The microscopy of the liquid crystalline neat and middle phases of soaps and synthetic detergents

Abstract

Summary The mesomorphic or “liquid crystalline” neat and middle phases encountered in aqueous systems of soaps and synthetic detergents differ considerably in plasticity. Nevertheless, in fundamental phase studies or the examination of commercial products and processes, identification of these two phases has hitherto been uncertain, particularly when they are mixed with each other or with other phases; even under the polarizing microscope, their identification has not been positive since, by the classical criteria for identifying mesomorphic phases, both are “smectic.” The present work reveals additional criteria by which the two phases may be satisfactorily distinguished. In the first place, there are non‐geometric textures exhibited by middle but not by neat. Conversely, there are planar textures exhibited by neat but not by middle. Furthermore there are important systematic differences even among the focal conic textures upon which the smectic nature of the two phases has previously been predicated. While the microscopic method now makes possible the identification of phase mixtures, it serves also as a rapid method even where one‐phase compositions are concerned. This study is primarily descriptive in its present state of development, but the existence of systematic microscopic differences between these two nominally smectic phases, coupled with their well‐known and pronounced difference in consistency, suggests a fundamental structural distinction between them. Much of the present subject‐matter applies also to such materials as certain wetting agents and dyes, as well as phosphatides and certain other biological substances.

Supra-molecular Association and Polymorphic Behaviour In Systems Containing Bile Acid Salts

“…In polarised light, the birefringence of these samples is similar to that observed in diluted lyotropic liquid crystals, Figure 6. The optical anisotropic textures observed by optical polarising microscopy are reminiscent of those occurring in normal surfactants and lipids [85,86]. The phase behaviour of some binary aqueous BS mixtures of sodium deoxycholate, NaDC, NaGDC (sodium glycodeoxycholate) and NaTDC (taurodeoxycholate)-water systems is shown in Figures 7a-c.…”

Phase Behavior and Effect of Enantiomerism on Potassium N -Dodecanoyl Alaninate/Water/Decanol Systems

“…The L a phase is characterized by the SAXS pattern with q values at the ratio of 1 : 2 : ...., and oily streak texture (26 gates increases the aggregate size, which is reflected in the gradual increase in d observed inside the H 1 region.…”

Investigating reversed liquid crystalline mesophases

“…Methods, such as SAXS, can not distinguish between the Fd3 and Fd3m space group. NMR or polarized microscopy [9] can be used to establish the presence of isotropic and anisotropic phases. Borné et al [10] used deuterium single quantum NMR to establish the ternary phase diagram of D 2 Odiolein-monoolein.…”