Study of mixed Langmuir and Langmuir–Blodgett films of dissimilar components by AFM and force spectroscopy

In this study the structure of mixed Langmuir–Blodgett (LB) monolayers has been investigated using atomic force microscopy, lateral force microscopy and force spectroscopy, as well as the characteristics of the Langmuir monolayers by surface pressure–area isotherms and Brewster angle microscopy. Mixed films were of dissimilar compounds, a fatty acid such as arachidic acid and a macrocyclic compound. The mixture forms separated phases, but some degree of partial miscibility occurs, with domains at the micro-scale that have different nanomechanical and nanotribological properties. LB films transferred at the same surface pressure show different characteristics depending on the composition. The higher domains correspond to arachidic acid and some of these domains show the presence of two phases, which have been identified as phases with discrete molecular tilting angles.