COLL 5 |
| Gordon J.T. Tiddy, Chemical Engineering, Chemical Engineering, UMIST, Manchester, Department of Chemical Engineering, UMIST, Manchester, M60 1QD, United Kingdom |
| Gel phases occur very commonly in many commercial and natural surfactant (lipid) systems. They are mono- or bilayer states where the alkyl chain packing has far more order than in the lamellar phase. Usually they are treated as equilibrium structures at formation, or very shortly thereafter (within mins). However, when they are used for practical applications such as in emulsions and conditioners, the products often undergo changes in properties over a period of hours to days. Very little is known in detail about these changes, but given the wide range of alkyl chain configurations that can occur in the gel phase, perhaps they should be regarded as the norm rather than the exception. A simple consideration of Ostwald's Law of stages1 suggests that this is so. This contribution will review our recent research on this area, including surfactant specific electrode studies that show remarkable non-equilibrium effects on dilution2 We now have found that these last for weeks. It will also describe related X-ray diffraction and rheology studies, carried out on commercial and natural surfactant systems. Very recent results arising from studies on bacteriocide formulations indicate the presence of lipids in a gel state within membranes of bacteria in vivo. |
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ACS Award in Colloid and Surface Chemistry Symposium Honoring Clay Radke
Division of Colloid and Surface Chemistry |