Crystallite structure formation at the collapse pressure of fatty acid Langmuirfilms

Abstract

We report isotherm and atomic force microscopy studies of collapsed Langmuirmonolayers of fatty acids. The Langmuir monolayers were overcompressed in the range7–40 °C and transferred onto mica after the sharp pressure drop when the collapse pressure wasreached. Collapsed material was observed by AFM, which revealed that the multilayers areindeed three-dimensional crystallites. We found that the shape of the crystallites dependson the collapse temperature, the phase from which the collapse occurs and/or the chainlength. However, at higher temperatures the collapsed films no longer show a welldefined crystallite formation, but rather a more heterogeneous melt-like pattern. Weassociated the crystallite formation with known bulk crystal phases of the fatty acids.