Structural Evolution During Repeated Spray Deposition of FeCl₃‐Doped Poly(Styrene)‐b‐Poly(4‐Vinyl Pyridine) Layers

Abstract Nanostructured hematite (α‐Fe₂O₃) films exhibit significant potential for energy, environmental, and medical applications. In the present work, a large‐scale spray coating deposition method, scanning electron microscopy, and in situ grazing‐incidence small‐angle X‐ray scattering are combined to investigate the structure formation mechanism of pure poly(styrene)‐b‐poly(4‐vinyl pyridine) (PS‐b‐P4VP) and hybrid PS‐b‐P4VP/FeCl₃ films during and after spray deposition. Under the film deposition conditions specified in this experiment, a layered pure PS‐b‐P4VP film, a sponge‐like hybrid PS‐b‐P4VP/FeCl₃ film, and a porous α‐Fe₂O₃ film are obtained upon completion of the deposition. The morphological differences between the investigated pure PS‐b‐P4VP and hybrid PS‐b‐P4VP/FeCl₃ films result from the interplay among the complexation between FeCl₃ and P4VP segments, the crystallization of the P4VP segment, and the surface diffusion of the FeCl₃ species. The findings of this work can offer both experimental and theoretical guidance for designing spray‐deposited block copolymer and hybrid films.