Mixed Langmuir Films of 1-Heptadecanoic Acid and 1-Bromohexadecane

Abstract

Films of 1-heptadecanoic acid and 1-bromohexadecane have been studied by measuring the surface pressure-area (π-A) isotherms at 15°C during compression. Pure bromohexadecane on a pure water surface does not form an insoluble monolayer. The configuration of the mixed isotherms changes with composition. For many of the mixed film isotherms, the liquid portion of the curve is subdivided into more than one region, and the near vertical region disappears above 30 mol% of bromohexadecane. In this range the monolayer collapses prior to the formation of a condensed phase, suggesting that some of the bromohexadecane molecules have been squeezed out of the monolayer. On the basis of the partial molecular areas and the monolayer collapse pressures it can be concluded that films of this particular acid/alkyl bromide mixture can be made (and presumably successfully transferred to a suitable substrate by a Langmuir-Blodgett technique) provided that the mol fraction of bromohexadecane does not exceed 0.3.