Dynamics of layer-by-layer thinning of free-standing smectic films

A dynamic model has been proposed for describing the extrusion of a single layer of a liquid-crystal (LC) material into a meniscus from an N-layer circular free-standing smectic film (FSSF). In the framework of this model, the main mechanism responsible for the process of the thinning (extrusion) of the LC material from the $N$-layer FSSF is based on the appearance of a spatial pressure gradient directed along the radius of the circular FSSF. This gradient is formed due to the difference in the disjoining pressures on both sides of the front separating the $N$- and $(N–1)$-layer domains of the smectic film. The proposed model allows taking into account the influence of the meniscus on dynamic characteristics, such as the time required for the complete extrusion of a single layer from the $N$-layer FSSF and the velocity of propagation of the front separating the $N$- and $(N–1)$-layer domains in the process of the thinning of the smectic film formed by molecules of 5-$n$-alkyl-2-(4-$n$-(perfluoroalkyl-methyleneoxy))pentyl.