Fabrication Of Hybrid Silica Hollow Spheres From Hyperbranched Polymer Unimolecular Micelles

During the past decades, hybrid silica hollow nano-sphere has attracted a lot of attention from both academic and industrial fields because of their lower density, larger specific surface area and internal cavity, higher chemical and thermal stability, etc. All these great properties make this kind of material very good candidates for applications in the following areas, such as filtration, catalysis, separation, controlled release, nano-medicine, etc. After years of efforts, hybrid silica hollow nano-sphere has already made a lot of progresses, such as obtaining a series of resultant silica spheres with uniform size, getting the nano-sphere with controlled size within a certain size range, building new special kinds of structures, and developing easier preparation methods, etc. However, there's still one tough challenge for the preparation of hybrid silica hollow nano-sphere with super small size, in particular for preparing those silica spheres with size below 50 nm. This may somehow restrict its applications in some nanotechnology fields.Hyperbranched polymers (HBP) are one kind of highly branched nano-molecules with three-dimensional structure. Especially, the amphiphilic hyperbranched polymer with one hydrophobic core and many hydrophilic arms can make the polymer survive stably in form of unimolecular micelles in the pure water or mixed solvent of water and some organic solvents. In this dissertation, we're going to use hydropobic polyester H40 to initiateε-caprolactone to prepare multi-arm star hyperbranched polymer (H40-star-PCL) with many poly(ε-caprolactone) (PCL) arms. Furthermore, the hydrophilic polyethylene glycol (PEG) was grafted on the end of H40-star-PCL to form the final amphiphilic hyperbranched polymer (H40-star-(PCL-b-PEG)) with H40-star-PCL as hydrophobic core and PEG as hydrophilic shell. Then, the hydrophobic tetraethyl orthosilicate (TEOS) was encapsulated into the hydrophobic core of hyperbranched polymer to form HBP/TEOS complexes. By optimizing the reaction condition, the hydrolysis of TEOS was controlled well and the silicon source grew into mineralization layer from the inside out gradually and finally to form a small-sized hybrid silica nano-sphere with HBP micelle core and silica shell.In the traditional template method of fabricating the hollow silica nano-sphere, the silicon source was got from the outside. On the contrary, in this dissertation, the silicon source TEOS was encapsulated into the hydrophobic core of unimolecular micelles and grew from the inside of HBP out to form small-sized hybrid silica nano-sphere. In a short sentence, we provide a new strategy for the preparation of a small-sized hybrid silica nano-sphere.