Unstable topography of biphasic surfactant monolayers

¹ The James Franck Institute, The University of Chicago - Chicago, IL 60637, USA
² Department of Physics, The University of Chicago - Chicago, IL 60637, USA
³ Department of Chemistry and Institute for Biophysical Dynamics The University of Chicago, Chicago, IL 60637, USA

Corresponding author: diamant@control.uchicago.edu

Received: 25 May 2000
Accepted: 4 September 2000

Abstract

We study the conformation of a heterogeneous surfactant monolayer at a fluid-fluid interface, near a boundary between two lateral regions of differing elastic properties. The monolayer attains a conformation of shallow, steep “mesas” with a height difference of up to 10 nm. If the monolayer is progressively compressed (e.g., in a Langmuir trough), the profile develops overhangs and finally becomes unstable at a surface tension of about , where is the difference in spontaneous curvature and K a bending stiffness. We discuss the relevance of this instability to recently observed folding behavior in lung surfactant monolayers, and to the absence of domain structures in films separating oil and water in emulsions.