Multihollow nanocomposite microspheres with tunable pore structures by templating Pickering double emulsions

Micrometer-sized dual nanocomposite polymer microspheres with tunable pore structures were fabricated using a simple and straightforward method based on Pickering double emulsions. First, a primary water-in-styrene (oil) emulsion (w1/o) was prepared using the hydrophobic silica nanoparticles as a particulate emulsifier without any molecular surfactants. Then, a water-in-styrene-in-water (w1/o/w2) Pickering emulsion was produced by the emulsification of the primary w1/o emulsion into water using Fe3O4 nanoparticles as external emulsifier. The big styrene droplets containing small water droplets were polymerized after the formation of the double emulsions. Nanocomposite polystyrene microspheres with a multihollow structure were obtained and their morphological structures were studied by scanning electron microscopy (SEM). The pore structure of the microspheres could be tuned by the volume ratio of the internal water phase to the medium oil phase (w1:o) of the primary emulsions. With increasing w1:o from 1:8 to 4:1, the amount of the pores in one microsphere increased gradually and the pore structures changed from close to interconnected. The resulting multihollow microspheres had a responsive ability to magnetic stimulus due to the existence of Fe3O4 nanoparticles. This kind of multihollow hybrid polymer microspheres is expected to have a wide potential application in materials science and biotechnology.