One-Step Microfluidic Synthesis of Janus Microhydrogels with Anisotropic Thermo-Responsive Behavior and Organophilic/Hydrophilic Loading Capability

Seo, Kyoung Duck; Doh, Junsang; Kim, Dong Sung

doi:10.1021/la403015y

Cited by 42 publications

(32 citation statements)

References 30 publications

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“…A Janus compound has two surface properties, and each of these properties appears on one of two sides of the compound [1]. Janus compounds are expected to be applied as functional materials, including electronic paper [2], solid surfactants [3], optics materials [4], and drug delivery system (DDS) vectors [5]. The morphology of Janus compounds is classified into three categories: 0-dimensional compounds such as particles; one-dimensional compounds including cylinders, tubes, and rods; and two-dimensional compounds, typically sheets or discs [6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Janus Nanosheets Derived from K₄Nb₆O₁₇·3H₂O via Regioselective Interlayer Surface Modification

Suzuki¹,

Sudo²,

Hirano³

et al. 2019

Functional Materials

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Inorganic Janus nanosheets were successfully prepared using the difference in reactivity between interlayers I and II of layered hexaniobate K 4 Nb6O 17 ·3H 2 O. Janus nanosheets exhibit the highest anisotropy among Janus compounds due to their morphology. It is therefore important to prepare Janus nanosheets with stable shapes in various solvents, robust chemical bonds between nanosheets and fuctional groups and high versatility due to surface functional groups. K 4 Nb 6 O 17 ·3H 2 O, which possesses two types of interlayers and two types of organophosphonic acids that react with metal oxides to form robust covalent bonds, was employed to prepare Janus nanosheets for this study. Interlayer I was modified by octadecylphosphonic acid, followed by modification by carboxypropylphosphonic acid mainly at interlayer II. Preparation of Janus nanosheets with two organophosphonate moieties was confirmed by 31 P MAS NMR. After these regioselective and sequential modifications, the products were exfoliated into single-layered nanosheets in THF. Two types of derivatives with different repeating distances were recovered from a dispersion containing nanosheets exfoliated by different processes, centrifugation, and solvent evaporation. AFM analysis of the exfoliated nanosheets revealed that the products were Janus compounds. There are high expectations for application of these types of Janus nanosheets in various fields and for design of various Janus nanosheets using this preparation method.There are various methods of preparing Janus nanoparticles. Regioselective surface modification of nanoparticles can produce Janus nanoparticles [11]. By forming nanoparticles with two raw materials, Janus nanoparticles with different compositions can be prepared [2]. Self-assembly and subsequent cross-linking of polymer chains can also produce Janus nanoparticles [12]. Janus rods can be prepared by forming silica using TEOS by the sol-gel method on Fe 3 O 4 regioselectively [13]. Janus cylinders can be prepared by masking one side of a cylinder and conducting subsequent modification of the other side [14].Janus nanosheets exhibit the highest anisotropy among Janus compounds due to their unique morphology. They are also useful as emulsifiers, because Janus nanosheets cannot rotate at the interfaces of micelles [15]. Most Janus nanosheets reported so far have consisted of polymers. Stupp et al. reported the preparation of Janus nanosheets by polymerization of oligomers with polymerizable groups [16]. Polymerization of oligomers led to the formation of sheet morphology, because the polymerizable groups were located at the center of an oligomer. Walther et al. used triblock copolymers, polystyrene-block-polybutadiene-block-poly(tert-butyl methacrylate), for preparing Janus nanosheets [17]. Janus nanosheets were prepared by cross-linking polybutadiene domains of the triblock copolymers, and the resulting Janus nanosheets had two types of surfaces, polystyrene, and poly(tertbutyl methacrylate) moieties. These methods are based on selective polym...

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Section: Introductionmentioning

confidence: 99%

Janus Nanosheets Derived from K₄Nb₆O₁₇·3H₂O via Regioselective Interlayer Surface Modification

Suzuki¹,

Sudo²,

Hirano³

et al. 2019

Functional Materials

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“…Droplet-based microfluidic processes for the fabrication of anisotropic microgels have been accomplished using w/o emulsion droplets combined with UV-induced polymerization or ionic crosslinking to solidify the Janus droplets (on-chip or offchip) [28]. The design of the fabrication process broadly varies from (double) T-junction microfluidic devices [27,36,58], stop-flow lithography microfluidic techniques [59,60], flow-focusing microfluidic devices [30,33,38,44,61], double emulsion droplet templates [62], and single emulsion/offchip cross-linking [28]. Using this technique, magnetic and/or fluorescent components can be easily embedded in one compartment of the JPs [27,30,34,36].…”

Section: Aspects Of Environmental Sustainabilitymentioning

confidence: 99%

Janus particles: from concepts to environmentally friendly materials and sustainable applications

2020

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Janus particles represent a unique group of patchy particles combining two or more different physical or chemical functionalities at their opposite sides. Especially, individual Janus particles (JPs) with both chemical and geometrical anisotropy as well as their assembled layers provide considerable advantages over the conventional monofunctional particles or surfactant molecules offering (a) a high surface-to-volume ratio; (b) high interfacial activity; (c) target controlling and manipulation of their interfacial activity by external signals such as temperature, light, pH, or ionic strength and achieving switching between stable emulsions and macro-phase separation; (d) recovery and recycling; (e) controlling the mass transport across the interface between the two phases; and finally (f) tunable several functionalities in one particle allowing their use either as carrier materials for immobilized catalytically active substances or, alternatively, their site-selective attachment to substrates keeping another functionality active for further reactions. All these advantages of JPs make them exclusive materials for application in (bio-)catalysis and (bio-)sensing. Considering "green chemistry" aspects covering biogenic materials based on either natural or fully synthetic biocompatible and biodegradable polymers for the design of JPs may solve the problem of toxicity of some existing materials and open new paths for the development of more environmentally friendly and sustainable materials in the very near future. Considering the number of contributions published each year on the topic of Janus particles in general, the number of contributions regarding their environmentally friendly and sustainable applications is by far smaller. This certainly pinpoints an important challenge and is addressed in this review article. The first part of the review focuses on the synthesis of sustainable biogenic or biocompatible Janus particles, as well as strategies for their recovery, recycling, and reusability. The second part addresses recent advances in applications of biogenic/biocompatible and non-biocompatible JPs in environmental and biotechnological fields such as sensing of hazardous pollutants, water decontamination, and hydrogen production. Finally, we provide implications for the rational design of environmentally friendly and sustainable materials based on Janus particles.

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“…One approach is to change the volume ratio of the two Janus compartments by tuning the flow-rate ratios of the two disperse phases. For example, using this approach, poly(N-isopropylacrylamide) Janus hydrogels [15] and crescent-moon-shaped amphiphilic polymer particles [16] with controlled shapes were produced from water-in-oil (W/O) and oil-in-water (O/W) Janus droplets, respectively. Another approach is the tuning of the interfacial tensions because the morphology of a biphasic droplet comprising two immiscible phases surrounded by an external phase is determined by three interfacial tensions among the three phases [17].…”

Section: Introductionmentioning

confidence: 99%

Surfactant-Laden Janus Droplets with Tunable Morphologies and Enhanced Stability for Fabricating Lens-Shaped Polymeric Microparticles

Nisisako

2020

Micromachines

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Janus droplets can function as excellent templates for fabricating physically and chemically anisotropic particles. Here, we report new surfactant-laden Janus droplets with curvature controllability and enhanced stability against coalescence, suitable for fabricating shape-anisotropic polymer microparticles. Using a microfluidic flow-focusing device on a glass chip, nanoliter-sized biphasic droplets, comprising an acrylate monomer segment and a silicone-oil (SO) segment containing a surfactant, were produced in a co-flowing aqueous polyvinyl alcohol (PVA) solution. At equilibrium, the droplets formed a Janus geometry based on the minimization of interfacial energy, and each of the two Janus segments were uniform in size with coefficient-of-variation values below 3%. By varying the concentration of the surfactant in the SO phase, the curvature of the interface between the two lobes could be shifted among concave, planar, and convex shapes. In addition, the Janus droplets exhibited significantly improved stability against coalescence compared with previously reported Janus droplets carrying no surfactant that coalesced rapidly. Finally, via off-chip photopolymerization, concave-convex, planar-convex, and biconvex lens-shaped particles were fabricated.

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One-Step Microfluidic Synthesis of Janus Microhydrogels with Anisotropic Thermo-Responsive Behavior and Organophilic/Hydrophilic Loading Capability

Cited by 42 publications

References 30 publications

Janus Nanosheets Derived from K₄Nb₆O₁₇·3H₂O via Regioselective Interlayer Surface Modification

Janus Nanosheets Derived from K₄Nb₆O₁₇·3H₂O via Regioselective Interlayer Surface Modification

Janus particles: from concepts to environmentally friendly materials and sustainable applications

Surfactant-Laden Janus Droplets with Tunable Morphologies and Enhanced Stability for Fabricating Lens-Shaped Polymeric Microparticles

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One-Step Microfluidic Synthesis of Janus Microhydrogels with Anisotropic Thermo-Responsive Behavior and Organophilic/Hydrophilic Loading Capability

Cited by 42 publications

References 30 publications

Janus Nanosheets Derived from K4Nb6O17·3H2O via Regioselective Interlayer Surface Modification

Janus Nanosheets Derived from K4Nb6O17·3H2O via Regioselective Interlayer Surface Modification

Janus particles: from concepts to environmentally friendly materials and sustainable applications

Surfactant-Laden Janus Droplets with Tunable Morphologies and Enhanced Stability for Fabricating Lens-Shaped Polymeric Microparticles

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Product

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Janus Nanosheets Derived from K₄Nb₆O₁₇·3H₂O via Regioselective Interlayer Surface Modification

Janus Nanosheets Derived from K₄Nb₆O₁₇·3H₂O via Regioselective Interlayer Surface Modification