Thermal desorption of Langmuir-Blodgett layers

Abstract

The feasibility of using a quartz-crystal microbalance (QCM) of novel design to study the small changes in mass, produced by thermal desorption of Langmuir-Blodgett (LB) layers has been investigated. Layers of stearic acid and dipalmitoyl phosphatidyl choline with thicknesses ranging from one to twelve monolayers were deposited directly onto the quartz crystal, heated in vacuum, and the consequent mass loss recorded. Some mass change attributable to loss of water was observed for both materials. Kinetics of LB mass loss indicate a second-order process the temperature dependence of which reveals, for both molecules, two distinguishable binding energies. The QCM technique is shown to be capable of accurately measuring mass loss from multi-layer LB films, and, with some refinement, will yield useful information on desorption kinetics and binding energies of LB layers.