Systematic synthesis of polyimide@inorganics core-shell microspheres via ion-exchange and interfacial reaction

• New route of preparing inorganic nanocrystal shell on polyimide core was proposed.
• The method relies on the ion-exchange and interfacial reaction.
• Precise control of size, structure and constituent of inorganic shell was achieved.
• A broad range of magnetic properties can be feasibly incorporated.
• Serve as a benchmark for preparing core-shell/organic-inorganic composite systems.

Uniform and stable core-shell microspheres composed of a polyimide (PI) core and thin metal/oxide/sulphide shells were prepared by an interfacial reaction of metal-ion-doped polymeric cores in reduction or in the air or sodium sulphide solutions, respectively. The silver shells on polyimide microspheres were prepared by the introduction of silver ions into ion-exchangeable surface-modified polyimide, and subsequently an in situ reduction of the silver ions in solution. Oxides shells such as SnO2, Co3O4, NiO, CuO or ZnO were prepared by thermally treating the ion-doped microspheres in air, while amorphous sulphides shells such as CuS, ZnS, CoS or Ag2S were prepared by an interfacial reaction of metal-ion-doped microspheres in its corresponding sodium sulphide solutions. The adhesion properties between the copper sulphide and PI substrates are demonstrated superior. This simple strategy is promising in the fabrication of a whole range of inorganic shells on polyimide microspheres, which may offer tailor-designed multi-functionalities based on the distinctive species of these inorganic shells.

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