Polymer Diffusion in the Interphase Between Surface and Solution

Langmuir. 2018 Jun 19;34(24):7021-7027. doi: 10.1021/acs.langmuir.8b00660. Epub 2018 Jun 5.

Abstract

Total internal reflection fluorescence correlation spectroscopy (TIR-FCS) is applied to study the self-diffusion of poly(ethylene glycol) solutions in the presence of weakly attractive interfaces. Glass coverslips modified with aminopropyl- and propyl-terminated silanes are used to study the influence of solid surfaces on polymer diffusion. A model of three phases of polymer diffusion allows to describe the experimental fluorescence autocorrelation functions. Besides the two-dimensional diffusion of adsorbed polymer on the substrate and three-dimensional free diffusion in bulk solution, a third diffusion time scale is observed with intermediate diffusion times. This retarded three-dimensional diffusion in the solution is assigned to the long-range effects of solid surfaces on diffusional dynamics of polymers. The respective diffusion constants show Rouse scaling ( D ∼ N-1), indicating a screening of hydrodynamic interactions by the presence of the surface. Hence, the presented TIR-FCS method proves to be a valuable tool to investigate the effect of surfaces on polymer diffusion beyond the first adsorbed polymer layer on the 100 nm length scale.

Publication types

  • Research Support, Non-U.S. Gov't