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

Mass density measurements as a tool to distinguish between micelle size and shape in nematic and chiral nematic phases

“…The different effect of the structure of some solute molecules was discussed in terms of the pitch induced in some host phases 12,13 and by measuring the mass density. 14 In the latter case, the mass density of two chiral dopants, mandelic acid (MA) and hexahydromandelic acid (HHMA), were measured in two different host phases and it is found that the chiral phases containing MA were more dense than those containing HHMA. 14 The density changes can be thought to arise from the contribution of the two parts of the solutes, the hydrophilic and the hydrophobic parts, phenyl and cyclohexyl, respectively.…”

“…14 In the latter case, the mass density of two chiral dopants, mandelic acid (MA) and hexahydromandelic acid (HHMA), were measured in two different host phases and it is found that the chiral phases containing MA were more dense than those containing HHMA. 14 The density changes can be thought to arise from the contribution of the two parts of the solutes, the hydrophilic and the hydrophobic parts, phenyl and cyclohexyl, respectively. For instance, the solutes, MA and HHMA, to some extent, will become ionised in the micelle which can alter the counter-ion composition and hence the micelle size.…”

“…Indeed, in the previous communication some solutes were chosen and their mass densities were measured. 14 However, the density measurements were not complete and not discussed in detail and particularly the questions raised above were not answered. In order to have a clear picture of the effect of the structure of the solute molecules on the micelle size, it is important to study simple molecules from which the outcome may easily be perceived.…”

“…In a recent communication it was shown for one example that the mass density has increased as the racemic amphiphile (DL-SDE) in the racemic nematic phase was replaced by its L-enantiomer (L-SDE). 14 It is of fundamental interest to show whether this result can be generalized. Having been motivated by this aspect, and because there is very small choice on racemic/enantiomer amphiphiles we have synthesized amphiphilic molecules as decylesters and dodecylesters of the amino acids, alanine and serine.…”

“…In a recent communication we have shown for the first time, by a few examples, that mass density measurements may be used to detect relative changes in micelle size and micelle shape in a racemic nematic/L-isomer mixture and we have delivered some qualitative results on the effect of solutes on the host phases. 14 The present investigation is designed to show (i) quantitatively the effect of specifically chosen achiral solutes on the micelle dimension of the host phase, (ii) to extend the studies of racemic nematic/L-isomer mixtures to newly developed racemic nematic phases and their enantiomers and discuss why intrinsically chiral micelles can have smaller or larger densities than their racemic micelles. Furthermore, we will show, in contrary to common belief, that a distinction between induced chiral nematics and intrinsic chiral nematics is possible.…”