Detergency mesophases

Comparson of the transitions observed by differential scanning calorimetry in membranes of M. laidlawii and in water dispersions of the lipids from the membranes support the concept that most of the lipids exist as a smectic mesophase in the membranes. The evidence for a bilayer structure is straightforward in this case. Lipid transition temperatures are a function of fatty acid composition and correlate well with biological properties. The calorimeter possesses advantages over high resolution NMR for M. laidlawii, and perhaps in many other systems, because the data can be interpreted less ambiguously. In M. laidlawii membranes the bilayer appears to be compatible with the same physical properties observed in other membranes—a red-shifted ORD, lack of ft structure in the infrared, reversible dissociation by detergents, and poorly... 

LC polymers can either be thermotropic, their LC phases or mesophases are formed by heating a solid or cooling a liquid or solid, or lyotropic, the mesophases are formed by association of molecules in solution. The photochemistry and photophysics of molecules in lyotropic phases such as detergent micelles and lipid bilayers has been a very active research area for about 30 years. This extensive literature [12] is not reviewed in this chapter which is necessarily restricted to thermotropic LC polymers. 

Ai, X., Caeerey, M., Membrane protein crystallization in lipidic mesophases Detergent effects. Biophys. J. 2000, 79(1), 394-405. 

Rheology is increasingly being coupled to other analytical test methods for more comprehensive material characterizations. Many of these developments are driven by research needs for broadened characterization capability. For fundamental studies of detergent systems this offers a broad suite of methods to probe surfactant mesophases and internal microstructure. 

Over the past few decades there has been an increase in the research tools for fundamental rheology studies of surfactant solutions and commercial detergent formulations. The coupling of rheometers with other methods has broadened the range of studies that can be completed, leading to a better understanding of solution properties, self-assembled mesophases, multiple-component dispersions, and gels. 

Oily soils containing amphiphilic species, such as fatty acids or fatty alcohols, can also be removed from substrates as a result of the formation of liquid crystal or mesomorphic phases between the amphiphile and a detergent. The liquid crystals are then broken up by subsequent osmotic penetration by water [140-142], Removal of solid soils by mesophase formation can be accelerated by increasing the temperature. This has been reported for stearyl alcohol [143] and for lauric, palmitic, and stearic acids [128, 129] and is likely due at least in part to the increased penetration of the soils at higher temperatures [128,129,143],... 

An examination of the composition and physical state of sebum suggests that several cleaning mechanisms can operate during its removal from hair. Since sebum is completely molten at body temperature [122], it can be effectively removed by the roll-back mechanism. Also, the presence of approximately 25% free fatty acids in sebum indicates, as discussed in Section IV.C.3, that it is subject to removal by emulsification and mesophase formation. Finally, because the concentration of detergents during shampooing is well above their critical micelle concentrations, sebum can also be cleaned from hair by solubilization. 

It is understood that manufacturing of liquid detergents that are unstructured in their commercial form may involve intermediate streams which are, in fact, structured fluids, such as surfactant solutions at high active concentrations, within anisotropic mesophase boundaries, or concentrated polymeric solutions and gels. Whether the source is raw material, premix, or final product, manufacturing operations for each of these classifications are discussed with a focus on any specific requirements or limitations due to the physicochemical form. 

The lyotropic behavior of these carbohydrate derivatives has been studied very carefully [96]. It follows the classical sequence of mesophases established for the ionic detergents such as soaps. In contact preparations of l-0-octyl-/3-D-glucopyranoside (10 e) with water at room temperature three types of lyomesophases are observed (from high to low amphiphile concentration) lamellar, cubic and columnar hexagonal, their principal structures are depicted in Fig. 12. 

From a historical point of view as well as due to their applications, thermotropic and lyotropic liquid crystals have always been treated separately. While thermotropics and the concept of liquid crystallinity in general were discovered as late as in 1888 [3], lyotropic phases were known to mankind since the Bronze Age [4], as they occur during the soap-making process. Due to this, lyotropic liquid crystals find their main applications in the detergent industry and in cosmetics. As various biological systems, e.g. cell membranes, take a lyotropic liquid crystalline form, they also possess some medical and pharmaceutical importance [5]. In contrast, thermotropic liquid crystals are used for completely different applications, e.g. for displays, thermography, tunable filters or lasers [6]. Thus, it is not astonishing, that two distinct fields of research evolved for the two types of liquid crystals. However, thermotropic and lyotropic liquid crystals share a common state of matter with many similarities. For example, many mesophases which occur in thermotropics can also be found in lyotropics. Still, there are some thermotropic phases which do not seem to have a lyotropic counterpart. 

Other related amino-acid derivatives have similar N values. Spectrum measured of radical immobilised in bovine opsin and in solution in detergents. Several related radicals reported. ) Measurement of rotational correlation times in the presence of HoC6H4CH2N H2C6HiiX . Measurements in several liquid crystal mesophases both stereoisomers examined. ... 

Note that this phase sequence, can be universally observed in the thermotropic phase sequence of block copolymers and low-molecular-mass amphiphiles as well as in lyotropic detergent solvent systems. In addition to the phase sequence described above, several additional intermediate phases can occur at the transitions between different mesophase morphologies. The bicontinuous cubic phases Cub are often also included in these intermediate phases. 

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