Preparation Of Nanocapsules And Magnetic Composite Hollow Microspheres

In this thesis, firstly, we prepared the polystyrene nanocapsules by radiation induced miniemulsion polymerization and studied the effect of factors on the final morphology from the both thermodynamic and kinetic theory; then we prepared the magnetite/polystyrene composite spheres and hollow spheres and studied the some influence of factors. The main results obtained in this dissertation are described as follows:1. Preparation of polymeric nanocapsules by radiation induced miniemulsion polymerization(1) Polystyrene (PSt) nanocapsules with liquid core were prepared by ⁶⁰Coγ-ray radiation induced miniemulsion polymerization, in which N-vinyl pyrrolidone (NVP) was used as polar monomer. The characterization of polymer was carried out by ¹H NMR. It was verified that during the polymerization, graft copolymerization between poly (pyrrolidone) (PVP) and PSt has taken place instead of random copolymerization. The interfacial tension between polymer and water was reduced because of the grafting reaction occurring, which was helpful to form of nanocapsules. The influence of the ratio of St to NVP, the type and amount of the surfactant and the monomer/dodocane ratio on the particle morphology was studied by TEM. Finally, the releasing process of the synthesized nanoparticles is monitored by UV-visible measurement.(2) Polystyrene nanocapsules were parepared by the miniemulsion polymerization stabilized by Y-like polymerizable emulsifier AOA. The result showed when oil/water=2:10, St/HD=1, 2.2 wt% AOA to the continueous phase, PH=8, the nanocapsules with good structure could be obtained. Increasement of PH and decrease of the concentration of AOA and dose rate were disadvantaged for the formation of nanocapsules.2. Interface-initiated emulsion polymerization: synthesis of hollow sphere with a hole in the shell. The polystyrene hollow spheres with a hole in the shell can be successfully prepared by interface-initiated emulsion polymerization in the presence of isooctane. The redox initiator, CHPO-FeSO4 initiated the polymerization of styrene at the droplet interface. Because the phase separation between the PSt and isooctane occurred during the polymerization, and isooctane was partially encapsulated by PSt, the hollow spheres with a hole in the shell were formed. The results indicated that at the low St/isooctane ratio, the amount of isooctane has influence on the hollow size of hollow polymer spheres. Higher St/isooctane ratio and the addition of DVB were disadvantaged for the formation of the hollow structure.3. Preparation of magnetite/polystyrene composite particles via inverse emulsion polymerization(1)Super-paramagnetic magnetite/polystyrene composite particles were prepared by inverse emulsion polymerization with water-based magnetic ferro-fluid as dispersing phase, and organic solvent and styrene (St) as continuous phase. And the mechanism of the nucleation was discussed. The influence of factors, such as the monomer content, the amount of the ferro-fluid and the different continuous phase on the morphology of the magnetite/polystyrene composite particles was studied. The final products were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric analysis (TGA). Magnetic hysteresis loop measurements revealed that the composite particles were super-paramagnetic. (2) Preparation of hollow magnetite/polystyrene composite microsphere via inverse emulsiuon polymerization induced byγ-ray. Super-paramagnetic Fe₃O₄/PSt composite microspheres were prepared by radiation-interfacial-initiated inverse emulsion. The final products were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS). The influence of the content of AOA and addition of silicon on the final morphology was studied. The result showed that the addition of silicon at the low concentration of AOA (3ï¼…) and the high concentration of AOA were advantanged for the formation of hollow magnetite/polystyrene composite microsphere.