Phase transitions in thin smectic films at the air-water interface

Abstract

A Schiff’s base ferroelectric liquid-crystal P-hexyloxybenzylidene-p’-amino-2-chloro-α-propyle-cinnamate was spread on water to create a monomolecular film. Lateral compression led to several collapses at areas in the relation 1:1/2: 1) / 3 , etc. suggesting that smectic layers had been formed. The transitions from layers n to n+1 are considered phase transitions, the entropies of which were determined on the basis of experimentally observed lateral pressures as a function of the number of layers and temperature. The effect of the aqueous subphase and its contribution to the entropy is evaluated. The initial layer is found to be of lower symmetry than the upper layers. The lateral film pressure contains a strong dynamic component that is used to determine the viscosity for the transition as a function of temperature and the speed at which the film is compressed.