We review the interesting physical effects arising when bifunctional molecules, consisting of two moieties, one polar and the other apolar, are dissolved in a simple solvent. The peculiarity of such amphiphilic molecules is that they generate by themselves confined structures in which they are embedded and of which they dictate the topology according to their aggregative properties. Individual molecules are still free to redistribute within or across the aggregates. When two or more types of amphiphilic molecule are mixed together, the strong coupling between local interactions and the aggregate topology gives experimental access to a variety of non-ideal mixing effects. The couplings between the lateral distribution and the geometrical features of amphiphile assemblies are discussed separately for monolayers, bilayers, multilayers, and micelles. Concentration and temperature effects are taken into account. The case of non-ideal mixing of chemically identical molecules with mutually interchanging conformations is also discussed. It is found that bistability and thermal hysteresis phenomena can be important. Theoretical arguments are supported by a variety of experimental observations made of a class of amphiphilic molecules, the gangliosides, which are particularly suitable subjects for investigation as regards such non-ideality effects. Gangliosides, with a double-tail hydrophobic part, like phospholipids, and a bulky saccharidic headgroup, show relevant like-like and like-unlike interactions, and easily form large aggregates whose topology is quite sensitive to monomer redistribution.
|Titolo:||Physical aspects of non-ideal mixing of amphiphilic molecules in solution|
|Settore Scientifico Disciplinare:||Settore FIS/07 - Fisica Applicata(Beni Culturali, Ambientali, Biol.e Medicin)|
|Data di pubblicazione:||1997|
|Appare nelle tipologie:||01 - Articolo su periodico|