Fabrication of SiO2 hollow microsphere with urchin-like structure based on template from directed assembly of block copolymer

We report here a novel strategy for fabrication of SiO2 hollow microspheres with urchin-like structure based on templates from directed assembly of block copolymer, poly(2-cinnamoyloxyethyl acrylate)-block-poly(acrylic acid-co-styrene) (PCEA-b-P(AA-co-Sty)). The structures of template from directed assembly of copolymers as well as that of as-obtained hollow SiO2 microspheres were observed by a combination technique of optical microscope, scanning electron microscope, and transmission electron microscopy. It is shown that the hollow microspheres consist of aligned SiO2 "spines" radially growing from the core which are induced a favorable growth by the structures of the template from directed assembly of PCEA-b-P(AA-co-Sty). The "spine" density of the hollow SiO2 sphere can be tuned by controlling the structure of the copolymer with different hydrolysis degree of poly(tert-butyl-acrylate) to PAA, and the ultimate size of the resultant SiO2 hollow sphere can be adjusted by solvent and temperature in the sol-gel process, etc.