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Daeyeon Lee - One of the best experts on this subject based on the ideXlab platform.
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Janus Particles with Varying Configurations for Emulsion Stabilization
Industrial & Engineering Chemistry Research, 2019Co-Authors: Yang Lan, Je Choi, Yankai Jia, Renjing Huang, Kathleen J. Stebe, Daeyeon LeeAbstract:Analogous to molecular surfactants, amphiphilic Janus particles can function as surface active agents to stabilize emulsions. For molecular surfactants, the shape and amphiphilicity, described by packing parameters and hydrophilic–lipophilic balance (HLB), respectively, determine the type of emulsions that are produced. However, it remains unclear which features of Janus particles determine the type of emulsion that can be stabilized by these particles. In this study, a homologous series of amphiphilic Janus particles with shifting Janus boundaries and tunable chemical properties are synthesized via seeded emulsion polymerization. We systematically study the effect of the relative size of the hydrophilic domain to the total particle (configuration) and chemical nature of Janus particles on their emulsification properties. The concept of the Janus structure parameter (JSP) is introduced to describe the configuration of Janus particles. The emulsification results show that the configuration of Janus particl...
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Clickable Janus Particles
Journal of the American Chemical Society, 2016Co-Authors: Laura C. Bradley, Kathleen J. Stebe, Daeyeon LeeAbstract:Janus particles are colloidal analogues of molecular amphiphiles that can self-assemble to form diverse suprastructures, exhibit motility under appropriate catalytic reactions, and strongly adsorb to fluid–fluid interfaces to stabilize multiphasic fluid mixtures. The chemistry of Janus particles is the fundamental parameter that controls their behavior and utility as colloid surfactants in bulk solution and at fluid interfaces. To enable their widespread utilization, scalable methods that allow for the synthesis of Janus particles with diverse chemical compositions and shapes are highly desirable. Here, we develop clickable Janus particles that can be modified through thiol–yne click reactions with commercially available thiols. Janus particles are modified to be amphiphilic by introducing either carboxyl, hydroxyl, or amine moieties. We also demonstrate that regulating the extent of the modification can be used to control the particle morphology, and thus the type of emulsion stabilized, as well as to fa...
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Amphiphilic Janus particles at fluid interfaces
Soft Matter, 2013Co-Authors: Ankit Kumar, B. Jun Park, Fuquan Tu, Daeyeon LeeAbstract:Janus particles are colloids that have both hydrophilic and hydrophobic faces. Recent advances in particle synthesis enable the generation of geometrically and chemically anisotropic Janus particles with high uniformity and precision. These amphiphilic particles are similar to molecular surfactants in many aspects; they self-assemble in bulk media and also readily attach to fluid interfaces. These particles, just like molecular surfactants, could potentially function as effective stabilizers for various multiphasic systems such as emulsions and foams. In particular, just as the shape and chemical composition have a significant impact on the surfactancy of molecular amphiphiles, the ability to control the shape and wetting properties of Janus particles could provide a unique opportunity to control their surface activity. In this review, we first examine the recent developments in using amphiphilic Janus particles as colloid surfactants to stabilize multiphasic mixtures such as emulsions. These results have motivated a number of detailed investigations aimed at understanding the behaviour of Janus particles at fluid–fluid interfaces at the microscopic level, which we highlight. This review also discusses the importance of controlling the shape of Janus particles, which has a drastic impact on their behaviour at fluid interfaces. We conclude this review by presenting outlook on the future directions and outstanding problems that warrant further study to fully enable the utilization of Janus particles as colloid surfactants in practical applications.
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Equilibrium orientation of nonspherical Janus particles at fluid-fluid interfaces.
ACS nano, 2011Co-Authors: Bum Jun Park, Daeyeon LeeAbstract:We study the equilibrium orientation of nonspherical Janus particles at an oil–water interface. Two types of nonspherical Janus particles are considered: Janus ellipsoids and Janus dumbbells. To find their equilibrium orientation, we calculate and minimize the attachment energy of each Janus particle as a function of its orientation angle with respect to the oil–water interface. We find that the equilibrium orientation of the interface trapped Janus particles strongly depends on the particle characteristics, such as their size, aspect ratio, and surface properties. In general, nonspherical Janus particles adopt the upright orientation (i.e., the long axis of ellipsoids or dumbbells is perpendicular to the interface) if the difference in the wettability of the two sides is large or if the particle aspect ratio is close to 1. In contrast, Janus particles with a large aspect ratio or a small difference in the wettability of the two regions tend to have a tilted orientation at equilibrium. Moreover, we find t...
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Janus particles at an oil water interface
Soft Matter, 2011Co-Authors: Bum Jun Park, Teresa Brugarolas, Daeyeon LeeAbstract:We study the behaviour of Janus particles at an oil–water interface. Amphiphilic Janus particles exhibit attractive interactions at the fluid–fluid interface. The attractive interactions are likely due to the pinning of contact line around the diffuse boundary between the two hemispheres. The undulation of the three-phase contact line around Janus particles leads to quadrupolar capillary interactions, which we confirm by measuring the interparticle forces. We also show that Janus particles with two negatively charged-hydrophilic hemispheres show repulsive interactions.
Qingxia Liu - One of the best experts on this subject based on the ideXlab platform.
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Treatment of oily wastewaters using magnetic Janus nanoparticles of asymmetric surface wettability.
Journal of colloid and interface science, 2020Co-Authors: Qingxia LiuAbstract:Abstract Hypothesis Interfacially active magnetic Janus nanoparticles (M-Janus NPs) of asymmetric surface wettability are more interfacially active than biwettable nanoparticles (M-CMC-EC NPs) of uniform surface wettability as such that they could anchor more securely at an oil-water interface to separate emulsified oil droplets from oily wastewaters more effectively by magnetic separation. Experiments Interfacial tension and interfacial pressure-area isotherms of M-Janus NPs at oil-water interface were measured and the results were correlated to coalescence time of oil droplets determined in various types of aqueous phase (wastewaters) and to the performance of oil removal or recovery from corresponding oily wastewaters by M-Janus NPs and M-CMC-EC NPs of uniform surface wettability by an external magnetic field. Findings Despite the presence of natural/synthetic surfactants in the oily wastewaters, M-Janus NPs exhibited stronger interfacial activities and anchored more firmly at oil-water interfaces than M-CMC-EC NPs of uniform surface wettability. The application of M-Janus NPs could remove/recover >91.5% oil from oily wastewaters by an external magnetic field as compared with >84.3% achieved by M-CMC-EC NPs of uniform surface wettability for treating different oily wastewaters. The M-Janus NPs could be facilely recycled and efficiently reused in the subsequent applications to oil removal/recovery without complex regeneration.
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magnetically responsive Janus nanoparticles synthesized using cellulosic materials for enhanced phase separation in oily wastewaters and water in crude oil emulsions
Chemical Engineering Journal, 2019Co-Authors: Chen Liang, Qingxia LiuAbstract:Abstract A new class of magnetically responsive and interfacially active Janus (M−Janus) nanoparticles was designed and synthesized by sequential adsorption of cellulosic materials: hydrophobic ethyl cellulose (EC) and hydrophilic carboxymethyl cellulose (CMC) on the opposite sides of magnetite (Fe3O4) nanoparticles. The adsorption study using quartz crystal microbalance with dissipation (QCM-D) proved the concept of proposed synthesis of M−Janus nanoparticles. The adsorption of EC and CMC on magnetite nanoparticles was confirmed by zeta-potential measurements, thermogravimetric analysis (TGA), characterization using Fourier transform infrared spectroscopy (FTIR) and TEM. The surface wettabilities of the opposite sides on the M−Janus nanoparticles were investigated by measuring contact angles of nanoparticle surfaces deposited from the oil-water interfaces using the Langmuir-Blodgett method. SEM images revealed an excellent dispersion of M−Janus nanoparticles in both aqueous and organic phases. The results from the coalescence time and crumpling ratio measurement of particles-stabilized oil droplets along with the interfacial pressure-area isotherms demonstrated stronger interfacial activities of M−Janus nanoparticles and a stiffer interface with adsorbed M−Janus nanoparticles as compared with the interfaces stabilized by conventional interfacially-active nanoparticles. The microscopy images confirmed the deposition of M−Janus nanoparticles at the emulsion droplet surface during the phase separation process. The M−Janus nanoparticles not only exhibited excellent capability and high efficiency in separating emulsified water from water-in-crude oil emulsions and the oil from oily wastewaters under an external magnetic field, but also retained high interfacial activity and hence desirable separation efficiency after five-cycle applications. Because of the environmentally friendly and biodegradable cellulosic materials used in the synthesis, the M−Janus nanoparticle can achieve effective oil/water phase separation without causing further pollution to the continuous phase.
Zhenzhong Yang - One of the best experts on this subject based on the ideXlab platform.
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Janus Colloids toward Interfacial Engineering.
Langmuir : the ACS journal of surfaces and colloids, 2017Co-Authors: Fuxin Liang, Bing Liu, Zheng Cao, Zhenzhong YangAbstract:Janus colloids are functional particles consisting of two surfaces (or internal materials) with distinct physical or chemical properties in the same particle. Owing to their amphiphilic nature, Janus colloids composed of both hydrophilic and hydrophobic faces provide a powerful tool to generate functional surfaces and to manipulate the properties of interfaces. Amphiphilic Janus colloids have shown promising applications as particulate surfactants in oil/water separation, as interfacial compatibilizers in polymer blends, and as assembly blocks in robust coatings with unique wettability. In this Feature Article, we summarize recent advances in engineering interfaces by using Janus colloids.
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Polymer/Metal Segmental Janus Nanoparticles
Chinese Journal of Polymer Science, 2017Co-Authors: Lin Tang, Fuxin Liang, Qian Wang, Bingyin Jiang, Zhenzhong YangAbstract:Polymer/metal composite segmental Janus nanoparticles (NPs) are synthesized by sequential growth against poly(4-vinylpyridine) (P4VP) crosslinked cP4VP-PS Janus NPs. A Janus cluster of poly(4-vinylpyridine)-block-polystyrene (P4VP-b-PS) diblock copolymer is self-organized after absorption onto a silica patchy sphere via hydrogen bonding. Selective crosslinking of P4VP leads to the formation of robust cP4VP-PS Janus NPs. Within the cP4VP domain, functional species such as metals are preferentially grown by in situ reduction. Other thiol-capped polymers, for example, thiol-capped poly(N-isopropylacrylamide) (PNIPAM-SH), can be conjugated onto the opposite side to form polymer/metal triple segmental Janus NPs. The hyperthermia effect of Au NP of PNIPAM-Au@cP4VP-PS by near infrared (NIR) irradiation can trigger a fast transition from amphiphilic to hydrophobic of the Janus NPs at low surrounding temperature. De-stabilization of the emulsion is NIR triggered although the system temperature is below LCST (~32℃).
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Recent advances in the synthesis of Janus nanomaterials of block copolymers
Materials Chemistry Frontiers, 2017Co-Authors: Renhua Deng, Fuxin Liang, Jintao Zhu, Zhenzhong YangAbstract:We present a review of the very recent advances in the synthesis of block copolymer (BCP) Janus nanomaterials. Although Janus micelles can form by the self-assembly of BCPs in solution, patchy or core–shell structures are usually dominant. Structural transformation of the core–shell structure or disassembly of the patchy structure is further employed to achieve Janus nanomaterials. Disassembly of ABC tri-block terpolymer supramolecular structures is advantageous in tuning much more easily the shapes of the Janus nanomaterials from spherical to cylindrical and sheet/disc-like. Narrow molecular weight distributions and strict processing conditions are required. Emulsion droplet confined self-assembly of BCPs can directly achieve Janus nanomaterials in a sufficiently small droplet and/or at low polymer concentration. A neutral emulsion interface is required using proper surfactants. Alternatively, a general method has been proposed to prepare Janus nanomaterials by guided self-assembly of BCPs within a confined environment by the strong interaction and the selective crosslinking of one block. The aforementioned Janus nanomaterials are in the form of a polymer cluster. Single chain Janus nanomaterials of BCPs can be prepared by intramolecular crosslinking of one block in a very dilute solution. It remains challenging to synthesize single chain Janus nanomaterials at high solid content for example tens of percent. At the end of this review, a perspective on BCP Janus nanomaterials is provided.
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Light-Triggered Responsive Janus Composite Nanosheets
Macromolecules, 2015Co-Authors: Ziquan Cao, Fuxin Liang, Ying Chen, Guojie Wang, Zhenzhong YangAbstract:We report the synthesis of light-triggered Janus composite nanosheets and their Janus performance. Onto the amine-group terminated side of silica Janus nanosheets, a photo-responsive spiropyran-containing polymer (PSPMA) brush has been prepared by ATRP, while the other side terminated with hydrophobic octyl groups is preserved. Upon UV irradiation, the hydrophobic PSPMA side becomes hydrophilic since the hydrophobic spiropyran changes to the hydrophilic zwitterionic merocyanine form (or vice versa with visible light). Consequently, the PSPMA/silica composite nanosheets become Janus from hydrophobic or vice versa. The Janus composite nanosheets can serve as a responsive solid emulsifier, thus the stability of the emulsions can be remotely triggered with light. Unlike those pH- or temperature-responsive Janus materials, the light-triggering process requires no additional input of chemicals or thermal energy.
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Amine/acid composite Janus nanosheets
Science China. Materials, 2015Co-Authors: Qian Wang, Fuxin Liang, Xiaozhong Qu, Zhenzhong YangAbstract:Janus materials have witnessed fast development due to their diversified promising performances and practical applications. Compared with their spherical counterparts, Janus nanosheets have gained more concerns for their highly anisotropic shape besides chemistry. Herein, 3.5 nm ultrathin and flexible Janus nanosheets with carboxyl group terminated onto one side are fabricated by surface sol-gel process of the self-assembled monolayer of an amphiphilic silane onto the template CaCO3 particle firstly. Amine/acid composite Janus nanosheets are further derived from these carboxyl group terminated silica Janus nanosheets by selective conjugation with amine groups onto the other side. The amine/acid composite Janus nanosheets are dually pH responsive, and well dispersible in aqueous solution at both low and high pH levels. The nanosheets are aggregated forming multi-layered face-to-back superstructures at intermediate pH levels. This is originated by the opposite electrostatic interaction between the carboxyl and the amine groups. This approach can be extended to other silanes, and a huge family of Janus nanosheets is expected with tunable composition and performance.
Fuxin Liang - One of the best experts on this subject based on the ideXlab platform.
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Semi-IPNs Reinforced with Silica Janus Nanoparticles and Their Stress Sensing with Mechanoluminescent Probe.
Macromolecular Rapid Communications, 2020Co-Authors: Wei Yuan, Fuxin Liang, Fan Yang, Yulan ChenAbstract:A series of nanocomposite elastomers are prepared by dispersing surface-modified silica Janus nanoparticles into semi-interpenetrating network (Semi-IPN) of polyurethane/polyethyl methacrylate. Benefiting from the hierarchically crosslinked structures that consist of physical interlocking mediated by hydrogen-bond-rich silica Janus nanoparticles and permanent crosslinking by Semi-IPN, these elastomers exhibit excellent mechanical properties. Moreover, the Janus nanosheet is found more effective in strengthening and toughening the Semi-IPN, in comparison to Janus hollow sphere. Since 1,2-dioxetane is covalently embedded in these elastomers as a mechanoluminescent stress probe, stress transfer between the polymer and Janus nanoparticles and the toughening mechanism can be illuminated, which offer exciting opportunities to study the failure process of complex polymer nanocomposites with high spatial and temporal resolution.
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Janus Colloids toward Interfacial Engineering.
Langmuir : the ACS journal of surfaces and colloids, 2017Co-Authors: Fuxin Liang, Bing Liu, Zheng Cao, Zhenzhong YangAbstract:Janus colloids are functional particles consisting of two surfaces (or internal materials) with distinct physical or chemical properties in the same particle. Owing to their amphiphilic nature, Janus colloids composed of both hydrophilic and hydrophobic faces provide a powerful tool to generate functional surfaces and to manipulate the properties of interfaces. Amphiphilic Janus colloids have shown promising applications as particulate surfactants in oil/water separation, as interfacial compatibilizers in polymer blends, and as assembly blocks in robust coatings with unique wettability. In this Feature Article, we summarize recent advances in engineering interfaces by using Janus colloids.
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Polymer/Metal Segmental Janus Nanoparticles
Chinese Journal of Polymer Science, 2017Co-Authors: Lin Tang, Fuxin Liang, Qian Wang, Bingyin Jiang, Zhenzhong YangAbstract:Polymer/metal composite segmental Janus nanoparticles (NPs) are synthesized by sequential growth against poly(4-vinylpyridine) (P4VP) crosslinked cP4VP-PS Janus NPs. A Janus cluster of poly(4-vinylpyridine)-block-polystyrene (P4VP-b-PS) diblock copolymer is self-organized after absorption onto a silica patchy sphere via hydrogen bonding. Selective crosslinking of P4VP leads to the formation of robust cP4VP-PS Janus NPs. Within the cP4VP domain, functional species such as metals are preferentially grown by in situ reduction. Other thiol-capped polymers, for example, thiol-capped poly(N-isopropylacrylamide) (PNIPAM-SH), can be conjugated onto the opposite side to form polymer/metal triple segmental Janus NPs. The hyperthermia effect of Au NP of PNIPAM-Au@cP4VP-PS by near infrared (NIR) irradiation can trigger a fast transition from amphiphilic to hydrophobic of the Janus NPs at low surrounding temperature. De-stabilization of the emulsion is NIR triggered although the system temperature is below LCST (~32℃).
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Recent advances in the synthesis of Janus nanomaterials of block copolymers
Materials Chemistry Frontiers, 2017Co-Authors: Renhua Deng, Fuxin Liang, Jintao Zhu, Zhenzhong YangAbstract:We present a review of the very recent advances in the synthesis of block copolymer (BCP) Janus nanomaterials. Although Janus micelles can form by the self-assembly of BCPs in solution, patchy or core–shell structures are usually dominant. Structural transformation of the core–shell structure or disassembly of the patchy structure is further employed to achieve Janus nanomaterials. Disassembly of ABC tri-block terpolymer supramolecular structures is advantageous in tuning much more easily the shapes of the Janus nanomaterials from spherical to cylindrical and sheet/disc-like. Narrow molecular weight distributions and strict processing conditions are required. Emulsion droplet confined self-assembly of BCPs can directly achieve Janus nanomaterials in a sufficiently small droplet and/or at low polymer concentration. A neutral emulsion interface is required using proper surfactants. Alternatively, a general method has been proposed to prepare Janus nanomaterials by guided self-assembly of BCPs within a confined environment by the strong interaction and the selective crosslinking of one block. The aforementioned Janus nanomaterials are in the form of a polymer cluster. Single chain Janus nanomaterials of BCPs can be prepared by intramolecular crosslinking of one block in a very dilute solution. It remains challenging to synthesize single chain Janus nanomaterials at high solid content for example tens of percent. At the end of this review, a perspective on BCP Janus nanomaterials is provided.
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Ultrathin Janus nanodiscs
RSC Advances, 2017Co-Authors: Dan Xue, Ximing Song, Fuxin LiangAbstract:Ultrathin Janus nanodiscs with single molecular scale thickness are fabricated by self-organized sol–gel process against a patchy magnetic microsphere. Functional groups onto the patch domains can induce a favourable absorption of an amine. The morphology of Janus nanodiscs is adjusted by controlling the patchy regions on the surface of paramagnetic Fe3O4@SiO2 core/shell microspheres. The as-used patchy C8–(Fe3O4@SiO2)–PhCHO microspheres serving as templates can be easily separated from the as-formed Janus nanodiscs and reused to fabricate other Janus nanodiscs. Functional compositions such as paramagnetic Fe3O4 nanoparticles and polymers with different wettability properties are introduced onto the different regions of Janus nanodiscs to achieve magnetic Janus nanodiscs. They are used as efficient solid surfactants to stabilize emulsion.
Bum Jun Park - One of the best experts on this subject based on the ideXlab platform.
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Equilibrium orientation of nonspherical Janus particles at fluid-fluid interfaces.
ACS nano, 2011Co-Authors: Bum Jun Park, Daeyeon LeeAbstract:We study the equilibrium orientation of nonspherical Janus particles at an oil–water interface. Two types of nonspherical Janus particles are considered: Janus ellipsoids and Janus dumbbells. To find their equilibrium orientation, we calculate and minimize the attachment energy of each Janus particle as a function of its orientation angle with respect to the oil–water interface. We find that the equilibrium orientation of the interface trapped Janus particles strongly depends on the particle characteristics, such as their size, aspect ratio, and surface properties. In general, nonspherical Janus particles adopt the upright orientation (i.e., the long axis of ellipsoids or dumbbells is perpendicular to the interface) if the difference in the wettability of the two sides is large or if the particle aspect ratio is close to 1. In contrast, Janus particles with a large aspect ratio or a small difference in the wettability of the two regions tend to have a tilted orientation at equilibrium. Moreover, we find t...
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Janus particles at an oil water interface
Soft Matter, 2011Co-Authors: Bum Jun Park, Teresa Brugarolas, Daeyeon LeeAbstract:We study the behaviour of Janus particles at an oil–water interface. Amphiphilic Janus particles exhibit attractive interactions at the fluid–fluid interface. The attractive interactions are likely due to the pinning of contact line around the diffuse boundary between the two hemispheres. The undulation of the three-phase contact line around Janus particles leads to quadrupolar capillary interactions, which we confirm by measuring the interparticle forces. We also show that Janus particles with two negatively charged-hydrophilic hemispheres show repulsive interactions.
