The distinct polymeric nanocapsule hybrid‐structures consisting of LCs in the core and PMMA or polystyrene in the corona domain were prepared by one‐step miniemulsion polymerization. Nematic LCs (4′‐pentyl‐4‐biphenylcarbonitrile and 4′‐heptyloxy‐4‐biphenylcarbonitrile) were especially adopted as hydrophobes that can suppress Ostwald ripening and had an important role to stabilize the miniemulsion droplets and control the size distributions of the latexes. The polymeric nanocapsule structures with narrow size distributions were confirmed by TEM and DLS measurements.
An isopropyl myristate (IPM) biocompatible oil and an IPM solution of dodecanethiol‐capped Ag nanoparticles (NPs, 4.5 nm) were used as hydrophobes to suppress the Ostwald ripening of monomer/hydrophobe miniemulsified droplets in a surfactant‐stabilized water phase. The formation of non‐IPM‐encapsulated nanospheres (48 nm) and IPM‐encapsulated nanocapsules (90 nm) were precisely controlled by using a water‐soluble and an oil‐soluble initiator, respectively, in the presence of a pure IPM as a hydrophobe in miniemulsion polymerization. Well‐defined PS nanospheres, on which surfaces were coated with Ag NPs (Ag/PS nanospheres, 65 nm), and nanocapsules encapsulating both NPs and IPM liquid phase (Ag‐IPM/PS nanocapsules, 115 nm) were made by replacing the hydrophobe from pure IPM with Ag/IPM solution. These nanostructures were characterized by transmission and scanning electron microscopes.
Monodisperse poly(D ,L ‐lactide) (PDLLA) microspheres have been prepared by dispersion polymerization of D ,L ‐lactide with a synthetic polymeric stabilizer. The polymerization is carried out in xylene/heptane (1:2, v/v) at 368 K for 3 h with poly[(dodecyl methacrylate)‐co‐(2‐hydroxyethyl methacrylate)] (P(DMA‐co‐HEMA)). P(DMA‐co‐HEMA) has hydroxy groups as an initiation group for pseudoanionic dispersion polymerization. The particle diameter and the coefficient of variation concerning the diameter distribution of the obtained PDLLA microspheres are 3.9 µm and 4.3%, respectively. In addition, from the results of dynamic light scattering measurements, it is found that P(DMA‐co‐HEMA) and the PDLLA‐grafted copolymer form a micellar structure in solution.
The semi real-time observations of oil-in-water emulsification process in a Kenics static mixer were performed using a novel in situ visualization system. The homogenization processes and emulsion characteristics were analyzed using images taken periodically in fixed time intervals during the emulsification process. Morphological evolution of droplets was monitored and the mechanism of droplet formation was studied, both experimentally and theoretically. A wide range of dispersed phase concentration as well as surfactant concentration were used in the experiments and their impacts on emulsion characteristics were determined. Different droplet formation mechanisms occurred during the experimental results are presented. The relationship between droplet sizes, flow rate, surfactant concentration, and other impact factors was visually shown, and their role in controlling the emulsification process was revealed. The minimum droplet size obtained from the dispersed phase in emulsions was shown to be perfectly monitored and controlled by this technique. 相似文献
Inorganic silica nanoparticles were encapsulated with an epoxy resin to give waterborne nanocomposite dispersions, using the phase‐inversion emulsification technique. Sub‐micron‐sized waterborne particles with narrow size distribution were prepared such. Microscopy results indicate that all the silica nanoparticles are encapsulated within the composites and uniformly dispersed therein. Curing of the nanocomposite dispersions proceeded in a controlled manner. 相似文献
In this work, formations of water-in-diesel fuel nanoemulsions using water/mixed nonionic surfactant/diesel fuel system has been studied. The high-energy emulsification method was used to form three emulsions using different water contents: 5, 10, and 14% (v/v) namely; E1, E2, and E3, respectively. These nanoemulsions were stabilized with emulsifiers having different hydrophilic lipophilic balance (HLB), namely, Span 80 (HLB = 4.3), Emarol 85 (HLB = 11), and their mixture (SE) with HLB = 10. The effect of water on the droplet size formation has been investigated. The interfacial tension and thermodynamic properties of the individual and emulsifiers blends have been studied. The interfacial tension (γ) measurements at 30°C were used to determine the critical micelle concentration (CMC) and surface active properties of these emulsifiers. The water droplet sizes were measured by dynamic light scattering (DLS). From the obtained data, it was found that mean sizes between 19.3 and 39 nm were obtained depending on the water content and concentration of blend emulsifiers (SE). Also, the results show that the interfacial tension (γ) gives minimum value (10.85 mN/m) for SE comparing with individual emulsifier (17.13 and 12.77 mN/m) for Span 80 and Emarol 85, respectively. The visual inspection by transmission electron microscopy showed that the obtained results support the data obtained by dynamic light scattering. 相似文献
Polyamide‐6 (PA6) submicron‐sized spheres are prepared by two steps: (1) anionic ring‐opening polymerization of ε‐caprolactam in the presence of poly(ethylene glycol)‐block‐poly‐(propylene glycol)‐block‐poly(ethylene glycol)(PEG‐b‐PPG‐b‐PEG) and (2) separation of PA6 spheres by dissolving PEG‐b‐PPG‐b‐PEG from the prepared blends. The PA6 microspheres obtained are regular spherical, with diameter ranging from 200 nm to 2 μm and narrow size distribution, as confirmed by scanning electron microscopy. By comparison with PA6/PS and PA6/PEG systems, it is denominated that the PEG blocks in PEG‐b‐PPG‐b‐PEG can effectively reduce the surface tension of PA6 droplets and further decrease the diameter of the PA6 microspheres. The PPG block in PEG‐b‐PPG‐b‐PEG can prevent the PA6 droplets coalescing with each other, and isolated spherical particles can be obtained finally. The phase inversion of the PA6/PEG‐b‐PPG‐b‐PEG blends occurs at very low PEG‐b‐PPG‐b‐PEG content; the PEG‐b‐PPG‐b‐PEG phase can be removed by water easily. The whole experiment can be finished in a short time (approximately in half an hour) without using any organic solvents; it is an efficient strategy for the preparation of submicron‐sized PA6 microspheres.
The organic nano-TiO2 was synthesized in reverse (W/O) microemulsion, using tetrabutyl titanate (TBOT) as precursor and γ-methacryloxypropyl trimethoxy silane (KH-570) as modifier. After phase inversion from W/O microemulsion to oil-in-water (O/W) emulsion, nano-TiO2/poly(methyl methacrylate) hybrid latex was prepared via in-situ polymerization based on the O/W emulsion containing organic nano-TiO2. Fourier transform infrared spectroscopy (FTIR) indicated that KH-570 was successfully grafted onto the surface of TiO2 particles. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) demonstrated that the average diameter of nano-TiO2 was about 10 nm and the hybrid latex had obvious core-shell structure with particle size of 155 nm. The TBOT content and the mass ratio of KH-570 to TOBT have important effect on the polymerization stability and storage stability of the hybrid latex. When the TBOT content was 5% and the mass ratio of KH-570 to TOBT was 0.6, the coagulation rate (Cr) was 3.0% and the zeta potential reached 36.1 mV. The possible formation mechanism of the hybrid latex was also proposed. 相似文献
It is the aim of this paper to describe the preparation of polysaccharide-coated nanoparticles by direct emulsion polymerization
of styrene in the presence of native dextran. In spite of the lack of surface-active properties of native dextran, stable
latexes with very low amount of coagulate were obtained. Particle size decreased with dextran concentration and molecular
weight. The amount of permanently adsorbed dextran was determined by direct titration of the polysaccharide present on the
surface of the nanoparticles. A maximum value of 2.5 mg m−2 was found. Zeta-potential measurements allowed us to estimate the thickness of the hydrophilic layer, which regularly increased
with dextran aqueous concentration. The dextran-coated polystyrene nanoparticles were stable in concentrated NaCl solutions
and could be redispersed after freeze-drying. The mechanism of chemical modification of dextran was studied by nuclear magnetic
resonance and matrix-assisted laser desorption/ionization-time of flight spectrometry studies. Graft copolymers are supposed
to be formed. 相似文献
