Nano-scale mapping of mechanical and chemical surface properties of pigment coated surfaces by torsional harmonic atomic force microscopy

In this study, torsional harmonic atomic force microscopy (TH-AFM, HarmoniX mode) was applied for surface mapping of the mechanical properties of pigment-latex coated paper samples. In addition, topographic images and force maps of adhesive tip-sample interactions were captured concurrently. The spatial distribution of latex binder on the composite surface was distinguished with high resolution. The latex was found to dominate the surface chemistry of the composite coating, despite the fact that latex is a minor component in the coating color formulation. The latex resided as a thick layer between the pigments and as a thin layer on the individual pigments. In addition, the tip-sample thermodynamic work of adhesion of the composite materials on the coated surface was compared to the surface energy values obtained by contact angle measurements. A high tip-sample work of adhesion correlated to high surface energy.