ENERGY OF NONHOMOGENEOUS BENDING OF SURFACTANT MONOLAYER - PERSISTENCE LENGTH

We have considered the energy, g(nh), of a surfactant monolayer related to the gradient of its curvature. Taking into account this energy, we have determined the persistence length of the monolayer. Using the theoretical results, we have analyzed the experimental data presented in ref 11 for four kinds of surfactants forming microemulsions. The energy g(nh) is proportional to squared gradient of curvature. The important factor determining the value of this energy is the position of the neutral surface of the monolayer. The value of g(nh) is proportional to the fourth power of the distance-eta-0 between the neutral and the hydrophilic surfaces of the monolayer. The analysis of the experimental results of ref 11 showed us that in the frames of the developed approach we are able to explain the measured values of persistence length of surfactant monolayers and to estimate theoretically the positions of the neutral surfaces for different kinds of surfactants. The distance-eta-0 plays the role of unknown parameter and is used to fit the experimental data with the theory. The values of eta-0 vary for the considered surfactants in the range from 0.7 to 1.1 nm.