Transient processes at the deposition of charged Langmuir monolayers

An electrokinetic mechanism is proposed to explain the slow meniscus relaxation that is observed in experiments of the deposition of charged Langmuir monolayers on a solid substrate using the LB technique. The major element of the proposed mechanism amounts to the formation the ion concentration and electric potential profiles in the subphase close to the three-phase contact line during the monolayer transfer. A mathematical model is developed to describe the transition processes which occur in the subphase when the imposed speed of substrate changes with time transiently. The calculations on the basis of the proposed model predict meniscus relaxation times of the same order of magnitude as those observed in experiments. The obtained results are important for analyzing meniscus oscillations which lead to formation of striped patterns within the deposited LB films.