Emulsions mesomorphic phases

The most frequently discussed topic in washing is the role of solubilisation processes. Many investigators [76] attract attention to the fact that the surfactant concentration in a washing solution is much lower than CMC, and in this connection, solubilisation of oils is principally excluded due to absence of surfactant micelles. At the same time, the review of recent works [85, 86] show that solubilisation can play a dominant role both in washing fabrics and in the removal of soils from solid surfaces. These views are based on the following mechanisms. Surfactants adsorb at w/o interfaces under formation of densely packed adsorption layers which leads to a high local surfactant concentration as compared with the rather low concentration in the washing solution. After that, noticeable penetration of water into the oily soil is possible, under formation of liquid-crystal phases. Then, mesomorphic phases are swelled and destroyed under the formation of emulsion droplets. 

The results presented show that using simple methods and materials, it is possible to demonstrate the formation of associated structures and their role in easy emulsion formation. Similarly the part played by reduction in interfacial tension has been presented. The stability of these emulsions in relation to the type and extent of formation of the mesomorphic phases is being investigated and will be the subject of a future communication. 

Friberg and his co-workers have drawn attention to the importance of mesomorphic phases to emulsion stability (e.g. [86,87]). Fig. 8.15 shows a simplified phase diagram for an oil-water emulsifier in which the region of the mesomorphous phase (C) is shown. When the concentration of emulsifier is increased to the point where the composition of the system passes from the two-phase area A + B to the three-phase area A -h B -h C the stability of the emulsion increases suddenly and the viscosity rises. Both of these changes are due to mesophase C distributed in solution B which is the continuous phase of the... 

Amphiphilic lipopeptides with a hydrophobic paraffinic chain containing from 12 to 18 carbon atoms and a hydrophilic peptidic chain exhibit lyotropic meso-phases and good emulsifying properties. The X-ray diffraction study of the mesophases and of dry lipopeptides showed the existence of three types of mesomorphic structures lamellar, cylindrical hexagonal and body-centred cubic. Two types of polymorphism were also identified one as a function of the length of the peptidic chain and the other as a function of the water content of the mesophases. The emulsifying properties of the lipopeptides in numerous pairs of immiscible liquids such as water/ hydrocarbons and water/base products of the cosmetic industry showed that small amounts of lipopeptides easily give three types of emulsions simple emulsions, miniemulsions and microemulsions. 

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