Micellar colloids, conductance

Ionic micelles will migrate in an electric field, and the ion atmosphere of the colloidal particle is dragged along with it. Interpretation of micellar mobility (conductivity experiments) must take this into account. The same is true, however, of the mobility of simple ions, but the situation is more involved here since the micelle and the ion atmosphere have comparable dimensions. We see in Chapter 12 how particle and double-layer dimensions affect the interpretation of mobility experiments. 

Indeed, much higher levels of conductance fluctuations were reported for electrolytes that contain polystyrene latex suspensions (21) or micellar colloids (22). Fluctuations were shown to depend on concentration, characteristic size, and the charge of colloid particles. For uncharged nonconductive spherical particles that occupy volume fraction F of the total sample volume... 

Paul, B.K. and Mitra, R.K. 2006 Conductivity of reverse micellar systems of water/ AOT + Brij-56 or Brij-58/lPM and their percolation under varied concentrations of amphiphiles and different additives. Colloids Surf., A 273 129-140. 

The thermodynamic equilibria of amphiphilic molecules in solution involve four fundamental processes (1) dissolution of amphiphiles into solution (2) aggregation of dissolved amphiphiles (3) adsorption of dissolved amphiphiles at an interface and (4) spreading of amphiphiles from their bulk phase directly to the interface (Fig. 1.1). All but the last of these processes are presented and discussed throughout this book from the thermodynamic standpoint (especially from that of Gibbs s phase rule), and the type of thermodynamic treatment that should be adopted for each is clarified. These discussions are conducted from a theoretical point of view centered on dilute aqueous solutions the solutions dealt with are mostly those of the ionic surfactants with which the author s studies have been concerned. The theoretical treatment of ionic surfactants can easily be adapted to nonionic surfactants. The author has also concentrated on recent applications of micelles, such as solubilization into micelles, mixed micelle formation, micellar catalysis, the protochemical mechanisms of the micellar systems, and the interaction between amphiphiles and polymers. Fortunately, almost all of these subjects have been his primary research interests, and therefore this book covers, in many respects, the fundamental treatment of colloidal systems. 

The electrical conductance of a colloidal solution can be considered to be built up from contributions of the colloidal particles and the ions present in the solution. In a xnore schematic way the conductivity can be split up into a contribution of the sol particles and their counter ions (micellar conductivity) and a contribution of the rest of the liciuid (intermicellar conductivity). This second method is mostly used in the practice of conductance measurements of colloids, but it should be realised that it is less exact than the first onc In the first place it is rather arbitrary to denote a certain part of the positive ions (the particles are supposed to be negatively charged) as counter ions and the rest of them as belonging to the intcrmiccllar liquid. Moreover it neglects all interaction between the sol particles and the intermicellar ions, which is often not allowed. 

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