Physical Properties of Surfactants

The hydrophile-lipophile balance (HLB) system is the measure of the surfactant s polarity as well as other physical properties of surfactants and the emulsifying materials. The more lipophilic the surfactant is, the lower the HLB values will be. Table 4.5 empirically classifies and compares surfactants according to their optimum use. Table 4.6 shows the HLB values for a selected group of surfactants. The HLB value of the surfactant or surfactant mixture should be matched with that of the oil or the mixture of oils to ensure a stable emulsion. The required HLB values of a... 

An early attempt to correlate the physical properties of surfactant solutions and their foams with oil recoveries was performed by Deming in 1964 (50). Deming concluded that high foaming ability favored high displacement efficiency, but that high foam stability were not required for high displacement efficiency. Bernard and Holm found that oil substantially decreased the abilities of most surfactants to reduce aqueous permeabilities, but that some surfactants remained effective even in the presence of oil (52,53). 

We are now interested in the structure and physical properties of surfactant monolayers at LL and LG Interfaces. The primary physical characteristic is y. Let us first consider equilibrium states. Then, y can be related to the composition of the solution via Gibbs law. 

Evans, E. and Needham, D. (1987) Physical properties of surfactant bilayer membranes-thermal transitions, elasticity, rigidity, cohesion, and colloidal interactions. Journal of Physical Chemstry, 91 (16), 4219 228. 

This approach is based on the use of the unique physical properties of surfactant molecules in aqueous solutions, which n es it possible to electropolymerize thiophene derivatives and to study the influence of micelles on the electropolymerization process and on the structures and properties of die resulting polymer films. 

The spontaneous self-assembly of surfactants is an active area of research in part because weak interactions in solutions of ionic surfactants depend on both ion type and charge and these ion specific effects alter, sometimes dramatically, the chemical and physical properties of surfactant solutions. However, consensus is absent on how to model these effects. In modem science terms this is an ancient problem because specific ion effects of surfactants solutions, proteins and biomembranes have been known for... 

The above introduction illustrates the role of surfactants in various agrochemical formulations. It is necessary to know the physical properties of surfactants, their adsorption at various interfaces and their phase behaviour. These topics are dealt with in Chapters 2 to 5. The role of surfactants in stabilisation of emulsions and suspensions is been dealt with in detail in Chapters 6 and 7. 

---