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Authors
Affiliations
1 School of Physical Sciences, Jawaharlal Nehru University, New Delhi - 110 067, IN
Source
Journal of Surface Science and Technology, Vol 15, No 1-2 (1999), Pagination: 41-57
Abstract
Reverse micelles of Water-AOT-Isooctane have been studied for the Water/AOT concentration ratio, W0 varying from 1 to 50, by dynamic laser light scattering and capillary viscometry techniques in the AOT concentration range, 100, to 500 mM. The ratio of the rigidity of the interface, K-to that of effective surface tension, γ; (K/γ) defines a new length scale, ζ, (K/2γ) = ζ,2 = R0R where a reverse micelle of radius R is formed of surfactants having a spontaneous curvature 1/R0 We show that for W0 ≤ 20, the reverse micelles can be modelled as spheres purely from geometrical considerations and for W0 > 20, these conformationally resemble deformed spheres. Correspondingly, the relative viscosity of the solution, nr shows a micellar volume fraction dependence, , nr(φ) = (1-φm-λφ2)δ. For low AOT concentration (100 mM), δ = 2.52 5 ± 0.06 implying a near spherical shape for the micelles. This increased to δ = 2.91 ± 0.06 at the AOT concentration, 500 mM which we envisage as micelles having deformed spherical conformation. The micellar stability has been deduced from free energy calculations which yields an explicit expression for the pressure, P(R) inside the water core of a reverse micelle. The intermicellar interaction has been discussed within the frame work of short-range interaction potential and perturbation potential ∼r-6.
Keywords
Reverse Micelzes, DLS Stability, Conformation.
