Preparation And Characterization Of PMMA/SiO₂ Organic-Inorganic Composite Particles And Inorganic Hollow Spheres

In recent years, the strategy to fabricate organic/inorganic composite particles aroused the interest of materials scientists, because these particles combined the merits of organic materials and inorganic materials. Also, hollow spheres are becoming one of the focuses of new materials research, principally because such spheres display novel properties, such as low density, high specific surface areas, excellent stability and infiltration ability. In this study, SiO₂/PMMA composite particles with raspberry-like or core-shell morphologies were obtained via conventional emulsion polymerization. In addition, hollow titania spheres and hollow silica spheres containing nanosilica particles inside were prepared via a facile method. All the research contents and results are as follows:(1) By the aid of acid-base interaction between the auxiliary co-monomer 4-VP and the silica bearing OH group, the SiO₂/PMMA composite particles were prepared via conventional emulsion polymerization. In this method, no pretreatment of silica particles was needed.The morphologies of the resulted composite particles, e.g., multicore-shell, raspberry-like and conventional core-shell, could be controlled by modulating emulsifier content, monomer/silica ratio, silica size and monomer feed method. TEM, SEM, TGA and Zeta potential analysis were used to characterize the composite particles. Also, the possible formation mechanisms of the composite particles were discussed.(2) A facile route was employed to prepare hollow titania spheres using positively charged polystyrene particles as templates. In this approach, the titania shells formed and the polystyrene cores were dissolved subsequently even synchronously in the same medium, neither additional dissolution nor calcination process was needed to remove the polystyrene cores. TEM, SEM, FTIR, TGA and BET measurement were used to characterize the monodisperse hollow titania spheres. A possible formation mechanism of the hollow spheres was proposed.(3) Furthermore, this method employed to synthesize titania hollw spheres was used to prepare hollow silica spheres containing nanosilica cores as well. In this approach, positively charged SiO₂/ polystyrene core-shell composite particles were synthesized first, the silica shells from the sol-gel process of tetraethoxysilane coated on the surfaces of composite particles via electrostatic interaction, then the polystyrene was dissolved subsequently even synchronously in the same medium to form hollow silica spheres with small silica cores. TEM, SEM and FTIR measurements were used to characterize these composite spheres. Based on this study, some inorganic or organic compounds could be loaded into these hollow silica spheres.