The poly(acrylic acid) was used as dispersant to prepare aqueous TiO2/poly(acrylic acid) suspensions. The poly(acrylic acid) was adsorbed on the surface of the TiO2 particles. The zeta potential of the TiO2 particles in TiO2/poly(acrylic acid) suspensions was higher than that of the TiO2 particles in TiO2 suspensions, and the zeta potential of the TiO2 particles increased with increasing poly(acrylic acid) content. At the same shear rate, the viscosity of TiO2/poly(acrylic acid) suspensions was lower than that of TiO2 suspensions, and the liquidity was improved. The dispersion of TiO2 particles in TiO2/poly(acrylic acid) suspensions was improved compared with that of TiO2 particles in TiO2 suspensions. 相似文献
Most magnetic composite materials have a serious sedimentation problem because of their large density. When the nanomaterials are combined with magnetic materials, the density would become larger. In this article, polystyrene (PS) beads were used as core to synthesize raspberry-like PS-Fe3O4@TiO2 particles (PFTPs) by a facile method, which could float on the water. The loaded Fe3O4@TiO2 particles were characterized by X-ray diffraction (XRD), which could confirm the anatase phase TiO2 coated on Fe3O4 nano-particles. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) confirmed the presence of acrylic acid in reaction media could effectively tune the morphology of resulting composite particles between “core-shell” and “raspberry-like”. The data of Vibrating sample magnetometer (VSM) indicated the change in saturation magnetization before and after TiO2 coated, the introduction of PS could further influence the saturation magnetization of Fe3O4. Lastly, we proved the sedimentation stability of PFTPs via capturing the photographs of them in water and oil. 相似文献
In a mixed solvent of water and ethanol, polystyrene/titanium dioxide (PSt/TiO2) composite particles of core-shell structure were prepared by hydrolysis of tetrabutyl titanate in the presence of cationic PSt particles or anionic PSt particles surface-treated using γ-aminopropyl triethoxysilane. Hollow TiO2 particles were obtained through calcination of the PSt/TiO2 core-shell particles to burn off the PSt core or through dissolution of the core by tetrahydrofuran (THF). An alternative process constituted of preheating the PSt/TiO2 particles at 200°C to allow partial crystallization followed by calcination or PSt dissolution by THF. The outcome TiO2 particles thus prepared were examined by TEM, and hollow TiO2 particles were observed. The crystalline phase structure and phase transformation were characterized, which revealed that preheating before the removal of the PSt core was useful to achieve the desired hollow TiO2 particles, and the calcination process was beneficial to the formation of anatase and rutile structures. The tests of TiO2 particles as catalyst in the photodegradation of Rhodamine B demonstrated that a much higher catalytic activity was observed with the TiO2 hollow particles prepared through calcination combined with preheating. 相似文献
Titanium dioxide (TiO2) sol (TS) or TiO2 nanoparticles with chitosan shell were encapsulated to enhance their sun protection abilities. Nanocapsules loaded with TiO2 were evaluated for their ultraviolet (UV) absorption and UV protection rate. The effect of eicosapentaenoic acid (EPA) incorporation into the nanocapsules was examined in relation to UV absorption. The particle size of TiO2 crystallites in TS was below 30 nm, which was considerably smaller than that of a commercial TiO2 (P25 TiO2) particles. In the encapsulation of TiO2 with chitosan, the loading efficiencies of TS were higher than those of P25 TiO2. The sizes of the nanocapsules loaded with TiO2 particles ranged from 30 to 80 nm. The absorption range of irradiation wavelength was enlarged by the incorporation of EPA into the nanocapsules. The TS-loaded nanocapsules exhibited a high UV protection rate of up to 95% to both UV-A and UV-B. 相似文献
In this study, acrylic-based nanocomposites containing different contents of multi-walled carbon nanotubes (MWCNTs) and metal oxide nanoparticles (i.e., TiO2, CuO and Fe2O3) were fabricated by solvent mixing method. The thermal conductivity of these samples was evaluated. The results indicated that the thermal conductivity of all fabricated samples was significantly improved even at small loading of MWCNTs. It was found that the thermal conductivity was enhanced by increase in MWCNTs content up to 5 wt%. Similarly, the metal oxide nanoparticles caused up to 75 % increment in thermal conductivity at 1.5 wt% of their loading in acrylic film. Contrary to expectations, the thermal conductivity of acrylic film was more increased by nanometal oxides (i.e., TiO2, CuO and Fe2O3) than MWCNTs. The effect of hybridizing of nanometal oxide particles (1.5 wt%) and MWCNTs (1.5 wt%) on thermal conduction was investigated as well. It was found that hybridizing improved thermal conductivities by about 85, 94 and 97 % for Fe2O3, TiO2 and CuO, respectively. Finally, the effects of TiO2 pigment and CaCO3 extender on the thermal conductivity of acrylic polymer and nano-TiO2 acrylic composites were studied. It was found that TiO2 could increase considerably thermal conduction of its acrylic films and acrylic nanocomposites. 相似文献
Nano-sized Pd/polystyrene composite nanoparticles were prepared via surfactant-free emulsion polymerization. The as-prepared composite particles were used as a catalyst for Suzuki reaction, and they showed excellent catalytic properties in the conversion and recyclability. First, polystyrene (PS) latex particles bearing carboxyl groups on the surfaces were synthesized via one-stage surfactant-free emulsion polymerization employing acrylic acid as the functional monomer. Thus, made the PS particles negatively charged and could attract positively charged Pd2+ ions. By adding PdCl2 solution to this functional polystyrene emulsion, Pd2+ ions were attached to the surfaces and reduced to zero valent particles by the reducing agent, NaBH4. Nano-sized Pd/PS composite particles could be synthesized via this facile method. The amount of the functional monomers, the Pd2+ content and the amount of the initiator played important roles to the final morphologies of the composite particles. The resulting composite microspheres were observed by TEM. Furthermore, catalytic properties of the as-prepared Pd/PS composite particles were studied via Suzuki reaction, and the results were characterized by FTIR and 1H-NMR. The Pd/PS composite particles showed excellent conversion and could be recycled easily for reuse. After each round of Suzuki reaction, the Pd/PS composite particles could be separated just by filtration, the conversion still remained as high as 70.2?%, even when used 5 times. 相似文献
Well-defined polymer-TiO2 nanocomposites of core–shell structure were prepared by two-steps, surface-initiated atom transfer radical polymerization (ATRP) of styrene and in situ chemical oxidative polymerization of aniline monomers from the surfaces of the TiO2 nanoparticles. The methods used include the following: initially, the ATRP initiator was covalently attached to the surface of TiO2 nanoparticles by esterification of 2-bromo-2-methyl propionic acid with hydroxyl group. The metal-catalyzed radical polymerization of styrene with modified TiO2 nanoparticles was performed using a copper catalyst system to give the TiO2-based core hybrids linking PSt segments (TiO2-PSt hybrids). Next, the TiO2-PSt reacted with HNO3/H2SO4 to produce a nitro group containing polystyrene to form TiO2-PSt-NO2, and obtained TiO2-PSt-NO2 was treated with hydrochloric acid/SnCl2, and converted to an amine group containing polystyrene (TiO2–PSt-NH2). Finally, surface oxidative graft copolymerization of aniline, using the –NH2 moieties of TiO2/PSt-NH2 as the anchoring sites. Characterization of these well-defined nanocomposites included FTIR, thermogravimetric analysis, transmission electron microscopy, and X-ray diffraction. 相似文献
The aim of this study was to evaluate the acute lung toxicity in rats of intratracheally instilled TiO2 particles that have been substantially encapsulated with pyrogenically deposited, amorphous silica. Groups of rats were intratracheally
instilled either with doses of 1 or 5 mg/kg of hydrophilic Pigment A TiO2 particles or doses of 1 or 5 mg/kg of the following control or particle-types: 1) R-100 TiO2 particles (hydrophilic in nature); 2) quartz particles, 3) carbonyl iron particles. Phosphate-buffered saline (PBS) instilled
rats served as additional controls. Following exposures, the lungs of PBS and particle-exposed rats were evaluated for bronchoalveolar
lavage (BAL) fluid inflammatory markers, cell proliferation, and by histopathology at post-instillation time points of 24
hrs, 1 week, 1 month and 3 months. 相似文献
This work reports a simple and efficient preparation method of an inverse‐opal‐like macroporous polytetrafluoroethylene (IO‐PTFE) film with a reusable matrix. At first, the pH‐responsive poly(acrylic acid) (PAA) is grafted on the PTFE latex particles induced by γ‐ray radiation. The stability of PAA grafted PTFE latex particles (PTFE‐g‐PAA) in water decreases in acid aqueous solution. As a result, PTFE‐g‐PAA particles can coprecipitate with monodispersed polystyrene (PS) microspheres from the acidic aqueous dispersion to form a composite particulate film. After the composite particulate film is etched with toluene to remove PS microspheres, a self‐stand inverse‐opal‐like macroporous PTFE film can be successfully obtained. The macroporous PTFE film can be applied as the microreactor to synthesize uniform TiO2 particles. The separation of TiO2 microparticles and the recycle of PTFE‐g‐PAA particles can be simultaneously achieved simply in water by means of ultrasonification. The prepared TiO2 microparticles also show good photocatalytic performance. This work opens a new thought to prepare special macroporous polymeric materials, and expands the microsynthesis of inorganic or organic microparticles by taking advantage of polymeric macroporous materials.
Encapsulation of inorganic nanoparticles by polymers is one of the interesting research topics that lead to the synthesis of nanocomposites. These nanocomposite materials comprise the properties of both organic polymer and inorganic nanoparticles. Here, hybrid latex particles with core–shell nanostructure were prepared via semi-batch emulsion polymerization. Copolymers of (methyl methacrylate-butyl acrylate) and (dimethylaminoethyl methacrylate-butyl acrylate-acrylic acid) were formed as the inner and outer layers, respectively on the surface of modified TiO2 nanoparticles as the core. In order to create compatibility between inorganic and polymeric phases, modification of TiO2 nanoparticles was performed with glycidyl methacrylate with an optimized procedure for the first time and then emulsion polymerization was carried out. The products of each step were fully characterized. The results of dynamic light scattering, TEM and SEM analyses proved the formation of encapsulated hybrid latex particles. DLS and SEM data revealed that the sizes of nanocomposite particles vary between 85 and 120 nm for 0–5 wt% of the modified TiO2 nanoparticles. Physico-mechanical properties of the obtained nanocomposite films were studied by DMTA. It was found that using only 3 wt% of modified TiO2 improved those properties of resulting films remarkably. 相似文献
Novel, environmentally friendly waterborne coatings were obtained from the filmification of nanostructured latex particles reinforced with inorganic nanotubes. The latex used to form the coatings consists of core-shell particles with a shell functionalized with different amounts of acrylic acid (AA). This external polymer layer was doped, in some cases, with TiO2 nanotubes at three different concentrations: 100, 500 and 1000 ppm. The composite particles were synthesized in two steps by semi-continuous emulsion polymerization at 75°C. A series of films was prepared by employing core-shell particles with different sizes, core cross-linking and shell functionalization. The coatings obtained were characterized by infrared spectroscopy (FTIR), tapping mode atomic force microscopy (TM-AFM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetrical analysis (TGA). Drying rates and tests were also performed to further evaluate these films. It was observed that the addition of small amounts of TiO2 nanotubes contributes to improve the application properties, mainly adhesion to metallic substrates and water impermeability. The resistance to thermal degradation was also strongly increased, as showed by the DSC and TGA analyses. 相似文献