Hollow mesoporous silica with a hierarchical shell from in situ synergistic soft–hard double templates

Traditional methods for the construction of hollow particles with a hierarchical shell mainly rely on complicated chemical routes and removal of the templates. Herein, hollow mesoporous silica particles with a sphere-on-sphere (SOS) structure were successfully synthesized via a one-pot method using a novel "in situ synergistic soft-hard double template" strategy, that is, styrene (St) droplets as a soft template and in situ polymerized PS nano-domains as a hard template. The pre-hydrolysate derived from the silica precursor methyltriethoxysilane could anchor on the surface of the St droplets due to its amphiphilicity and then continue hydrolysis-condensation to form the mesoporous silica shell (MSS). Subsequently, MSS was used as a nanoreactor, and some of the in situ polymerized PS chains in the nanoreactor migrated to the outer surface of MSS due to the action of strong capillary force in the mesoporous channels, while some of the siloxane oligomers migrated to the surface due to their apparent interfacial activity, resulting in the hierarchical appearance of SOS. Furthermore, other intriguing hollow silica particles with a hollow sphere-on-sphere (HOS) structure were obtained by calcining the obtained SOS particles. The application of the as-prepared SOS and HOS particles showed their potential in the superhydrophobicity and detoxification fields, respectively.