Preparation And Modification Of Hollow Silica Microspheres

Mono-dispersed hollow SiO2 microspheres can be widely applied in different fields, including energy storage, catalysis, and biomedicine, due to its property such as monodispersity, high specific area, low density, and large inner space. The mesoporous structure of mono-dispersed hollow SiO2 microspheres makes it possible to not only load more drug but also release drug sustainedly and slowly. Therefore, many research efforts have focused on designing the hollow mesoporous silica microspheres with desired structures and particle sizes. This thesis adopts hard-template method to prepare mono-dispersed hollow SiO2 microspheres with different morphology, and the forming mechanism of different morphology is studied. The modification and grafting of mono-dispersed hollow SiO2 microspheres are also studied. Detailed contents in this thesis are shown as follows:1. We prepared two kinds of mono-dispersed polystyrene (PS) microspheres with different surface electrical property from the polymerization of styrene in water using different initiators. The PS microspheres prepared with potassium persulfate (KPS) as initiator (PS-a) have negative zeta potential in water, and those prepared with 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AIBA) as initiator (PS-c) have positive zeta potential in water. Then, we studied the morphology of hollow SiO2 microspheres prepared through hydrolysis and condensation of TEOS on the surface of the template microspheres. When the PS-a microspheres were used as the template, raspberry-like hollow silica microspheres were obtained. However, when PS-c template microspheres were used as the template, a smooth and dense silica layer will grow on the microsphere surface.2. We prepared the hollow mesoporous silica (HMS) microspheres with diameter of 320 nm using PS-c as templates and CTAB as porogen. We also studied the influence of ammonia, TEOS, and CTAB concentrations on the morphology, diameter, and shell thickness of HMS microspheres. The shell thickness of HMS microspheres increase with ammonia concentration, and then decrease with higher ammonia concentration. The shell thickness of HMS microspheres increase with TEOS concentration. But, the inference of CTAB concentration on the shell thickness was not obvious. We also prepared HMS-MPS and HMS-RAFT through modification of HMS microspheres with MPS and RAFT agents, respectively. The grafting degree of PDMAEMA on HMS-MPS and HMS-RAFT through initiator-induced, radiation-induced, and RAFT polymerization are 16.9%,14.7%, and 29.4%, respectively, and the specific area of products through initiator-induced, radiation-induced, and RAFT polymerization are 20.4 m2/g,20.1 m2/g, and 20.7 m2/g, respectively, which are all much lower than that of HMS microspheres (789.4 m2/g).3. We prepared PS-a@SiO2&PMO Janus particles through anisotropic nucleation and growth from PS-a@SiO2 seeds. After CTAB and PS-a were removed, we got acorn-shaped H-S-a&PMO Janus particles. The forming process of the acorn-shaped H-S-a&PMO Janus particles was also studied.