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Controlled Movement of Complex Double Emulsions via Interfacially Confined Magnetic Nanoparticles.

ABSTRACT: Controlled, dynamic movement of materials through noncontacting forces provides interesting opportunities in systems design. Confinement of magnetic nanoparticles to the interfaces of double emulsions introduces exceptional control of double emulsion movement. We report the selective magnetic functionalization of emulsions by the in situ selective reactions of amine-functionalized magnetic nanoparticles and oil-soluble aldehydes at only one of the double emulsion's interfaces. We demonstrate morphology-dependent macroscopic ferromagnetic behavior of emulsions induced by the interfacial confinement of the magnetic nanoparticles. The attraction and repulsion of the emulsions to applied magnetic fields results in controlled orientation changes and rotational movement. Furthermore, incorporation of liquid crystals into the double emulsions adds additional templating capabilities for precision assembly of magnetic nanoparticles, both along the interface and at point defects. Applying a magnetic field to liquid crystal complex emulsions can produce movement as well as reorganization of the director field in the droplets. The combination of interfacial chemistry and precise assembly of magnetic particles creates new systems with potentially useful field-responsive properties.

SUBMITTER: Zentner CA

PROVIDER: S-EPMC7453569 | biostudies-literature | 2020 Aug

REPOSITORIES: biostudies-literature

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Controlled Movement of Complex Double Emulsions via Interfacially Confined Magnetic Nanoparticles.

Zentner Cassandra A CA Concellón Alberto A Swager Timothy M TM

ACS central science 20200702 8

Controlled, dynamic movement of materials through noncontacting forces provides interesting opportunities in systems design. Confinement of magnetic nanoparticles to the interfaces of double emulsions introduces exceptional control of double emulsion movement. We report the selective magnetic functionalization of emulsions by the <i>in situ</i> selective reactions of amine-functionalized magnetic nanoparticles and oil-soluble aldehydes at only one of the double emulsion's interfaces. We demonstr ...[more]

PMID: 32875087

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Project description:Emulsification is a powerful, well-known technique for mixing and dispersing immiscible components within a continuous liquid phase. Consequently, emulsions are central components of medicine, food and performance materials. Complex emulsions, including Janus droplets (that is, droplets with faces of differing chemistries) and multiple emulsions, are of increasing importance in pharmaceuticals and medical diagnostics, in the fabrication of microparticles and capsules for food, in chemical separations, in cosmetics, and in dynamic optics. Because complex emulsion properties and functions are related to the droplet geometry and composition, the development of rapid, simple fabrication approaches allowing precise control over the droplets' physical and chemical characteristics is critical. Significant advances in the fabrication of complex emulsions have been made using a number of procedures, ranging from large-scale, less precise techniques that give compositional heterogeneity using high-shear mixers and membranes, to small-volume but more precise microfluidic methods. However, such approaches have yet to create droplet morphologies that can be controllably altered after emulsification. Reconfigurable complex liquids potentially have great utility as dynamically tunable materials. Here we describe an approach to the one-step fabrication of three- and four-phase complex emulsions with highly controllable and reconfigurable morphologies. The fabrication makes use of the temperature-sensitive miscibility of hydrocarbon, silicone and fluorocarbon liquids, and is applied to both the microfluidic and the scalable batch production of complex droplets. We demonstrate that droplet geometries can be alternated between encapsulated and Janus configurations by varying the interfacial tensions using hydrocarbon and fluorinated surfactants including stimuli-responsive and cleavable surfactants. This yields a generalizable strategy for the fabrication of multiphase emulsions with controllably reconfigurable morphologies and the potential to create a wide range of responsive materials.

Project description:We report the preparation of highly transparent oil-in-water Pickering emulsions using contrast-matched organic nanoparticles. This is achieved via addition of judicious amounts of either sucrose or glycerol to an aqueous dispersion of poly(glycerol monomethacrylate)56-poly(2,2,2-trifluoroethyl methacrylate)500 [PGMA-PTFEMA] diblock copolymer nanoparticles prior to high shear homogenization with an equal volume of n-dodecane. The resulting Pickering emulsions comprise polydisperse n-dodecane droplets of 20-100 ?m diameter and exhibit up to 96% transmittance across the visible spectrum. In contrast, control experiments using non-contrast-matched poly(glycerol monomethacrylate)56-poly(benzyl methacrylate)300 [PGMA56-PBzMA300] diblock copolymer nanoparticles as a Pickering emulsifier only produced conventional highly turbid emulsions. Thus contrast-matching of the two immiscible phases is a necessary but not sufficient condition for the preparation of highly transparent Pickering emulsions: it is essential to use isorefractive nanoparticles in order to minimize light scattering. Furthermore, highly transparent oil-in-water-in-oil Pickering double emulsions can be obtained by homogenizing the contrast-matched oil-in-water Pickering emulsion prepared using the PGMA56-PTFEMA500 nanoparticles with a contrast-matched dispersion of hydrophobic poly(lauryl methacrylate)39-poly(2,2,2-trifluoroethyl methacrylate)800 [PLMA39-PTFEMA800] diblock copolymer nanoparticles in n-dodecane. Finally, we show that an isorefractive oil-in-water Pickering emulsion enables fluorescence spectroscopy to be used to monitor the transport of water-insoluble small molecules (pyrene and benzophenone) between n-dodecane droplets. Such transport is significantly less efficient than that observed for the equivalent isorefractive surfactant-stabilized emulsion. Conventional turbid emulsions do not enable such a comparison to be made because the intense light scattering leads to substantial spectral attenuation.

Dataset Information

Controlled Movement of Complex Double Emulsions via Interfacially Confined Magnetic Nanoparticles.

Publications

Controlled Movement of Complex Double Emulsions via Interfacially Confined Magnetic Nanoparticles.

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