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Hunter SJ, Thompson KL, Lovett JR, Hatton FL, Derry MJ, Lindsay C, Taylor P, Armes SP. Synthesis, Characterization, and Pickering Emulsifier Performance of Anisotropic Cross-Linked Block Copolymer Worms: Effect of Aspect Ratio on Emulsion Stability in the Presence of Surfactant. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:254-265. [PMID: 30562037 DOI: 10.1021/acs.langmuir.8b03727] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization is used to prepare epoxy-functional PGMA-P(HPMA- stat-GlyMA) diblock copolymer worms, where GMA, HPMA, and GlyMA denote glycerol monomethacrylate, 2-hydroxypropyl methacrylate, and glycidyl methacrylate, respectively. The epoxy groups on the GlyMA residues were ring-opened using 3-aminopropyltriethoxysilane (APTES) in order to cross-link the worm cores via a series of hydrolysis-condensation reactions. Importantly, the worm aspect ratio can be adjusted depending on the precise conditions selected for covalent stabilization. Relatively long cross-linked worms are obtained by reaction with APTES at 20 °C, whereas much shorter worms with essentially the same copolymer composition are formed by cooling the linear worms from 20 to 4 °C prior to APTES addition. Small-angle X-ray scattering (SAXS) studies confirmed that the mean aspect ratio for the long worms is approximately eight times greater than that for the short worms. Aqueous electrophoresis studies indicated that both types of cross-linked worms acquired weak cationic surface charge at low pH as a result of protonation of APTES-derived secondary amine groups within the nanoparticle cores. These cross-linked worms were evaluated as emulsifiers for the stabilization of n-dodecane-in-water emulsions via high-shear homogenization at 20 °C and pH 8. Increasing the copolymer concentration led to a reduction in mean droplet diameter, indicating that APTES cross-linking was sufficient to allow the nanoparticles to adsorb intact at the oil/water interface and hence produce genuine Pickering emulsions, rather than undergo in situ dissociation to form surface-active diblock copolymer chains. In surfactant challenge studies, the relatively long worms required a thirty-fold higher concentration of a nonionic surfactant (Tween 80) to be displaced from the n-dodecane-water interface compared to the short worms. This suggests that the former nanoparticles are much more strongly adsorbed than the latter, indicating that significantly greater Pickering emulsion stability can be achieved by using highly anisotropic worms. In contrast, colloidosomes prepared by reacting the hydroxyl-functional adsorbed worms with an oil-soluble polymeric diisocyanate remained intact when exposed to high concentrations of Tween 80.
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Affiliation(s)
- Saul J Hunter
- Department of Chemistry , University of Sheffield , Dainton Building, Brook Hill , Sheffield , Yorkshire S3 7HF , U.K
| | - Kate L Thompson
- The School of Materials, University of Manchester , Oxford Road , Manchester M13 9PL , U.K
| | - Joseph R Lovett
- Department of Chemistry , University of Sheffield , Dainton Building, Brook Hill , Sheffield , Yorkshire S3 7HF , U.K
| | - Fiona L Hatton
- Department of Chemistry , University of Sheffield , Dainton Building, Brook Hill , Sheffield , Yorkshire S3 7HF , U.K
| | - Matthew J Derry
- Department of Chemistry , University of Sheffield , Dainton Building, Brook Hill , Sheffield , Yorkshire S3 7HF , U.K
| | - Christopher Lindsay
- Syngenta, Jealott's Hill International Research Centre , Bracknell , Berkshire RG42 6EY , U.K
| | - Philip Taylor
- Syngenta, Jealott's Hill International Research Centre , Bracknell , Berkshire RG42 6EY , U.K
| | - Steven P Armes
- Department of Chemistry , University of Sheffield , Dainton Building, Brook Hill , Sheffield , Yorkshire S3 7HF , U.K
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Wu D, Mihali V, Honciuc A. pH-Responsive Pickering Foams Generated by Surfactant-Free Soft Hydrogel Particles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:212-221. [PMID: 30540483 DOI: 10.1021/acs.langmuir.8b03342] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Pickering foams are foams stabilized by particles and are generally known to have good stability. A special subclass of particle-stabilized foams includes stimuli-responsive Pickering foams that can be formed or deconstructed by applying an external stimuli or changing the environmental conditions; such intelligent particles could find use in many practical applications. Here, we synthesized surfactant-free biocompatible poly[2(diethylamino)ethyl methacrylate] (PDEAEMA) hydrogel particles (HGPs) by emulsion polymerization. The morphology, structure, and surface charge of the HGPs were characterized by TEM, DLS, and the zeta potential, respectively. We have observed that the pH values of the aqueous solution have a strong influence on the formation of the Pickering foams in the presence of PDEAEMA HGPs. Namely, at pH values ≤4.0 no Pickering foams were produced, while at pH values >4.0 stable Pickering foams were formed. Moreover, the height, size and bubble size distribution of Pickering foams are strongly influenced by the pH values of aqueous solution and PDEAEMA HGPs concentration. The formed Pickering foams in basic aqueous solution can all be conveniently deconstructed by changing the pH values to below 4.0. Interestingly, the dried lamellas of the Pickering foams were constituted by either monolayers or multilayers of PDEAEMA HGPs as demonstrated by SEM.
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Affiliation(s)
- Dalin Wu
- Institute of Chemistry and Biotechnology , Zurich University of Applied Sciences , Einsiedlerstrasse 31 , 8820 Waedenswil , Switzerland
| | - Voichita Mihali
- Institute of Chemistry and Biotechnology , Zurich University of Applied Sciences , Einsiedlerstrasse 31 , 8820 Waedenswil , Switzerland
| | - Andrei Honciuc
- Institute of Chemistry and Biotechnology , Zurich University of Applied Sciences , Einsiedlerstrasse 31 , 8820 Waedenswil , Switzerland
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Shi Y, Xiong D, Chen Y, Wang H, Wang J. CO2-responsive Pickering emulsions stabilized by in-situ generated ionic liquids and silica nanoparticles. J Mol Liq 2019. [DOI: 10.1016/j.molliq.2018.10.096] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Koroleva MY, Bydanov DA, Palamarchuk KV, Yurtov EV. Stabilization of Oil-in-Water Emulsions with SiO2 and Fe3O4 Nanoparticles. COLLOID JOURNAL 2018. [DOI: 10.1134/s1061933x18030080] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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Ren G, Wang M, Wang L, Wang Z, Chen Q, Xu Z, Sun D. Dynamic Covalent Silica Nanoparticles for pH-Switchable Pickering Emulsions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:5798-5806. [PMID: 29709197 DOI: 10.1021/acs.langmuir.8b00757] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Dynamic covalent surfactants have been recently reported for preparation of pH-switchable emulsions [ Sun , D. Langmuir , 2017 , 33 , 3040 ]. In this study, dynamic covalent silica (SiO2-B) nanoparticles of switchable wettability were fabricated by a pH-responsive dynamic (covalent) imine bond between hydrophilic amino silica (SiO2-NH2) nanoparticles and hydrophobic benzaldehyde molecules. The properties of SiO2-B were characterized by Fourier transform infrared spectroscopy, elemental analysis, contact angle measurement, and ζ potential measurement. The hydrophilicity and hydrophobicity of SiO2-B were shown to be readily switchable by adjusting pH between 7.8 and 3.5. At pH 7.8, SiO2-B was partially hydrophobic and adsorbed at oil-water interface to stabilize O/W Pickering emulsions, which were characterized by electrical conductivity, optical microscopy, and confocal laser scanning microscopy. Upon lowering the pH to 3.5, the dynamic covalent bond is dissociated to convert partially hydrophobic SiO2-B into highly hydrophilic SiO2-NH2 and surface-inactive benzaldehyde. Both of them desorb from oil-water interface, resulting in a rapid oil-water separation of the Pickering emulsions. Alternating stabilization and phase separation of the Pickering emulsions over 3 cycles were demonstrated by adjusting the pH. The pH-switchable Pickering emulsions show great potential in application to effective oil-water separation of emulsions.
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Affiliation(s)
- Gaihuan Ren
- Key Laboratory of Colloid and Interface Chemistry, Ministry of Education , Shandong University , Jinan , Shandong 250100 , P. R. China
| | - MaoXin Wang
- Key Laboratory of Colloid and Interface Chemistry, Ministry of Education , Shandong University , Jinan , Shandong 250100 , P. R. China
| | - Lei Wang
- College of Chemistry and Molecular Engineering , Qingdao University of Science & Technology , Qingdao 266042 , P. R. China
| | - Zengzi Wang
- Key Laboratory of Colloid and Interface Chemistry, Ministry of Education , Shandong University , Jinan , Shandong 250100 , P. R. China
| | - Qianqian Chen
- Key Laboratory of Colloid and Interface Chemistry, Ministry of Education , Shandong University , Jinan , Shandong 250100 , P. R. China
| | - Zhenghe Xu
- Department of Chemical and Materials Engineering , University of Alberta , Edmonton , Alberta , Canada T6G 2V4
- Institute of Nuclear and New Energy Technology , Tsinghua University , Beijing 1000084 , P. R. China
| | - Dejun Sun
- Key Laboratory of Colloid and Interface Chemistry, Ministry of Education , Shandong University , Jinan , Shandong 250100 , P. R. China
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Hua X, Frechette J, Bevan MA. Nanoparticle adsorption dynamics at fluid interfaces. SOFT MATTER 2018; 14:3818-3828. [PMID: 29718061 DOI: 10.1039/c8sm00273h] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Understanding the dynamic adsorption of nanoparticles (NPs) at fluid interfaces is important for stabilizing emulsions and for the preparation of 2D NP-based materials. Here we show that the Ward-Tordai equations commonly employed to describe the dynamics of surfactant adsorption at a fluid interface combined with a Frumkin adsorption isotherm can be employed to model the diffusion-limited adsorption of NPs onto a fluid interface. In contrast to surfactants, an additional wetting equation of state (EOS) must be incorporated to characterize the dynamic interfacial tension during the adsorption of NPs to the oil-water interface. Our results show agreement between the model and experiments with NP area fractions <0.3. Slower dynamics are observed at larger area fractions, which are speculated to arise from polydispersity or re-organization at the interface. We show the model can be extended to the competitive adsorption between the NPs and a surface active species.
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Affiliation(s)
- Xiaoqing Hua
- Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD 21218, USA.
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Lin Q, Liu KH, Cui ZG, Pei XM, Jiang JZ, Song BL. pH-Responsive Pickering foams stabilized by silica nanoparticles in combination with trace amount of dodecyl dimethyl carboxyl betaine. Colloids Surf A Physicochem Eng Asp 2018. [DOI: 10.1016/j.colsurfa.2018.02.027] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Chen R, Ren N, Jin X, Zhu X. Stabilization capacity of PNIPAM microgels as particulate stabilizer in dispersion polymerization. Colloids Surf A Physicochem Eng Asp 2018. [DOI: 10.1016/j.colsurfa.2017.11.069] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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Chen J, Zhu C, Yang Z, Wang P, Yue Y, Kitaoka T. Thermally Tunable Pickering Emulsions Stabilized by Carbon-Dot-Incorporated Core-Shell Nanospheres with Fluorescence "On-Off" Behavior. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:273-283. [PMID: 29227679 DOI: 10.1021/acs.langmuir.7b03490] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Lack of deep understanding of nanoparticle (NP) actions at oil/water interface set an obstacle to practical applications of Pickering emulsions. Fluorescence labels fabricated by incorporation of carbon dots (CDs) into poly(N-isopropylacrylamide) (PNIPAM) matrix can not only mark the action of PNIPAM-based NPs in the interface but also reflect the colloidal morphologies of PNIPAM. In this work, we employed coaxial electrospraying for fabricating core-shell nanospheres of cellulose acetate encapsulated by PNIPAM, and facile incorporation of CDs in PNIPAM shells was achieved simultaneously. The coaxial electrosprayed NPs (CENPs) with temperature-dependent wettability can stabilize heptane and toluene in water at 25 °C, respectively, and reversible emulsion break can be triggered by temperature adjustment around the low critical solution temperature (LCST). Remarkably, CENP/CD composites exhibited a fluorescence "on-off" behavior because of the volume phase transition of the PNIPAM shell. CENP/CD composites in Pickering emulsions clearly elucidated the motions of CENPs in response to temperature changes. At temperatures below the LCST, the CENP concentration played an important role in surface coverage of oil droplets. Specifically, the CENP concentration above the minimum concentration for complete emulsification of oil phase led to high surface coverage and two-domain adsorption of CENPs at the interface including primary monolayer anchoring of CENPs on droplets surrounded by interconnected CENP networks, which contributed to the superior stability of the emulsions. Moreover, CENP/CD composites can be recycled with well-preserved core-shell structure and stable fluorescent properties, which offers their great potential applications in sensors and imaging.
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Affiliation(s)
- Jianqiang Chen
- Laboratory of Advanced Environmental & Energy Storage Materials, Department of Environment Engineering, Nanjing Forestry University , 159 Longpan Road, Nanjing 210037, P. R. China
| | - Chenyang Zhu
- Laboratory of Advanced Environmental & Energy Storage Materials, Department of Environment Engineering, Nanjing Forestry University , 159 Longpan Road, Nanjing 210037, P. R. China
| | - Zhen Yang
- School of Chemistry and Materials Science, Jiangsu Provincial Key Laboratory of Material Cycling and Pollution Control, Nanjing Normal University , 1 Wenyuan Road, Nanjing 210023, P. R. China
| | - Ping Wang
- Laboratory of Advanced Environmental & Energy Storage Materials, Department of Environment Engineering, Nanjing Forestry University , 159 Longpan Road, Nanjing 210037, P. R. China
| | - Yiying Yue
- Laboratory of Advanced Environmental & Energy Storage Materials, Department of Environment Engineering, Nanjing Forestry University , 159 Longpan Road, Nanjing 210037, P. R. China
| | - Takuya Kitaoka
- Department of Agro-Environmental Sciences, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University , 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
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Kaptay G. On the Negative Surface Tension of Solutions and on Spontaneous Emulsification. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:10550-10560. [PMID: 28918625 DOI: 10.1021/acs.langmuir.7b01968] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The condition of negative surface tension of a binary regular solution is discussed in this paper using the recently reconfirmed Butler equation (Langmuir 2015, 31, 5796-5804). It is shown that the surface tension becomes negative only for solutions with strong repulsion between the components. This repulsion for negative surface tension should be so strong that this phenomenon appears only within a miscibility gap, that is, in a two-phase region of macroscopic liquid solutions. Thus, for a macroscopic solution, the negative surface tension is possible only in a nonequilibrium state. However, for a nano-solution, negative surface tension is also possible in equilibrium state. It is also shown that nano- and microemulsions can be thermodynamically stable against both coalescence and phase separation. Further, the thermodynamic theory of emulsion stability is developed for a three-component (A-B-C) system with A-rich droplets dispersed in a C-rich matrix, separated by the segregated B-rich layer (the solubility of B is limited in both A and C while the mutual solubility of A and C is neglected). It is shown that when a critical droplet size is achieved by forced emulsification, it is replaced by spontaneous emulsification and the droplet size is reduced further to its equilibrium value. The existence of maximum temperature of emulsion stability is shown. Using low-energy emulsification below this maximum temperature, spontaneous emulsification can appear, which is enhanced with further decrease of temperature. This finding can be applied to interpret the experimental observations on spontaneous emulsification or for the design of stable micro- and nanoemulsions.
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Affiliation(s)
- George Kaptay
- Department of Nanotechnology, University of Miskolc , Egyetemvaros, Miskolc 3515, Hungary
- MTA-ME Materials Science Research Group , Egyetemvaros, Miskolc 3515, Hungary
- Bay Zoltan Ltd on Applied Research, BAY-ENG , 2 Igloi, Miskolc 3519, Hungary
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