Determination of the Concentration Profile at the Surface of d-PS/h-PS Blends Using High-Resolution Ion Scattering Techniques

Using the high-resolution ion profiling techniques of secondary ion mass spectrometry (SIMS) and time of flight forward recoil elastic scattering (TOF-FRES), we have measured the surface concentration profiles for a series of deuterated polystyrene (d-PS)/hydrogenated polystyrene (h-PS) blends as a function of deuterium volume fraction and annealing time. The data show that the profile is formed at a rate determined mostly by the bulk mutual diffusion coefficient. The form of the profile away from the surface (Z > 100 Å) is in agreement with predictions of current mean-field theories. On the other hand, in the near surface region (Z < 100 Å) a distinct flattening of the profile is observed, indicating that the short-ranged form of the interaction assumed in these theories may not be valid.