Enrichment depth profiles in polymer blends measured by forward recoil spectrometry

A novel time-of-flight detector system for He ⁺ forward recoil spectrometry which improves the depth resolution to better than 35 nm has been used to investigate the form of the surface enrichment profile in a protonated (normal) polystyrene (PS)/deuterated polystyrene (d-PS) blend. The volume fraction φ of d-PS depends on the depth z as φ(z)= φ_∞+(φ₁-φ_∞) exp(-z/), where φ₁ and φ_∞ are the surface and bulk volume fractions of d-PS, respectively, and is approximately the bulk correlation length, as predicted by theory.