Controlling sol–gel polymerization to create bowl-shaped polysilsesquioxane particles with a kippah structure

Bowl-shaped particles in sub-micrometer scale represent an interesting platform for many potential applications. However, controlled fabrication of this special structure based on polymers still remains a big challenge. In the present study, a controllable sol–gel polymerization procedure was developed to precisely prepare bowl-shaped polysilsesquioxane particles. The morphology of particles can be fine-tuned by judiciously adjusting the amount of two organoalkoxysilane precursors. We explored the formation mechanism of bowl-shaped polysilsesquioxane particles with a kippah structure. The flexibility of the shell and osmotic pressure in combination with centrifugal force should be the key factors to the formation of a bowl-shaped structure.