sulphate head groups are represented by a smeared out, evenly distributed surface charge located at, or somewhat outside, the hydrocarbon-water contact interface. Furthermore, the counterions are, as a rule, treated as point charges. The packing of the hydrocarbon chains and the accumulation of counterions give rise to a surface pressure that counteracts the interfacial tension of the hydrocarbon-water interface (≈50 mJ m ).

doi:10.1201/9780203021262-179

Chapter

sulphate head groups are represented by a smeared out, evenly distributed surface charge located at, or somewhat outside, the hydrocarbon-water contact interface. Furthermore, the counterions are, as a rule, treated as point charges. The packing of the hydrocarbon chains and the accumulation of counterions give rise to a surface pressure that counteracts the interfacial tension of the hydrocarbon-water interface (≈50 mJ m ).

Chapter

ABSTRACT

As the whole of a surfactant micelle has the intrinsic nature of an interfacial complex, we must assume, of course, that the pressure within the hydrocarbon core varies from point to point, and is generally anisotropic, except at the very center, implying that the pressure tensor components PT and PN in the tangential and normal directions, respectively, are, as a rule, different. Thus, there is no natural definition of Pi. Nonetheless, it turns out to be convenient to put Pi equal to the average tangential pressure within the micelle core, that is,

(211)

Accordingly, the core contribution to γ will vanish, yielding simply:

(212)

On the other hand, in terms of γ and πc, the work of forming a spherical equilibrium micelle at fixed chemical potentials is found to be given by the expression (Eq. (158)):

(213)

that is necessarily invariant with respect to both the choice of dividing surface as well the internal reference pressure.