Direct Measurement of Solvation Forces in Complex Microporous Media: A New Characterization Tool

We present a new beam bending (BB) technique for measuring solvation forces in complex microporous materials. The solvation forces are compressive and monotonically increasing with relative pressure. This is in stark contrast to Laplace−Kelvin theory (LKT) which predicts only tensile stresses. Applying a nonlocal density functional theory (DFT), the observed monotonic, compressive stresses are shown to arise from molecular sized pores with modest pore size polydispersity where the half-width of the distribution is 0.2−0.7 nm. Finally, the combined BB/DFT analysis provides a novel and much needed method for characterizing the morphology of microporous thin film materials to 0.1 nm resolution.