DIHEDRAL ANGLE AT SOLID LIQUID-POLYMER INTERFACES DETERMINED BY ATOMIC-FORCE MICROSCOPY/

We describe a novel approach based on atomic force microscopy to deter mine the dihedral contact angle of a liquid polymer on top of a solid substrate. By cross-linking the polymer in an ion beam, the polymer su rface becomes amenable to AFM imaging. This sample preparation enables us to take topography scans of the polymer in a solid state. The cros s section of the contact area of a polymer drop and the substrate can then be utilized to determine the contact angle between polymer and su bstrate. Extremely low contact angles in the range 2-8 degrees are rep roducibly measured. Control measurements carried out with optical phas e modulated interference microscopy gave contact angles well comparabl e to the AFM results. We use our method in a study of polymer dewettin g on top of a network of itself.