Depth distribution of different solvents in a phase-separated block copolymer thin film

The structural change induced by the contact with different solvents was investigated for a diblock copolymer thin film, of polystyrene (PS) and poly(2-vinylpyridine) (P2VP), forming a lamellar structure by in-situ neutron reflectometry with a conventional cell for the measurement on solid/liquid interfaces. In the case of methanol, which is a selective solvent for P2VP, the structural change was induced by the penetration of methanol into the film, and the original lamellar structure was almost recovered by drying the film even after the solvent contact. On the other hand, when toluene was used as a selective solvent for PS, the block copolymer thin film was easily dissolved into toluene, and its original state was never recovered after the solvent contact. Further, water induced the structural change in the block copolymer thin film similarly to methanol, though it is a poor solvent common for PS and P2VP.