20°C as DL-SDE was stepwise replaced by the L-enantiomer. It was found that the density increased linearly with the replaced mole fraction of the L-isomer. The average difference between the densities of the achiral nematic phase and intrinsic cholesteric phase was 0.001 g cm⁻³. In addition, the density of two chiral solutes, hexahydromandelic acid (HHMA) and mandelic acid (MA) was measured in DL-SDE and decylammonium chloride (DACl) achiral nematic phases, respectively. Using a constant composition of the phases and equimolecular amount of the chiral solutes, the density of the phases containing HHMA was smaller than those containing MA. The average density difference was larger in the DL-SDE phase (0.0025 g cm⁻³) than in the DACl phase (0.0017 g cm⁻³). These phenomena are novel and have been initially recognized by density measurements.