Interfacial phenomena free energy

The advantage of measuring the effect of a surfactant in an interfacial phenomenon by some parameter that is related to the standard free energy change associated with the action of the surfactant in that phenomenon is that the total standard free energy change can be broken into the individual standard free energy... 

It may be added here that the four basic laws of capillarity, i.e., the equations of Gibbs [(10.2)], Laplace [(10.7)], Kelvin [(10.9)] and Young [(10.10)], all describe manifestations of the same phenomenon the system tries to minimize its interfacial free energy. (Another manifestation is found in the Hamaker equations see Section 12.2.1.) These laws describe equilibrium situations. Moreover, dynamic surface phenomena are of great importance. 

Partial Coalescence. This is a complicated phenomenon. It can occur in O-W emulsions if part of the oil in the droplets has crystallized. The ultimate driving force is, again, a decrease in interfacial free energy, but the relations given by Hamaker, Laplace, and Young (Section 10.6.1) all are involved. 

Besides coalescence, there is another mechanism by which emulsions degrade (or coarsen) into fewer, larger-sized droplets diffusional degradation. Monomer from smaller droplets diffuses to larger ones as the result of the process of interfacial free energy minimisation. This phenomenon is called Ostwald ripening (224). 

Therefore, the use of surfactants for the modification of interfaces is very versatile, both with respect to the nature of the interfaces (between solid and liquid, polar and nonpolar), as well with respect to the assortment of the available surfactants. Up to this point, we have been talking about amphiphilic synthetic organic surfactants. However, the adsorption phenomenon is universal in nature and industry and takes place at all interfaces without any exceptions. It is worth emphasizing one more time that the general reason for the accumulation of surface-active substances at interfaces is the lowering of free energy as a result of the partial compensation of the disrupted bonds between interfacial atoms. 

The experiment clearly demonstrates the phenomenon of interfacial melting, the viscous nature of the premelted liquid and its dynamical consequences. Initially the observed relative lack of membrane deformation at lower temperatures was thought to be due to an abrupt jump to 0. Such an interpretation is consistent with an interfacial free energy that decreases monotonically with d at long range, but which possesses a local minimum at shorter range. The theory has allowed us to show that the... 

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