NEUTRON REFLECTIVITY AND SURFACE-TENSION MEASUREMENTS OF A DIBLOCK COPOLYMER MONOLAYER ON A SELECTIVE SOLVENT

We report measurements of the concentration profile of the submerged block of a diblock copolymer monolayer at the air surface of a selective solvent. The profile is found to contain a depletion layer near the surface (approximately 35 angstrom), followed by a parabolic (or similar) decay which tails off smoothly away from the surface. The dependencies of the maximum dimension (h*) of the profile on the surface density (sigma) and the molecular weight (M) of the submerged block are found to be weaker than those predicted in the limit of strong stretching, but are in reasonably good agreement with numerical SCF calculations of Whitmore, et al. A sharp rise in the surface pressure (measured simultaneous with the reflectivity) is observed for each sample at high surface densities which is not predicted by the existing mean-field or scaling theories.