The Liquid-Liquid Langmuir Trough is for the suspension of monolayer films at the interface between two liquids, typically oils and water-based solutions. Surface pressure measurement of the oil-water interface during monolayer compression is achieved using a Wilhelmy plate in the conventional way.
The lower liquid subphase (the more dense medium) is filled to the upper level of a PTFE insert that sits in the bottom of the PTFE trough. The compression barriers sweep along the upper surface of this PTFE insert, compressing the monolayer at the liquid-liquid interface.
The total depth of the Liquid-Liquid Langmuir Trough is 8mm. The height of the PTFE insert is 4mm. The upper liquid subphase (the less dense medium) is added on to the denser subphase surface and filled to the upper level of the trough face. As the compression barriers are shorter than the width of the trough opening, but longer than the width of the PTFE insert opening, the upper subphase is free to flow around the compression barriers while a monolayer is confined to the liquid-liquid interface.
With the PTFE insert in place, the trough has a lower subphase area of 40x5cm and a maximum monolayer containment area of 185cm2.
This trough can also be used to study the air-water interface in the same way as a conventional Langmuir Trough by removing the PTFE insert and filling to the upper level of the trough face. In this mode, the subphase area is 45x7cm and the maximum monolayer containment area is 295cm2. An additional pair of lengthened compression barriers are provided that are capable of spanning across the width of the trough opening for use in this single-subphase mode.
