Structural diversity of multi-hollow microspheres via multiple Pickering emulsion co-stabilized by surfactant

This paper presented a facile approach to fabricate interconnected multi-hollow polymer microspheres by water-in-oil-in-water (W/O/W) multiple emulsions co-stabilized by SiO₂ and Span80. Two-step emulsification was employed to obtain W/O/W emulsion, followed by polymerizing the monomer into the skeleton of microspheres. The inner structure of microspheres was successfully regulated by adjusting the relative amount of SiO₂ to Span80. A large range of microspheres with different inner structures was obtained, including close-celled microspheres, interior hollowed microspheres, interconnected microspheres by single channel or multi-channels, and bicontinuous structure. A formation mechanism of microspheres with different inner structure was proposed and verified by the characteristic of released Ca²⁺ from inner aqueous phase to outer aqueous phase. These microspheres have advantages of high surface area, high porosity, and multi-hollow structure.