The tracer diffusion coefficients $D^{*}$ of polystyrene (PS) chains near PS melt-solid interfaces have been measured by secondary ion mass spectrometry. The $D^{*}$ for poly(2-vinylpyridine) (PVP) and oxide (SiO) covered silicon surfaces were smaller by, respectively, ∼3 and ∼${10}^2$ than for diffusion near the vacuum interface. $D^{*}$ scaled with degree of polymerization $N$ as $N^{-\propto }$, with ${\alpha }_{\mathrm{PVP}}=1.7\mathrm{}\left(1\right)\mathrm{}$ and ${\alpha }_{\mathrm{SiO}}=1.5\mathrm{}\left(1\right)\mathrm{}$. These results are in excellent agreement with reptation theory modified to account for increased friction due to surface-monomer contacts. The monomeric friction coefficients were found to be 98 ± 13 (PVP) and 5750 ± 450 (SiO) times greater than the bulk melt values.

• Received 14 July 1994

DOI:https://doi.org/10.1103/PhysRevLett.74.407