Supercritical Fluid On Polymer Microspheres And Inorganic Hollow Microspheres Preparation

In recent years, supercritical carbon dioxide (SCCO₂) has been explored for use in material science owing to its special physical, chemical, nontoxic and inexpensive advantages. SCCO₂ can dissolve into polymer and enhance the mobility of chains, which can alter the structure and properties. Inorganic hollow colloid microspheres has been prepared with assistance of special infiltration and mass transferability of SCCO₂. The obtained inorganic hollow colloid microspheres attracted more and more attentions due to their low density, high thermal and mechanical stability, which have many potential applications in a range of areas including catalysis, controlled delivery, and biological imaging.In chapter two, we synthesized submicron monodispersed polymer microspheres by using emulsifier-free emulsion polymerization. Ordered microsphere array were treated in SCCO₂. The sorption of CO₂ into polymer enhance chain mobility and reduce the glass transition temperature (Tg) of polymer, which induce the microsphere coalesce at relatively lower temperature than in ambient condition.In chapter three, we prepared micron polymer microspheres by using dispersion polymerization method. Treating these microspheres with SCCO₂, these microspheres were welded together. After ultrasonic treatment, the welded microspheres were separated and submicron sized pits were engraved on the surfaces of microspheres. The microspheres transformed from isotropy to anisotropy successfully. The coalescence degree of the polymer microspheres can be tuned by changing the temperature, pressure and treatment time of SCCO₂, which can affect the final morphology of the micro particles.In chapter four, base on data of anterior two chapters. We selected some appropriate SCCO₂ conditions which can keep the polymer microspheres from distortion. The precursors (Tetraethyl orthosilicate TEOS) were carried into the solid polymer templates to form TEOS/polymer composites with the assistance of SCCO₂. After the sol-gel procedure, the SiO₂/polymer organic-inorganic composites were obtained. Hollow SiO₂ microspheres can be obtained by calcining the organic-inorganic composites at high temperature.In summary, this paper has discussed the transformation of polymer microspheres after treatment in SCCO₂ and investigated a new pathway to change the property of the polymer. In addition, we have proposed a new method for the preparation of inorganic hollow microspheres with assistance of SCCO₂.