Ion inclusion into Langmuir–Blodgett films studied on a quartz crystal microbalance

Abstract

The potential of a simple quartz crystal microbalance (QCM) system for the study of ion inclusion into Langmuir–Blodgett (LB) films is demonstrated for cadmium docosanoate multilayers over a range of pH values which cover the range of unbound acid films to the high pH salt films. The reproducibility of the deposition process, the number of ions bound per fatty acid molecule and the inclusion of water into the film are measured as a function of pH and compared with values from X-ray reflection measurements. The Microscopic drying process and its relevance to film repreoducibility are also investigated. There is a slight, significant change in the areal density of the fatty acid component as acid films are converted to fully bound ionic soap films, in addition to the well documented change in the unit-cell c-axis.