Pickering suspension polymerization was used to prepare magnetic polymer microspheres that have polymer cores enveloped by shells of magnetic nanoparticles. Styrene was emulsified in an aqueous dispersion of Fe3O4 nanoparticles using a high shear. The resultant Pickering oil-in-water (o/w) emulsion stabilized solely by magnetic nanoparticles was easily polymerized at 70 °C without stirring. Fe3O4 nanoparticles act as effective stabilizers during polymerization and as building blocks for creating the organic–inorganic hybrid nanocomposite after polymerization. The fabricated magnetic nanocomposites were characterized by FTIR, XRD, TGA, DSC, GPC, XPS and SEM. The structures of the polymer core and the nanoparticle shell were analyzed. We investigated the effects on the products of the weight of Fe3O4 nanoparticles used to stabilize the original Pickering emulsions. Pickering suspension polymerization provides a new route for the synthesis of a variety of hybrid nanocomposite microspheres with supracolloidal structures. 相似文献
Developing bio-friendly and degradable Pickering emulsifiers as surfactants to replace traditional surfactants with bio-toxicity is imperative in the food, coating, cosmetics, and pharmaceutical industries. Nanocellulose and chitin can be used directly as an emulsifier to prepare Pickering o/w emulsions. As the concentration of nanoparticles increases, the stability of the emulsion also increases, and an overly large nanoparticle aspect ratio is not conducive to the stabilization of the emulsion. In comparison, nanocellulose-prepared Pickering emulsion has improved stability. Of these, nanocellulose prepared by DES with a molar ratio of 3:1 to LA:CC has been shown to have the best stability when used to equilibrate the oil/water mass ratio of 2/8. The Zeta potential is −38.4 mV, and the size of the droplets is the most uniform. With a mean droplet diameter of 770 nm. This study had certain research significance and reference value for the development of bio-friendly surfactants. 相似文献
In this article, a facile method for fabrication of core–shell nanocomposite microspheres with polystyrene (PS) as the core and halloysite nanotubes (HNTs) as the shell via Pickering suspension polymerization was introduced. Stable Pickering emulsions of styrene in water were prepared using HNTs without any modification as a particulate emulsifier. The size of the Pickering emulsions varied from 195.7 to 26.7?μm with the water phase volume fraction increasing from 33.3 to 90.9?%. The resulting Pickering emulsions with the water phase volume fraction of above 66.7?% were easily polymerized in situ at 70?°C without stirring. HNTs played an important role during polymerization and effectively acted as building blocks for creating organic–inorganic nanocomposite microspheres after polymerization. The sizes of PS/HNTs microspheres were roughly in accord with that of the corresponding emulsion droplets before polymerization. The effect of the water phase volume fraction on the stability of Pickering emulsions and the morphologies of nanocomposite microspheres was investigated by optical microscopy, confocal laser scanning microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and so on. 相似文献
We studied the effects of emulsifiers on the entrapment yields of a hydrophilic material, calcein, in lipid vesicles formed using the multiple emulsion method. The primary emulsion (W1/O) was prepared via sonication while the secondary emulsification that produced the W1/O/W2 multiple emulsions was achieved using the microchannel (MC) emulsification technique. The emulsifiers used in the continuous (W2) phase were Tween® 80, Pluronic® F68, and bovine serum albumin (BSA). Lipid vesicles formed via solvent evaporation of the multiple emulsion droplets had an average diameter of about 180 nm, similar to the size of the water droplets in the primary W1/O emulsions. The entrapment yields of calcein increased with decreasing concentrations of Tween® 80 but decreased with decreasing concentrations of Pluronic® F68 and BSA. The effects of type and concentration of emulsifier were considered in relation to three possible mechanisms: (i) destabilization/solubilization of lipid bilayers by emulsifiers, (ii) reversed-micellar transport of W1 contents from internal to external water phases through the O phase, and (iii) release of inner water (W1) contents into the continuous (W2) phase via the instability of W1/O/W2 and leakage of W1 contents. Using the food grade emulsifier Tween® 80 at a low concentration of about 0.1 or 0.05 wt%, calcein as a model hydrophilic material could be efficiently entrapped (ca. 80%) in homogenously dispersed lipid vesicles. 相似文献
Polymerization using Pickering emulsion droplets as reaction vessels is being developed to become a powerful tool for fabrication of hybrid polymer particles with supracolloidal structures. In this paper, two kinds of thermo-sensitive hybrid poly(N-isopropylacrylamide) (PNIPAm) microcapsules with supracolloidal structures were successfully prepared from suspension polymerization stabilized by SiO2 nanoparticles based on inverse Pickering emulsion droplets. SiO2 nanoparticles could self-assemble at liquid-liquid interfaces to form stable water-in-oil inverse Pickering emulsion. NIPAm monomers dissolving in suspended aqueous droplets were subsequently polymerized at different temperatures. The hollow microcapsules with SiO2/PNIPAm nanocomposite shells were obtained when the reaction temperature was above the lower critical solution temperature (LCST) of PNIPAm. While the core-shell microcapsules with SiO2 nanoparticles' shells and PNIPAm gel cores were produced when the polymerization was conducted at the temperature lower than LCST using UV light radiation. The supracolloidal structures with different cores could be tuned by simply changing reaction temperature, which was confirmed by confocal laser scanning microscopy and scanning electron microscopy. The interesting properties of both microcapsules were their ability of reversibly swelling during drying/wetting cycles and responsive to temperature stimulus. Such functional microcapsules may find applications in double control release system due to the presence of the supracolloidal structures and thermo-sensitivity. 相似文献
Influences of process parameters were investigated on the efficiency of encapsulation of bovine serum albumin (BSA) in poly(dl-lactic-co-glycolic acid) (PLGA) nanoparticles produced by w1/o/w2 (water-in-oil-in-water) double emulsion-solvent evaporation method. According to a 5-factorial 3-level Box-Behnken type experimental design aqueous solution of BSA was emulsified in an immiscible organic phase composed of dichloromethane and various quantities of dissolved PLGA to get water-in-oil (w1/o) emulsion. This latter was then dispersed in a second aqueous phase (w2) containing poly-vinyl-alcohol (PVA) surfactant as an emulsifier/stabilising agent. PLGA nanoparticles with encapsulated BSA were obtained by evaporating the dichloromethane from the w1/o droplets. Encapsulation efficiency was determined as the weight ratio of BSA remained in the PLGA nanoparticles relative to the total weight of BSA used in the process. By statistical evaluation of the experimental results an equation was proposed to predict the encapsulation efficiency as a function of five process variables. Two optimization procedures were carried out to increase the efficiency of encapsulation, with and without constraints referring to the required mean particle size. Correlation was found between the latter and the achievable maximal encapsulation efficiency under optimal process conditions. 相似文献
A continuous process for methacrolein production was constructed by filling w/o Pickering emulsions in a column reactor. Ionic liquid (IL-[HDEA]Ac) with secondary amine was designed to catalyze propionaldehyde condensation with formaldehyde through the Mannich reaction. Emulsion droplets encapsulated with IL aqueous solution were stabilized with modified SiO2 nanoparticles and dispersed in cyclohexane, which could be observed as numerous reactors. The properties of SiO2 stabilizer, such as wettability, surface groups, and the effect on interfacial tension were investigated. The characteristics of emulsion influenced by stabilizer properties and content were systematically studied. The droplet size, IL concentration and liquid hourly space velocity were optimized. The droplets were evaluated at 0.5 hr−1 for 150 hr without IL leakage and obvious activity decreasing, indicating the excellent stability of the emulsion system. The continuous process showed a 1.25-fold enhancement in catalysis efficiency and less equipment compared to batch process. 相似文献
Summary: A method is presented that can produce ordered macroporous alginate membranes and microspheres with a relatively narrow pore size distribution as compared to other existing porous alginate matrix generating procedures. The calcium alginate membranes and microspheres obtained were multiporous, and the pore size could readily be adjusted in the range of 1 to 10 µm by selecting appropriate initial emulsion parameters. A preliminary set of experiments was used to determine a range of conditions suitable for the formation of stable O/W emulsions consinsting of the alginate solution, liquid paraffin and surfactants. The obtained emulsions were characterized by size distribution measurements and optical microscopy. The emulsions were used to form alginate membranes and microspheres with diameters of 150–500 µm. Subsequent work was performed to remove liquid paraffin droplets, the dispersed phase of the emulsion which acted as template in the pore‐generating process, from the final alginate membranes and microspheres. The states of templates in hydrogels and the effect of template removal on the calcium alginate structures were thoroughly investigated.
Porous alginate membranes prepared via emulsion templating method. 相似文献
Gold nanoparticle/graphene oxide hybrids (AuNP/GO) were easily fabricated by a redox reaction between GO and chloroauric acid without using any additional reductant and then used to stabilize Pickering emulsions. Factors affecting the properties of the emulsions were studied, including the HAuCl4/GO mass ratio used to prepare the AuNP/GO, the oil/water ratio, the AuNP/GO concentration, the pH value, and the type and concentration of electrolytes. The emulsions were more stable when stabilized by AuNP/GO made from HAuCl4/GO mass ratios of 0.375–0.5. High pH values and AuNP/GO concentrations that were too high or too low were unfavorable to the stability of the Pickering emulsions. Adding electrolytes to the systems improved the stability of the Pickering emulsions owing to the reduction of repulsive interactions between AuNP/GO sheets. The AuNP/GO stabilized Pickering emulsions were used to prepare AuNP/GO supported polystyrene (PS) microspheres (AuNP/GO@PS) by polymerizing the Pickering emulsion. The catalytic performance of AuNP/GO@PS for the reduction of 4-nitrophenol was then studied. 相似文献
We here propose a simple, facile, and effective method to prepare submicron mullite hollow spheres templated from Pickering emulsions. Dual-phase sol consisted of boehmite and silica nanoparticles decorated by pentanoate ion could assemble at water/oil interface irreversibly to form photosensitive Pickering emulsions. The droplets of emulsions could be separated by dilution and formed by photopolymerization to gain hybrid microspheres, which could completely transform to mullite hollow microspheres via binder removal and sintering. It is found that the prepared hollow microspheres possess intact morphology, favorable sphericity, large cavity volume, and bulk density of 0.356 g/cm3. Importantly, the average diameter of mullite hollow spheres obtained via this method could be as low as 0.33–2.31 μm. This steady method is efficient and suitable for various types of inorganic particles, providing an innovative perspective for preparing fine hollow spheres applicable for filtration, drug loading as well as energy storage areas. 相似文献
In this work, we describe a novel and simple method for fabricating biocompatible microcapsules. Chitosan colloidal nanoparticle-coated micrometer-sized poly(lactic-co-glycolic acid) (PLGA) microcapsules were fabricated via a combined system of “Pickering-type” emulsion route and solvent volatilization method in the absence of any molecular surfactants. Stable oil-in-water emulsions were prepared using chitosan colloidal nanoparticles as a particulate emulsifier and a dichloromethane (CH2Cl2) solution of PLGA as an oil phase. Moreover, this stable emulsion present a good pH-responsive characteristic. The uncross-linked chitosan nanoparticles coated PLGA microcapsules were fabricated by the evaporation of CH2Cl2 from the emulsion, and the cross-linked chitosan nanoparticles coated PLGA microcapsules were prepared by cross-linking with glutaraldehyde and evaporation of CH2Cl2. The two types of microcapsules were characterized in terms of size, morphology using scanning electronic microscope (SEM), optical microscope, and so on. These observations confirm the robust nature of these cross-linked microcapsules. Moreover, a possible mechanism for the formation of these microcapsules was proposed. The combined system of Pickering emulsion and solvent volatilization opens up a new route to fabricate a variety of microcapsules. 相似文献
A series of porous polymers with different pore volumes, pore sizes, and crosslinking densities were synthesized by high internal phase emulsion (HIPE) polymerization. The crosslinked polymerized HIPEs (polyHIPEs) were formed by the copolymerization of 4-vinylbenzyl chloride and divinylbenzene using water droplets in conventional or Pickering HIPEs as the templates. These porous materials were further modified by quaternization and ion exchange to introduce quaternary ammonium hydroxide groups. The resulting polyHIPEs were utilized as sorbents for reversible CO2 capture from air using the humidity swing. The effect of pore structure on the CO2 adsorption and desorption processes was studied. The polyHIPEs containing large pores and interconnected porous structures showed improved swing sizes and faster adsorption/desorption kinetics of CO2 compared to a commercial Excellion membrane with similar functional groups. 相似文献