Eur. Phys. J. E 6, 191-200 (2001)

Flow-controlled growth in Langmuir monolayers

R. Bruinsma¹, F. Rondelez² and A. Levine<sup>3

1</sup>  Physics Department, University of California, Los Angeles, CA, 90024, USA and Instituut Lorentz voor Theoretische Natuurkunde, Universiteit Leiden, Postbus 9506, 2300 Leiden, The Netherlands
²  Laboratoire de Physico-Chimie Curie, Institut Curie, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05, France
³  Department of Chemical Engineering, University of California, Santa Barbara, CA, 93106, USA

bruinsma@physics.ucla.edu

(Received 21 May 2000 and Received in final form 18 June 2001)

Abstract
We propose a hydrodynamic mechanism, based on the Marangoni flow, to describe growth instabilities of liquid-condensed islands in the supercooled liquid-expanded phase of two-dimensional Langmuir monolayers. This Marangoni instability is intrinsic to Langmuir monolayers and is not controlled by the expulsion of chemical impurities from the liquid-condensed phase. The hydrodynamic transport of the insoluble surfactants is shown to overwhelm passive diffusion and to provide a mechanism for fingering instabilities. The model can explain the observations by Brewster-angle microscopy of ramified liquid-condensed islands in monolayers that do not contain the fluorescent dye impurities, which are normally believed to be responsible for Langmuir-film growth instabilities.

PACS
05.70.Np - Interface and surface thermodynamics.
68.18.Jk - Phase transitions.
47.20.Dr - Surface-tension-driven instability.


© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2001