Transition from a complex to a simple two dimensional liquid: Isotherm and Brewster angle microscopy studies

Surface pressure versus Specific Molecular Area (Π-A) Isotherms for Langmuir Monolayers of stearic acid (StA), and stearic acid containing 10% and 50% (by mass) of dodecanethiol-capped Au nanoparticles (StAu10 and StAu50, respectively), have been recorded. The isotherms show a decrease in the magnitude of the slopes in both the 'liquid' L2 and L2. phases and the 'solid' S phase, as well as a decrease in the differences between slopes of all the adjacent phases, indicating a change from a complex to a simpler two dimensional liquid, progressively from StA to StAu10 to StAu50. Brewster Angle Microscopy (BAM) images show, for StA, formation of a continuous twodimensional body while, for StAu50, formation of aligned nanoparticle clusters, with compression.