Novel and feasible method for synthesis of monodispersed hollow silicon dioxide submicrospheres

This study presents a simple approach to the preparation of hollow silica spheres via template-sacrificial techniques. The hard poly(styrene) (PS) template was prepared by soap-free emulsion polymerization in the boiling state for a specified period, followed by introduction of silane into the reaction system to generate the core–shell PS/silicon dioxide (SiO2) spheres without the use of structure-directing agents or surface modification. The SiO2 shell was constructed by co-hydrolysis/condensation of mixed silane containing various weight ratios of tetraethyl orthosilicate (TEOS) and triethoxymethylsilane. The degree of compatibility between PS and SiO2 was shown to be affected by the composition of the silane mixture, and increasing the proportion of TEOS in the silane mix enhanced the mechanical robustness of the SiO2 shell. Based on the residual weight percentage from thermogravimetric analysis, the portion of SiO2 in the PS/SiO2 spheres prepared using various compositions of silane was about 10 wt%. Furthermore, hollow SiO2 spheres were obtained by calcination of the PS/SiO2 spheres prepared using an appropriate formulation of silane at 400°C. Scanning electron microscopy analysis indicated that the size of the hollow spheres was about 200 nm, and the spheres displayed a high degree of monodispersity. Observation of certain cavities on the surface of the spheres also demonstrated the hollow structure of the SiO2 spheres.