Preparation Of Titania Hollow Spheres By Template/Sol-Gel Method

In this paper, micron-sized polyacrylamide (PAM) spheres have been firstly prepared through the dispersion polymerization of acrylamide. Monodispersed positively charged PAM spheres were prepared by dispersion polymerization when PVP/AM=60% using azodiisobutyramidinedihydrochloride (AIBA) as initiator and without the addition of methacrylatoethyltrimethylammoniumchloride (DMC). These PAM spheres exhibited regular shape and narrow dispersity. The size of over 70% PAM spheres were between 400-500nm and the value of polydispersity index (PDI) was 1.15. Then, based on the former experiments, the coating reaction is done by hydrolyzing tetraisopropoxide (TTIP) when the concentration of water and PVP are 0.8mol/L and 0.5wt% under mild stirring. Negatively charged titania sol were captured by positively PAM spheres via electrostatic interaction. Both SEM and TEM indicated PAM/TiO2 hybrid spheres were prepared.The rigidity of polyacrylonitrile (PAN) is better than PAM. So we selected PAN as the template. Firstly, monodispersed PAN particles were produced through the dispersion polymerization of acrylonitrile. These PAN particles exhibited regular shape and narrow dispersity. The size of over 80% PAN spheres were between 400-700nm and the value of polydispersity index (PDI) was 1.07. The average particle size of PAN particles became larger with the increase of initiator concentration, the decrease of stabilizer concentration and the speed of stirring; at the same time, the average size of PAN particles first became larger and then decreased with the increase of monomer concentration and mass ratio of ethanol/water. TTIP was then added into one group with the best morphology when the concentration of water and PVP are 0.8mol/L and 1.0wt% under vigorous stirring. TEM showed little titania sol could be absorbed. The crystallinity of the PAN chains in the particles was confirmed by XRD. So PAN particles with perfect round morphology could not be obtained. One or two other kinds of monomers could be added to destroy the crystalline of PAN and obtain the critical diameter of microspheres when crystallinity does not affect the perfect round morphology of template spheres. So this work has provided relevalant theory and experiment research for future work.