Theoretical and experimental study of the flow of condensed molecular monolayers on a Langmuir trough

Abstract

The induced flow of a condensed molecular monolayer on a rectangular through has been investigated both theoretically and experimentally. Two cases have been considered : (1) the induced flow caused by transfer along the trough of a monolayer between two barriers, (2) the flow caused by compressing a monolayer by a barrier at one end. It is assumed that the monolayer can be modelled as a Newtonian fluid and that interactions with the subphase are insignificant. The calculated flow profiles and streamlines are compared with the observed flow of octadecanoic acid and poly(butyl methacrylate) as typical monolayers. The results are found to be consistent with the theoretical model and show that some parts of the monolayer are sheared much more than others. This is a consequence of the use of sliding barriers to manipulate the film and is important in relation to studies of monolayers at high surface pressures, to LB film deposition and to phenomena associated with collapse of the monolayer.