| In this study, ultrasound was first introduced for preparing polymer nanomaterials, the poly(n-butyl acrylate) nanoparticle, poly(n-butyl acrylate)(PBA)/nanosilica composites, conductive polyaniline nanoparticle, polyaniline/nano TiO2 composite, polyaniline/nanoSiO2 composite were prepared through ultrasonic irradiation techniques. The main conclusions are as follows:(1) Ultrasonically initiated emulsion polymerization of n-butyl acrylate (BA) without any added initiator was conducted. PBA nanoparticle was succefully prepared. The factors affecting the induction period and conversion of BA monomer were investigated in detail. The induction period can be almost eliminated by enhancing the N2 purging rate. Increasing ultrasound intensity in the range of cavitation threshold and cavitation peak value, decreasing monomer concentration and increasing the temperature make the induction period shorter. Under optimized reaction conditions, the conversion of BA can reach 90% in 11 min at high N2 flow rate The viscosity average molecular weight of the obtained PBA reaches 5.24×106. The molecular weight of PBA varies with ultrasonic irradiation time, indicating that the ultrasonic induced emulsion polymerization is dynamic and quite complicated, polymerization of monomer as well as degradation of polymer occurs concomitantly. 1H-NMR, 13C-NMR and FT-IR analysis reveal that there are some branches and slight crosslinks, as well as carboxyl groups in PBA due to some special chemical reaction induced by ultrasonic irradiation. The particle size of PBA latex particles is in the range of 40-100 nm, as measured by TEM observation, suggesting that ultrasonic irradiation offers a new route to the preparation of mini- or micro- emulsionpolymerization. Moreover, ultrasonically initiated semi-continuous and continuous emulsion polymerizations were carried out. Both semi-continuous and continuous emulsion polymerization rate are slower than batch emulsion polymerization. A free radical polymerization mechanism for ultrasonically irradiated emulsion polymerization was proposed.(2) Ultrasonically irradiated encapsulating emulsion polymerization was first used to prepare polymer /inorganic nanoparticles composites. The behaviors of several inorganic nanoparticles (SiO2, Al2O3, TiO2) under ultrasonic irradiation, such as dispersion, crushing and activation, were studied. TEM, FTIR, spectrophotometry characterized the morphology, structure and dispersion stability of nanoparticles respectively. The results show that the inorganic nanoparticles in the aqueous solution can redisperse more effectively through ultrasonic irradiation than by conventional stirring, which was the basis for monomers to polymerize on the surface of nanoparticles. By selecting proper nanoparticles and monomers, the long-stable latexes were successfully prepared. TEM, FTIR, TG, XPS, spectrophotometry and element analysis confirmed that well-dispersed nanoparticles were encapsulated by formed polymer. The main affecting factors for encapsulation polymerization of BA, MMA, St and their copolymerization were investigated in detail. The results suggested that the pH value, the type of monomers, the type, concentration and surface properties of inorganic nanoparticles, the type and concentration of emulsifier have a great influence on the encapsulating emulsion polymerization and the obtained latex stability. If selecting cationic emulsifier (CTAB), low water soluble monomers (such as BA, St) and hydrophobic nano-silica, the inorganic nanoparticles would be encapsulated by polymers through ultrasonic irradiation successfully under alkalescent condition. The fundamental mechanism of ultrasonically initiated encapsulating emulsion polymerization to prepare polymer/inorganic nanoparticles composites were proposed.(3) Polyaniline (PANI) nanoparticles were prepared through ultrasonic assisted inverse microemulsion polymerization method. The size of polyanilinenanoparticles prepared in the colloidal dispersion is...
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