Different dimensional silica materials prepared using shaped block copolymer nanoobjects as catalytic templates

Abstract

A general approach to fabricate a series of silica nanoobjects with sheet-like, tubular and hollow spherical shapes was reported. These silica nanoobjects were prepared by using water-dispersed diblock copolymer nanoobjects with glassy polystyrene cores and densely grafted poly(2-(dimethylamino)ethylmethacrylate) (PDMAEMA) shells as templates as well as catalysts. A sol–gel reaction of tetramethoxysilane (TMOS) was subsequently induced by PDMAEMA shells of shaped nanoobjects in water dispersions at near-neutral pH and under ambient conditions, and thus the shaped polymer@silica hybrids with a high silica content (around 70 wt% silica in hybrids) were obtained. Then silica nanoobjects of three different dimensions were further prepared by calcination at 650 °C to remove the organic components. The spherical and cylindrical silicas have a hollow structure. Formation of diblock copolymers, polymer nanoobjects, polymer@silica hybrids, and silica nanoobjects was characterized by ¹H NMR spectroscopy, size exclusion chromatography (SEC), small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), solid state ²⁹Si CPMAS NMR analysis, N₂ adsorption–desorption measurements, and Fourier-transform infrared spectroscopy (FT-IR). This methodology could be a general approach to fabricate various inorganic nanoparticles with different geometric shapes.