Fabrication of Cobalt Oxide‐Block Copolymer Nanostructured Hybrid Films via a Mixed Solvent System

ABSTRACT The synthesized cobalt oxide (CoO) nanosheets embedded within a polymer matrix hold significant potential for applications in sensors, organic electronics, catalysis, organic photovoltaics, and energy storage devices. Using a facile and efficient preparation technique, we combine an organometallic cobalt(II) precursor, a polystyrene‐ block ‐polymethyl methacrylate (PS‐ b ‐PMMA) diblock copolymer (DBC), and organic solvents to ensure complete dissolution of all components without inducing precipitation or micro‐phase separation in the liquid phase. Through a straightforward thermal annealing process, the cobalt salt within the DBC thin films undergoes decomposition, resulting in the formation of CoO nanosheets with a uniform and dense distribution pattern matching the morphology of the DBC. Fourier transform infrared spectroscopy (FTIR) confirms selective phase separation of the cobalt salt within the DBC, while x‐ray photoelectron spectroscopy (XPS) indicates the conversion of the salt into CoO. The morphology of the CoO/DBC hybrid films is characterized using atomic force microscopy (AFM), scanning electron microscopy (SEM), and x‐ray scattering techniques. This study demonstrates a simple and effective route to prepare a well‐defined arrangement of metal oxide clusters, achieving a highly confined particle self‐assembly process compared to alternative solution‐based methods.