In this paper, we have successfully fabricated the colloidal crystals of monodispersed polystyrene latex. Styrene was polymerized in degassed water at 75 ℃, using potassium persulfate as an initiator. The surfactant ...In this paper, we have successfully fabricated the colloidal crystals of monodispersed polystyrene latex. Styrene was polymerized in degassed water at 75 ℃, using potassium persulfate as an initiator. The surfactant was sodium dodecyl sulfate(SDS). Firstly, the monodispersed polystyrene latex with an average diameter of some nanometers was synthesized via emulsion polymerization, then these small latex particles were used to act as seeds for further growth. The size of polystyrene latex was controlled between 50 nm and 400 nm via diversifying the condition of polymerization. The resulted emulsion solution could accumulate slowly to form three dimensional ordered structure, which was induced by capillary as the solvent evaporating at room temperature. The opal is close packed face center cubic(f.c.c) lattice of polystyrene latex. Defects such as vacancies, dislocations or grain boundaries could be obviously observed from the SEM images. Reflectance spectra showed the red shift of specular reflectivity peak for the polystyrene colloidal crystal as the size of polystyrene latex increasing. It was demonstrated that the reflectance is intrinsic property of these colloidal crystals. This provides ideal model for the research and application of photonic crystals and form useful template for growth of various ordered macroporous materials.展开更多
Shear thickening fluids （STFs） based on additives with different concentrations and molecular chain lengths were investigated. STF samples were prepared with silica and additive dispersed in polyethylene glycol （PE...Shear thickening fluids （STFs） based on additives with different concentrations and molecular chain lengths were investigated. STF samples were prepared with silica and additive dispersed in polyethylene glycol （PEG） 400, where three types of additives with different molecular chain lengths of PEG4000, PEG6000, and PEG10000 were used. For PEG10000, different concentrations, including 0, 1%, 3%, and 5%, were selected to study the influences of additive concentrations. Rheological properties of the samples were measured with a rheometer. The results show that the shear thickening effect was significantly enhanced with the increase of the concentration and the molecular chain length of additives. The mechanism of enhancement was quantitatively explained with the formation of large particles clusters.展开更多
文摘In this paper, we have successfully fabricated the colloidal crystals of monodispersed polystyrene latex. Styrene was polymerized in degassed water at 75 ℃, using potassium persulfate as an initiator. The surfactant was sodium dodecyl sulfate(SDS). Firstly, the monodispersed polystyrene latex with an average diameter of some nanometers was synthesized via emulsion polymerization, then these small latex particles were used to act as seeds for further growth. The size of polystyrene latex was controlled between 50 nm and 400 nm via diversifying the condition of polymerization. The resulted emulsion solution could accumulate slowly to form three dimensional ordered structure, which was induced by capillary as the solvent evaporating at room temperature. The opal is close packed face center cubic(f.c.c) lattice of polystyrene latex. Defects such as vacancies, dislocations or grain boundaries could be obviously observed from the SEM images. Reflectance spectra showed the red shift of specular reflectivity peak for the polystyrene colloidal crystal as the size of polystyrene latex increasing. It was demonstrated that the reflectance is intrinsic property of these colloidal crystals. This provides ideal model for the research and application of photonic crystals and form useful template for growth of various ordered macroporous materials.
文摘Shear thickening fluids （STFs） based on additives with different concentrations and molecular chain lengths were investigated. STF samples were prepared with silica and additive dispersed in polyethylene glycol （PEG） 400, where three types of additives with different molecular chain lengths of PEG4000, PEG6000, and PEG10000 were used. For PEG10000, different concentrations, including 0, 1%, 3%, and 5%, were selected to study the influences of additive concentrations. Rheological properties of the samples were measured with a rheometer. The results show that the shear thickening effect was significantly enhanced with the increase of the concentration and the molecular chain length of additives. The mechanism of enhancement was quantitatively explained with the formation of large particles clusters.
