Fig. 1
From: Hybrid nanostructured particles via surfactant-free double miniemulsion polymerization
Transformation of a double miniemulsion to nanocapsules. a–c Fluorescence micrographs of primary water-in-styrene/PEOS emulsion, water-in-styrene/PEOS-in-water double emulsion, and resulting water@SiO2@polystyrene@SiO2 nanocapsules, respectively. The mass ratio of PEOS to styrene is 1:1, the inner water phase to the oil phase is 1:10, and the primary W/O emulsion to the outer water phase is 1:10. The pH value of the water phase is 7. Pink color represents the oil phase labeled with Nile red and green color shows the aqueous phase labeled with fluorescein sodium salt. Scale bars = 5 μm. d Chemical structure of polyethoxysiloxane (PEOS). e Field-emission scanning electron microscopy (FESEM) and f transmission electron microscopy (TEM) images of the water@SiO2@polystyrene@SiO2 nanocapsules. g TEM image of the particles shown in e and f after calcination in a muffle oven, where thin silica layers are pointed out by white arrows. Scale bars in the electron microscopy images are 200 nm. h Size distribution of the primary W/O emulsion and size evolution of the W/O/W double emulsion during polymerization measured by dynamic light scattering. PDI is polydispersity index. i Fourier-transform infrared spectra of PEOS, pure polystyrene, dried water@SiO2@polystyrene@SiO2 nanocapsules, and silica material obtained after calcination of the nanocapsules at 600 °C in air
