X-Ray Reflectivity Investigations of Fluorinated Amphiphilic Triblock Copolymers on Surfaces

The behaviour of amphiphilic block copolymers at a hydrophilic-hydrophobic interface has a great influence on their potential for pharmaceutical applications. Langmuir Blodgett (LB) films of two types of poly(perfluorohexyl ethyl methacrylate)-b-poly(ethylene oxide)-b-poly(perfluorohexyl ethyl methacrylate) obtained from the air-water interface at a surface pressure of 35 mN/m are investigated X-ray reflectivity (XR) measurements give a significant layer thickness of approximately 10 nm. This value is significantly smaller than the expected thickness of at least 15 nm which can be calculated from the transfer ratio and mean molecular area. Using atomic force microscopy (AFM), crystallisation of the sample with the typical finger structure, is observed From the height and surface covering of the fingers, the background height can be estimated to be in the range of 10 nm. The incorporation of copolymers in a lipid monolayer is observed by AFM on LB film and by XR on the Langmuir trough.