Concentration Profile of a Dissolved Polymer near the Air-Liquid Interface: X-Ray Fluorescence Study

Abstract

The x-ray fluorescence, at the near-total external reflection configuration, was employed to study the concentration profile of a dissolved polymer near the liquid-gas interface. The determined experimental concentration profile conformed with a hyperbolic cotangent squared dependence with a concentration excess ratio of about 100:1 of the surface relative to the bulk. This experiment presents the first direct measurement of that kind at the air-liquid interface and demonstrates the effectiveness of this new method to study nondestructively interface structures on the scale of tens to hundreds of angstroms.