Determination of the Tilt Angle of Langmuir Monolayers with Brewster Angle Autocorrelation Spectroscopy and Quantitative Image Analysis in Brewster Angle Microscopy: A Comparison between Two Different Methods

Abstract

We have developed a method to determine the tilt angle of the aliphatic molecule chains of Langmuir monolayers on the water surface by combination of Brewster angle microscopy (BAM) and autocorrelation technique (Brewster angle autocorrelation spectroscopy). In this paper measurements of the surface pressure dependent tilt angle of stearic acid and arachidic acid monolayers on water will be presented. We compare our technique and the results with another previously presented method of quantitative image analysis in BAM. The comparison with X-ray diffraction data show that Brewster angle autocorrelation spectroscopy is an efficient tool for measuring the tilt angle in Langmuir monolayers with high accuracy.