Free energy of a charged surface

For small (or even moderate) surface potentials such that C can be approximated by Eq. [182], we can use Eq. [181] to find the electrostatic free energy of the charged surface according to Eq. [29]. Since the approximate solution [177] has the same form as the Gouy-Chapman solution for a plane and 8a, and hence is independent of the surface potential, the evaluation of the free energy follows that leading to the planar result of Eq. [30] in all details, and we can immediately write... [Pg.216]

The effect mentioned under (1) is important if we consider the case in which the charge of the particles is kept constant and the surface potential is a function of the distance of the particles (or plates). In that case no ionic transport from one phase to another occurs, and therefore no chemical effects are involved. Hence it appears that the fallacious results obtained in this case are entirely explained by the difference between field energy and free energy of the charges. Actually we find, for the two quantities, icntirely different relations behaving very differently as a function of the distance of the particles. [Pg.190]

Note that the polar vector reflects only polar symmetry of the interfacial layer and may be associated with the conical (not rod-like) form of the molecules. However, when the electric charges are involved in the game, the same polar order may results in appearance of the macroscopic surface electric polarization Psurf that is the dipole moment of a unit volume [units CGS(charge) cm/cm = CGSQ/cm = StatV/cm, or C/m in SI system]. When an electric field is applied to a liquid crystal the surface polarization contributes to the free energy of a surface layer... [Pg.266]

Surface chemistry is very important for the physiological interactions with biomaterials and it is closely related to surface energy (hydrophobicity) the surface free energy of a material originates from its surface functional groups and electrical charges. The material s surface chemistry mediates cell response given that surface... [Pg.107]

A general prerequisite for the existence of a stable interface between two phases is that the free energy of formation of the interface be positive were it negative or zero, fluctuations would lead to complete dispersion of one phase in another. As implied, thermodynamics constitutes an important discipline within the general subject. It is one in which surface area joins the usual extensive quantities of mass and volume and in which surface tension and surface composition join the usual intensive quantities of pressure, temperature, and bulk composition. The thermodynamic functions of free energy, enthalpy and entropy can be defined for an interface as well as for a bulk portion of matter. Chapters II and ni are based on a rich history of thermodynamic studies of the liquid interface. The phase behavior of liquid films enters in Chapter IV, and the electrical potential and charge are added as thermodynamic variables in Chapter V. [Pg.1]

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