Fabrication and photoactivity of a tunable-void SiO2-TiO2 core-shell structure on modified SiO2 nanospheres by grafting an amphiphilic diblock copolymer using ARGET ATRPElectronic supplementary information (ESI) available: Additional FT-IR, TGA, TEM, FESEM, and HRTEM images of the hybrid microparticles. See DOI: 10.1039/c3sm52482e

SiO 2 -based composites have important applications in various technological fields. In this work, a tunable-void SiO 2 -TiO 2 core-shell structure was successfully prepared for the first time using SiO 2 -polymethyl methacrylate (PMMA)-polyoligo(ethylene glycol)methyl ether methacrylate (PO(EO) n MA) ( n = 2, 5, and 8). An amphiphilic copolymer was used as the template, and calcination was performed using tetrabutyl titanate (TBT) as the titanium source. SiO 2 -PMMA- b -PO(EO) n MA microspheres were first synthesized through activators regenerated by electron transfer-atom transfer radical polymerization. Methyl methacrylate and O(EO) n MA were grafted with different EO unit numbers onto the surface of the halogen functional group of SiO 2 . TBT was hydrolyzed along with the PO(EO) n MA chain through hydrogen bonding, and then the SiO 2 -TiO 2 core-shell structure was acquired through calcination to remove the polymer. Simultaneously, amorphous TiO 2 crystallized during calcination. A series of characterizations indicated that the amphiphilic block copolymer was grafted onto SiO 2 mesoparticle surfaces, the titania samples existed only in the anatase phase, and the prepared SiO 2 -TiO 2 had hierarchically nanoporous structures. The gradient hydrophilicity of the PMMA- b -PO(EO) n MA copolymer template facilitated the hydrolysis of TBT molecules along the PO(EO) n MA to PMMA segments, thereby tuning the space between the core and the shell. In addition, the space was about 6 nm when the EO number was 2, and the space was about 10 nm when the EO numbers were 5 and 8. The photocatalytic activities of the SiO 2 -TiO 2 materials were tested on the photodegradation of methyl orange. The fabrication of SiO 2 -PMMA-PO(EO) n MA hybrid microspheres can be easily done using ARGET ATRP. The space between the core and the shell can be adjusted by different EO units in an amphiphilic copolymer.