Surface enrichment in an isotopic polymer blend

Forward-recoil spectrometry reveals that the surface of a blend of deuterated polystyrene (d-PS) and protonated polystyrene (PS) is enriched with d-PS relative to the bulk; the surface excess of d-PS increases almost linearly with the bulk volume fraction φ of d-PS at 184°C. The results may be interpreted quantitatively with mean-field theory, and yield a form of the bare surface energy of the blend consistent with the surface enrichment being driven by a surface-energy difference between d-PS and hydrogenated polystyrene (h-PS) of isotopic origin.