Dynamics of Spontaneous Spreading on Energetically Adjustable Surfaces in a Partial Wetting Regime

Using molecular-kinetic theory, the effects of the substrate surface energy on the time relaxation of the contact angle of squalane droplets are investigated. The studied surfaces are mixed Langmuir-Blodgett films composed of two kinds of molecules of equivalent length but with different end groups: n-tricosanoic and ω-tricosenoic acids. The two-dimensional miscibility of these chemical compounds over the complete range of relative concentration is discussed on the basis of various criteria. We show that the critical surface tension and the friction coefficient of the squalane molecules on these surfaces, calculated from the relaxation of the contact angle, are linear functions of the relative concentration of the ω-tricosenoic acid in the monolayers.