Reptation dynamics of a polymer melt near an attractive solid interface

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 ∼102 than for diffusion near the vacuum interface. D* scaled with degree of polymerization N as N-∝, with αPVP=1.7(1) and αSiO=1.5(1). 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.