Long-Range Effects on Polymer Diffusion Induced by a Bounding Interface

We have measured the diffusion of deuterated polystyrene of molecular weight $90\times {10}^3$ in various matrices of hydrogenated polystyrene as a function of distance from an attractive interface, oxide-covered silicon. Surprisingly long-range effects are observed. Diffusion rates an order of magnitude slower than bulk persist up to ${10R}_g$ (radius of gyration) from the interface of either the diffusant or matrix polymers. The slowdown is independent of matrix molecular weight over a broad range. However, mixing of polymers within the matrix strongly influences the rates of diffusion.