Production of NiMn2O4 hollow spheres and CoFe₂O₄ bowl-like structures by using block copolymer stabilized polystyrene spheres as a hard template

The aim of this study is to highlight the use of polystyrene (PS) latexes stabilized with block copolymers as a hard template in the production of metal oxide hollow spheres. PS latexes produced by dispersion polymerization by stabilizing with tertiary amine methacrylate-based diblock copolymer were used as a hard template in the preparation of nickel manganese oxide (NiMn₂O₄) hollow spheres and cobalt iron oxide (CoFe₂O₄) bowl-like structures. Thanks to the diblock copolymer stabilizer with tertiary amine functional groups on the PS surface, precursor salts of CoFe₂O₄ and NiMn₂O₄ were first homogeneously deposited on the surface of PS latexes with a controlled precipitation technique. Then, metal oxide hollow spheres and bowl-like structures were produced by calcination. XRD results showed that CoFe₂O₄ and NiMn₂O₄ structures were successfully obtained after calcination. The thermogravimetric analysis results showed that the CoFe₂O₄ and NiMn₂O₄ contents of the hybrid PS spheres were in the range of 26.0-28.6 wt%. SEM images showed that the inorganic-polymer spheres fused with each other after calcination to form larger magnetic CoFe₂O₄ bowl-like structures. SEM images also indicated successful production of highly rough NiMn₂O₄ hollow spheres with nanosheets on the surface.