PLAWM trough

Figure 13.2 Langmuir and PLAWM trough with a monolayer indicated by amphiphilic molecules.

If the amphiphile is significantly soluble in the liquid, we cannot use a Langmuir trough any longer because amphiphiles would diffuse via the liquid phase to both sides of the barrier. We can use a PLAWM1 trough instead [577, 578], In the PLAWM trough a flexible membrane, which is fixed to the barrier, separates the two compartments. This membrane is easily movable, so that the barrier position is affected only by surface effects. 

Film Balance A shallow trough that is filled with a liquid on top of which is placed material that may form a monolayer. The surface area available can be adjusted by movable barriers, and any surface pressure thus created can be measured by means of a float. Also called Langmuir Film Balance, Langmuir Trough, and Pockels—Langmuir—Adam—Wilson—McBain Trough or PLAWM Trough. 

PLAWM Trough (Pockels—Langmuir—Adam—Wilson—McBain Trough)... 

PLAWM Trough. Pockels-Langmuir-Adam-Wilson-McBain trough. See Film Balance. 

Figure 5.3 Film balances a. Langmuir trough having a movable barrier and a Wilhelmy tensiometer to measure the spreading pressure, n, for water insoluble monolayers, b. PLAWM (Pockels, Langmuir, Adam, Wilson and McBain) trough used for partially water-soluble monolayers, where a flexible membrane, which is fixed to the barrier, separates the surfactant solution and pure water departments to prevent the passage of dissolved surfactant molecules into the pure water department beneath the barrier.

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