Small Molecule Diffusion in Polymer Ultra-Thin Films

Abstract

AbstractThe influence of film thickness and polymer molecular weight on the diffusion coefficient of water in poly(methyl methacrylate) thin films supported on gold coated surfaces has been studied using vapor sorption experiments via quartz crystal microbalance (QCM) methods. Diffusion coefficients for films ranging in thickness from approximately 1 μm to 50 nm were determined. It is observed that the diffusion coefficient of water in PMMA on weakly interacting substrates is a strong function of film thickness, and that the diffusion coefficient decreases drastically as film thickness is reduced below a critical thickness value. Furthermore, it is found that polymer molecular weight also appears to play an important role in determining the diffusion behavior of such polymer thin film systems.