Homopolymer adsorption at the liquid-air interface by XEWIF

The adsorption of poly(dimethylsiloxane) to the in surface from solution in bromoheptane (good solvent) and bromocyclohexane (T θ =29 o C) has been studied. The sensitivity of the XEWIF technique to the first ∼40 A of the surface region allows the determination of important qualitative features of the absorbed concentration profiles. In a good solvent, the region of the profile nearest to the surface (∼40 A) is roughly independent of molecular weight in dilute solution. For near-θ conditions, the adsodrbed amount in dilute solution was found to be ∼4 times larger than in good solvent, with the profile decaying much more slowly with depth than in good solvent