Transport properties of condensed monolayers

Abstract

In an earlier paper, monolayer permeability was derived on the basis of the fluctuations that occur in monolayer density at equilibrium. In this paper, the same model is used to derive the monolayer transport properties. First, expressions are developed for the probability and for the frequency of local expansions. These expressions are then used to derive the self-diffusion coefficient (D), the viscosity (η), and the thermal conductivity (κ) of a monolayer in terms of properties that are related to the surface isotherm. Whereas D has a reasonable magnitude, η is extremely small and many orders of magnitude lower than measured surface viscosities. The differences are discussed in terms of the monolayer model and the effect of the subphase. The utility of the model for processes involving natural membranes is also considered.