Size Distribution Of Nanoparticles Self-Assembly Encapsulation Emulsion

In recent years, more attentions have been focused on the method of preparing microcapsules with particles self-assembling on the interface of oil-water. Many researches are also carried out in the field of the adsorption of nanoparticles at oil/water interface and the emulsions stabilized by such particles (also called Pickering emulsions). However, the former work mainly concerned the morphologies and characters of emulsions, ignored the drop size distribution and monodisperse emulsion. Therefore, in this dissertation, we choose the Pickering emulsion stabilized by magnetic Fe₃O₄ nanoparticles as model, and discuss the effective factors of monodisperse emulsion systematically. The results are helpful for preparing monodisperse magnetic micro-capsules in the future.Using chemical coprecipitation method, the magnetic Fe₃O₄ nanoparticles were prepared. The morphology, crystal and size distribution of Fe₃O₄ were studied with TEM, FTIR and XRD technology. The TEM image of Fe₃O₄ and the size distribution chart analyzed from TEM image show that the diameter interval of Fe₃O₄ is 8-20nm, the average diameter is 14nm, and the size distribution is also well. The XRD spectrum of Fe₃O₄ shows that the outcome is pure. For preparing Pickering emulsion, we useα-Bromoisobutyric acid (BIBA) and sodium dodecyl sulfate (SDS) for surface modification of Fe₃O₄. The FTIR spectrum shows that BIBA and SDS can change the hydrophobic properties of Fe₃O₄ effectively.For studying the factors of dispersancy of emulsions, first of all, we set up a suspension polymerization experiment as a reference. We study the effect of agitation, concentration of dispersant and the temperature of water phase etc on preparing monodisperse polystyrene particles. The result indicates that: agitation and the concentration of dispersant are main factors to size distribution. The temperature of water phase also can affect the size distribution because its effect on the viscosity.Combined with the conclusion of the reference experiment, we study the effect of the amount of BIBA, Fe₃O₄, agitation, oil/water ratio, temperature of water phase, pH value and the concentration of electrolyte etc on the drop size distribution of Pickering emulsion systematically, and get an optimized condition for preparing monodisperse Pickering emulsion. We also prepare the composited Fe₃O₄ particles modified by BIBA and SDS, and make a primary research on the effect of the amount of SDS on the mean drop size and size distribution of emulsion. The result indicates that: the monodisperse Pickering emulsion can be prepared under the condition of oil/water ratio: 1:1 (150ml:150ml), agitation time: 10min, temperature: 25℃, Fe₃O₄: 2.32g, BIBA: 1.16g, pH=8-9, and the concentration of electrolyte (KCl): 0.02mol/L. The emulsion is stable and with an average drop size dV=60.43μm, dispersity CV=22.0%. The composited Fe₃O₄ particles modified by BIBA and SDS can make positive effect on the stability and drop size distribution of Pickering emulsion. When SDS/BIBA is 1/4, the average drop size and dispersity of emulsion are dV=38.04μm, CV=16.3% respectively, which is better than other situations.