Polymeric Particles with Structural Complexity from Stable Immobilized Emulsions (original) (raw)
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In this paper, we demonstrated a unique and simple method for fabricating colloidal particles of complex structures using oil-in-water emulsion droplets as confined geometries. A variety of structural motifs were produced using binary colloids of microspheres of polystyrene (PS) or silica and nanosized particles as the second component. When PS or silica microspheres and PS macromolecules were dispersed in oil-in-water emulsion droplets, particles with well-coordinated patches were obtained because the PS macromolecules partially covered the microsphere clusters. When silica or gold nanoparticles were dispersed together with the PS microspheres in oil-in-water emulsion droplets instead of PS macromolecules, composite particles with patches were obtained. In this case, silica or gold shell structures with well-coordinated windows were produced by selectively removing the large PS microspheres from the organic-inorganic composite clusters.
Macroporous polymers from particle-stabilized emulsions
Macroporous polymers are attractive materials due to their low density, low cost, recyclability and tunable mechanical and functional properties. Here, we report a new approach to prepare macroporous polymers from emulsions stabilized with colloidal polymeric particles in the absence of chemical reactions. Stable water-in-oil emulsions were prepared using poly(vinylidene difluoride) (PVDF), poly(tetrafluoroethylene) (PTFE), and poly(etheretherketone) (PEEK) as stabilizing polymeric particles in emulsions. The partial wetting of the polymeric particles by the two immiscible liquids drives particles at the water–oil interface during emulsification, leading to extremely stable water-in-oil emulsions. The particle-stabilized emulsions were processed into highly porous solid polymer components upon drying and sintering. The high stability of emulsions also allows for the preparation of hollow polymeric microcapsules. We describe the conditions required for the adsorption of particles at the liquid–liquid interface, we show the rheological behavior of the polymer-loaded wet emulsions and, we discuss the effect of the emulsions' initial compositions on the final sintered porous structures. This new approach for the fabrication of macroporous PVDF, PTFE, and PEEK polymers is particularly suited for the preparation of porous materials from intractable polymers but can also be easily applied to a variety of other polymeric particles.
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Journal of Applied Polymer Science, 2007
The self-assembly of pH-responsive poly (methyl methacrylate-co-acrylic acid) latex particles at emulsion droplet interfaces was achieved. Raising pH increases the hydrophilicity of the latex particles in situ and the latex particle acts as an efficient particulate emulsifier self-assembling at emulsion droplet interface at around pH 10-11 but exhibits no emulsifier activity at higher pH. This effect can be reversibly induced simply by varying the aqueous phase pH and thus the latex emulsifier can be reassembled. The effect factors, including the aqueous phase pH, the surface carboxyl content, z-Potential of the latex particles and oil phase solvent have been investigated. Using monomer as oil phase, the latex particles could stabilize emulsion droplets during polymerization and cage-like polymer microspheres with hollow core/porous shell structure were obtained after polymerization. The mechanism of the latex particles self-assembly was discussed. The morphologies of emulsion and microspheres were characterized by optical microscopy, scanning electron microscopy, and transmission electron microscopy.
Macroporous-polymers-from-particle-stabilized-emulsions_2009_Polymer.pdf
Macroporous polymers are attractive materials due to their low density, low cost, recyclability and tunable mechanical and functional properties. Here, we report a new approach to prepare macroporous polymers from emulsions stabilized with colloidal polymeric particles in the absence of chemical reactions. Stable water-in-oil emulsions were prepared using poly(vinylidene difluoride) (PVDF), poly(tetrafluoroethylene) (PTFE), and poly(etheretherketone) (PEEK) as stabilizing polymeric particles in emulsions. The partial wetting of the polymeric particles by the two immiscible liquids drives particles at the water-oil interface during emulsification, leading to extremely stable water-in-oil emulsions. The particle-stabilized emulsions were processed into highly porous solid polymer components upon drying and sintering. The high stability of emulsions also allows for the preparation of hollow polymeric microcapsules. We describe the conditions required for the adsorption of particles at the liquid-liquid interface, we show the rheological behavior of the polymer-loaded wet emulsions and, we discuss the effect of the emulsions' initial compositions on the final sintered porous structures. This new approach for the fabrication of macroporous PVDF, PTFE, and PEEK polymers is particularly suited for the preparation of porous materials from intractable polymers but can also be easily applied to a variety of other polymeric particles.
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Pickering stabilization by colloidal particles is a common strategy to disperse droplets of one fluid into another fluid in food, cosmetics and chemical industries1-3. For over a century, this kind of stabilization has been governed by constant surface coverage concepts in which particles irreversibly attach to the fluid–fluid interface. The need to cover sufficient interfacial area to prevent coalescence typically results in large loadings of particles, uniform droplet size, creation of rigid interface and closed-cell structure with small total area4-7. Here we report a stabilization mechanism that yields hierarchically structured oil-in-brine emulsions with high interfacial area, deformability, connectivity and long-term stability at unprecedentedly low nanoparticle loadings. The hierarchy in structure is achieved via dynamic cation-particle-droplet interactions in cascaded emulsification, which consists of i) formation of submicron oil droplets (~250 nm) lightly covered by hydrop...
Colloid-stabilized emulsions: behaviour as the interfacial tension is reduced
Journal of Physics: Condensed Matter, 2005
We present confocal microscopy studies of novel particle-stabilized emulsions. The novelty arises because the immiscible fluids have an accessible upper critical solution temperature. The emulsions have been created by beginning with particles dispersed in the single-fluid phase. On cooling, regions of the minority phase nucleate. While coarsening these nuclei become coated with particles due to the associated reduction in interfacial energy. The resulting emulsion is arrested, and the particle-coated interfaces have intriguing properties. Having made use of the binary-fluid phase diagram to create the emulsion we then make use of it to study the properties of the interfaces. As the emulsion is re-heated toward the single-fluid phase the interfacial tension falls and the volume of the dispersed phase drops. Crumpling, fracture or coalescence can follow. The results show that the elasticity of the interfaces has a controlling influence over the emulsion behaviour.
Nanosized Emulsions Stabilized by Semisolid Polymer Interphase
Langmuir, 2010
We introduce a new approach for stabilizing oil-in-water nanoemulsions using a semisolid interphase formed by the phase separation of amphiphilic block copolymers from the organic phase. This system is illustrated using an amphiphilic diblock copolymer, poly(ethylene oxide)-block-poly(ε-caprolactone) (PEO-b-PCL), with commonly used oils. PEO-b-PCL can be miscible with oil at elevated temperatures (70-80°C); however, polymer/oil demixing occurs as the temperature drops below the melting temperature of PEO-b-PCL (∼55°C). A homogeneous polymer/oil mixture was dispersed in water at 80°C to generate embryonic emulsions, and then the emulsion size was reduced to a nanometer range through microfluidic homogenization. The structure of the generated nanoemulsions is irreversibly frozen as they are cooled down to ambient temperature. The nanoemulsions stabilized by PEO-b-PCL show the excellent colloidal stability against thermal and chemical stresses, exhibiting no significant changes in the size distribution during incubation for 4 months at ambient temperature or 10 days at 60°C. This study demonstrates that PEO-b-PCL is an attractive emulsifying material for practical nanoemulsion formulations requiring structural stability under a broad range of conditions.