Shaped silicas transcribed from aggregates of four-armed star polyethyleneimine with a benzene core

The formation of shaped silicas directed by a star poly(ethyleneimine) (sPEI4-200, with benzene core, four arms, and 200 repeated units per arm) was reported. The resulting silicas were characterized with scanning electronic microscope, optical/fluorescence microscope, and UV-vis and fluorescence spectrometers. We found that the silicas could be controlled into a rich variety of shapes and structures, including nanofiber-based bundles, flowers, films, or plates and continuous silica films, depending on the modulations of polymer concentrations and methanol and tetrakis(4-sulfonylphenyl) porphyrin (TSPP) addition. We further found that the silica directed by the star is remarkably star-specific in comparison with the linear counterpart. Star architecture enhances the parallel aggregation of unit silica fibers and also promotes the ability to form nanofibers. This aggregation enhancement was tentatively proposed to be intramolecular interaction of ethyleneimine segments in star structure associated with a specific conformation distribution of PEI arms tethered at a small benzene core. For silica formation, TSPP-modulation route facilely afforded the porphyrin-functionalized and shaped silicas that are potentially applicable in medical, photonic, electronic, and catalytic fields.