2021 |
Johnson EC, Gresham IJ, Prescott SW, Nelson A, Wanless EJ, Webber GB, 'The direction of influence of specific ion effects on a pH and temperature responsive copolymer brush is dependent on polymer charge', Polymer, 214 (2021)
© 2020 Elsevier Ltd The effect of electrolyte identity on the conformation of homopolymer brushes of poly(2-(2-methoxyethoxy) ethyl methacrylate) (PMEO2MA) and poly(2-(diethylamin... [more]
© 2020 Elsevier Ltd The effect of electrolyte identity on the conformation of homopolymer brushes of poly(2-(2-methoxyethoxy) ethyl methacrylate) (PMEO2MA) and poly(2-(diethylamino)ethyl methacrylate) (PDEA), as well as a P(MEO2MA-co-DEA) copolymer brush of 90:10 mol% composition has been examined. PMEO2MA is a thermoresponsive polymer with a lower critical solution temperature of ~28 °C, PDEA a weak polybase with an apparent pKa of ~7.5, while the copolymer brush exhibits both pH and temperature responsive behaviour. Brushes were synthesised using surface initiated ARGET ATRP. The effect of temperature at low and high pH in the presence of different electrolytes on the thickness of the P(MEO2MA-co-DEA) 90:10 mol% brush was tracked with ellipsometry and the polymer volume fraction profile was elucidated with neutron reflectometry. The effect of each electrolyte on the copolymer brush conformation as the temperature changes could be switched by changing the pH from low (charged DEA segments) to high (uncharged DEA segments). The overall behaviour of the copolymer in each salt was PDEA-like at low pH, and MEO2MA-like at high pH. At low pH a reverse Hofmeister effect was observed, while at high pH a direct Hofmeister effect was observed.
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2021 |
Robertson H, Johnson EC, Gresham IJ, Prescott SW, Nelson A, Wanless EJ, Webber GB, 'Competitive specific ion effects in mixed salt solutions on a thermoresponsive polymer brush.', J Colloid Interface Sci, 586 292-304 (2021)
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2020 |
Lobel BT, Ireland PM, Walsh LM, Thomas CA, Webber GB, Wanless EJ, 'Electrostatic Transfer of Conductive Particles for the Formation of Liquid Marbles-Charge Transfer Behavior', Journal of Physical Chemistry C, 124 9947-9957 (2020) [C1]
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2020 |
McLean B, Webber GB, Page AJ, 'Energy and Charge Transfer at the Boron Nitride Nanotube - Catalyst Growth Interface', Journal of Physical Chemistry C, 124 11662-11668 (2020) [C1]
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2020 |
Thomas CA, Munday H, Lobel BT, Asaumi Y, Fujii S, Ireland PM, et al., 'Exploring the Impact of Particle Material Properties on Electrostatic Liquid Marble Formation', Journal of Physical Chemistry C, 124 26258-26267 (2020) [C1]
© 2020 American Chemical Society. Specific particle material properties such as conductivity, cohesion, and density have been neither directly nor thoroughly studied regarding par... [more]
© 2020 American Chemical Society. Specific particle material properties such as conductivity, cohesion, and density have been neither directly nor thoroughly studied regarding particle behavior in an electrostatic field and the follow-on impact this has on the electrostatic formation of liquid marbles. In this method, an applied electric field drives the extraction of particles from a bed and their transport to a pendent, earthed water droplet. Herein, prior studies of electrostatic formation of particle-stabilized droplets and liquid marbles have been expanded to compare the impact of density using the spherical polystyrene (PS) latex and glass particles of similar shape and size. The addition of thin polymer shells to both samples, which increases the conductivity and cohesion, allows the interplay of these three properties to be examined systematically. Separation distances between the particle bed and the droplet from which particles can initially be extracted increase as the negative applied potential increases. Initial extraction distances of both core particles were found to be similar, ~1.5 mm at 2.0 kV applied potential, despite the greater density, and thus mass of the glass particles. It is demonstrated that this is a result of competitive interactions between particle density, conductivity, and cohesion; PS is less conductive and more cohesive than glass. Introducing a polypyrrole shell increases the separation distance for extraction to approximately 4 mm for PS core particles but has little impact on glass core particles, demonstrating that for particles with constant conductivity and cohesion reducing the density facilitates extraction. Modeling and quantification of extraction threshold forces for each particle type were undertaken, utilizing the measurement of a radially symmetric area of the particle bed from which particles were observed in the initial extraction stages. This measurement highlighted that it is significantly easier to extract PS compared to glass, with particles extracted from a region in the bed up to 5 times the width in the PS case. Particle density is hypothesized to not be the determining factor in the stabilization of the coated liquid droplets; therefore, the interplay of a multitude of physical properties must be considered when determining the suitability of particulate materials for this electrostatic method.
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2020 |
Johnson EC, Willott JD, de Vos WM, Wanless EJ, Webber GB, 'Interplay of Composition, pH, and Temperature on the Conformation of Multi-stimulus-responsive Copolymer Brushes: Comparison of Experiment and Theory.', Langmuir : the ACS journal of surfaces and colloids, 36 5765-5777 (2020) [C1]
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2020 |
Johnson EC, Willott JD, Gresham IJ, Murdoch TJ, Humphreys BA, Prescott SW, et al., 'Enrichment of Charged Monomers Explains Non-monotonic Polymer Volume Fraction Profiles of Multi-stimulus Responsive Copolymer Brushes.', Langmuir : the ACS journal of surfaces and colloids, 36 12460-12472 (2020) [C1]
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2019 |
Stefanovic R, Chen Z, FitzGerald PA, Warr GG, Atkin R, Page AJ, Webber GB, 'Effect of halides on the solvation of poly(ethylene oxide) in the ionic liquid propylammonium nitrate.', Journal of Colloid and Interface Science, 534 649-654 (2019) [C1]
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2019 |
McLean B, Webber GB, Page AJ, 'Boron Nitride Nanotube Nucleation via Network Fusion during Catalytic Chemical Vapor Deposition.', Journal of the American Chemical Society, 141 13385-13393 (2019) [C1]
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2019 |
Wanless EJ, Webber GB, Fujii S, 'Particles at Fluid Interfaces', FRONTIERS IN CHEMISTRY, 7 (2019)
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2019 |
Humphreys BA, Prescott SW, Murdoch TJ, Nelson A, Gilbert EP, Webber GB, Wanless EJ, 'Influence of molecular weight on PNIPAM brush modified colloidal silica particles', SOFT MATTER, 15 55-64 (2019) [C1]
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2019 |
McLean B, Webber GB, Page AJ, 'Boron Nitride Nanotube Nucleation during Ni-Catalyzed Boron Oxide Chemical Vapor Deposition', Journal of Physical Chemistry C, 123 27875-27883 (2019) [C1]
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2019 |
Willott JD, Humphreys BA, Webber GB, Wanless EJ, De Vos WM, 'Combined Experimental and Theoretical Study of Weak Polyelectrolyte Brushes in Salt Mixtures', Langmuir, 35 2709-2718 (2019) [C1]
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2019 |
Johnson EC, Murdoch TJ, Gresham IJ, Humphreys BA, Prescott SW, Nelson A, et al., 'Temperature dependent specific ion effects in mixed salt environments on a thermoresponsive poly(oligoethylene glycol methacrylate) brush', Physical chemistry chemical physics : PCCP, 21 4650-4662 (2019) [C1]
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2019 |
Stefanovic R, Webber GB, Page AJ, 'Polymer solvation in choline chloride deep eutectic solvents modulated by the hydrogen bond donor', Journal of Molecular Liquids, 279 584-593 (2019) [C1]
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2019 |
Thomas CA, Kasahara M, Asaumi Y, Lobel BT, Fujii S, Ireland PM, et al., 'Influence of particle size on extraction from a charged bed - toward liquid marble formation', SOFT MATTER, 15 7547-7556 (2019) [C1]
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2019 |
Gregory KP, Webber GB, Wanless EJ, Page AJ, 'Lewis Strength Determines Specific-Ion Effects in Aqueous and Nonaqueous Solvents.', The Journal of Physical Chemistry. A, 123 6420-6429 (2019) [C1]
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2019 |
Kawata Y, Thomas CA, Asaumi Y, Hanochi H, Ireland PM, Fujii S, et al., 'Electrostatic Formation of Liquid Marbles Using Thermo-responsive Polymer-coated Particles', CHEMISTRY LETTERS, 48 578-581 (2019) [C1]
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2019 |
Humphreys BA, Johnson EC, Wanless EJ, Webber GB, 'Poly(N-isopropylacrylamide) Response to Salt Concentration and Anion Identity: A Brush-on-Brush Study', LANGMUIR, 35 10818-10830 (2019) [C1]
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2018 |
Kido K, Ireland PM, Sekido T, Wanless EJ, Webber GB, Nakamura Y, Fujii S, 'Formation of Liquid Marbles Using pH-Responsive Particles: Rolling vs Electrostatic Methods', LANGMUIR, 34 4970-4979 (2018) [C1]
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2018 |
Humphreys BA, Wanless EJ, Webber GB, 'Effect of ionic strength and salt identity on poly(N-isopropylacrylamide) brush modified colloidal silica particles', Journal of Colloid and Interface Science, 516 153-161 (2018) [C1]
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2018 |
Murdoch TJ, Humphreys BA, Johnson EC, Prescott SW, Nelson A, Wanless EJ, Webber GB, 'The role of copolymer composition on the specific ion and thermo-response of ethylene glycol- based brushes', POLYMER, 138 229-241 (2018) [C1]
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2018 |
Stefanovic R, Webber GB, Page AJ, 'Nanostructure of propylammonium nitrate in the presence of poly(ethylene oxide) and halide salts', Journal of Chemical Physics, 148 193826-1-193826-14 (2018) [C1]
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2018 |
Ireland PM, Kido K, Webber G, Fujii S, Wanless E, 'pH-Responsive Particle-Liquid Aggregates Electrostatic Formation Kinetics', Frontiers in Chemistry, 6 1-8 (2018) [C1]
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2018 |
Cooper PK, Li H, Yepuri NR, Nelson A, Webber GB, Le Brun AP, et al., 'Ionic Liquid Adsorption at the Silica-Oil Interface Revealed by Neutron Reflectometry', Journal of Physical Chemistry C, 122 24077-24084 (2018) [C1]
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2018 |
Thomas CA, Kido K, Kawashima H, Fujii S, Ireland PM, Webber GB, Wanless EJ, 'Electrostatic Formation of Polymer Particle Stabilised Liquid Marbles and Metastable Droplets - Effect of Latex Shell Conductivity', Journal of Colloid and Interface Science, 529 486-495 (2018) [C1]
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2018 |
Murdoch TJ, Humphreys BA, Johnson EC, Webber GB, Wanless EJ, 'Specific ion effects on thermoresponsive polymer brushes: Comparison to other architectures', Journal of Colloid and Interface Science, 526 429-450 (2018) [C1]
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2018 |
Ireland PM, Thomas CA, Lobel BT, Webber GB, Fujii S, Wanless EJ, 'An Electrostatic Method for Manufacturing Liquid Marbles and Particle-Stabilized Aggregates', FRONTIERS IN CHEMISTRY, 6 (2018) [C1]
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2018 |
McLean B, Webber GB, Page AJ, 'Boron Nitride Nucleation Mechanism during Chemical Vapor Deposition', Journal of Physical Chemistry C, 122 24341-24349 (2018) [C1]
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2017 |
Stefanovic R, Ludwig M, Webber GB, Atkin R, Page AJ, 'Nanostructure, hydrogen bonding and rheology in choline chloride deep eutectic solvents as a function of the hydrogen bond donor', PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 19 3297-3306 (2017) [C1]
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2017 |
Willott JD, Murdoch TJ, Webber GB, Wanless EJ, 'Physicochemical behaviour of cationic polyelectrolyte brushes', PROGRESS IN POLYMER SCIENCE, 64 52-75 (2017) [C1]
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2017 |
McLean B, Eveleens CA, Mitchell I, Webber GB, Page AJ, 'Catalytic CVD synthesis of boron nitride and carbon nanomaterials - synergies between experiment and theory', PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 19 26466-26494 (2017) [C1]
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2017 |
Murdoch TJ, Humphreys BA, Willott JD, Prescott SW, Nelson A, Webber GB, Wanless EJ, 'Enhanced specific ion effects in ethylene glycol-based thermoresponsive polymer brushes', JOURNAL OF COLLOID AND INTERFACE SCIENCE, 490 869-878 (2017) [C1]
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2016 |
Jarrett E, Ireland PM, Webber GB, Wanless EJ, 'Particle-liquid structures formed by electric fields', Powder Technology, 297 1-7 (2016) [C1]
© 2016. We report the manufacture of complex structures of silica, coal or sphalerite particles around a water droplet, driven by an electrostatic field. A particle bed was deposi... [more]
© 2016. We report the manufacture of complex structures of silica, coal or sphalerite particles around a water droplet, driven by an electrostatic field. A particle bed was deposited on an electrically biased substrate and an earthed water drop brought close, such that the particles jumped to the drop. These structures' shape and internal composition were determined by a combination of the particles' wettability and electrical properties, and other attributes such as shape, size and density were also thought to play a role. Hydrophilic particles tend to be internalised by the drop, while hydrophobic ones tend to form a layer or shell on the surface. Thus, one example of these structures was a 'complex liquid marble', with a hydrophilic particle suspension core and a stabilising shell of hydrophobic particles.
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2016 |
Riazi H, Murphy T, Webber GB, Atkin R, Tehrani SSM, Taylor RA, 'Specific heat control of nanofluids: A critical review', International Journal of Thermal Sciences, 107 25-38 (2016) [C1]
© 2016 Elsevier Masson SAS. All rights reserved. Specific heat is a key thermal property in energy systems and is directly linked with heat storage and transfer. Concentrated sola... [more]
© 2016 Elsevier Masson SAS. All rights reserved. Specific heat is a key thermal property in energy systems and is directly linked with heat storage and transfer. Concentrated solar thermal (CST) power plants which incorporate thermal storage show promise to deliver affordable, renewable and reliable electricity without harmful emissions. As compared to wind and photovoltaic installations, which are intermittent, CST systems (with thermal storage) represent a technology which can be dispatched to provide a good match with energy demand - or at least to maximize revenue. At present, molten salts represent the dominant thermal storage medium. However, the low specific heat value of molten salts severely limits their applicability. Increasing the specific heat of molten salts could allow for a sizable reduction in storage volume, or for more energy to be stored in the same volume. Recently, researchers have shown that the specific heat of fluids can be altered through the addition of nanoparticles, although the fundamental governing mechanisms for the observed changes in this property have not yet been agreed upon. This paper provides a comprehensive review of recent, albeit sometimes contrary, nanofluid specific heat studies. Since a critical review of the ongoing work in this field has not yet been compiled, this paper provides insights into the range and magnitude of specific heat changes. This review also discusses possible underlying enhancement mechanisms, the impacts of colloidal stability, and uses these to rationalize the diverse range of results seen in the literature. Through reviewing the salient literature, it is hoped that this paper will help to guide future efforts in controlling the specific heat of nanosalts.
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2016 |
Cooper PK, Li H, Rutland MW, Webber GB, Atkin R, 'Tribotronic control of friction in oil-based lubricants with ionic liquid additives.', Phys Chem Chem Phys, 18 23657-23662 (2016) [C1]
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2016 |
Morse AJ, Giakoumatos EC, Tan SY, Webber GB, Armes SP, Ata S, Wanless EJ, 'Giant pH-responsive microgel colloidosomes: Preparation, interaction dynamics and stability', Soft Matter, 12 1477-1486 (2016) [C1]
© 2016 The Royal Society of Chemistry.The interactions of two oil droplets grown in the presence of swollen, lightly cross-linked cationic poly(tert-butylamino)ethyl methacrylate ... [more]
© 2016 The Royal Society of Chemistry.The interactions of two oil droplets grown in the presence of swollen, lightly cross-linked cationic poly(tert-butylamino)ethyl methacrylate (PTBAEMA) microgels was monitored using a high-speed video camera. Three oils (n-dodecane, isopropyl myristate and sunflower oil) were investigated, each in the absence and presence of an oil-soluble cross-linker [tolylene 2,4-diisocyanate-terminated poly(propylene glycol), PPG-TDI]. Adsorption of the swollen microgel particles was confirmed by interfacial tension, interfacial elasticity and dilational viscosity measurements on single pendant oil droplets, and assessment of the oscillatory dynamics for coalescing droplet pairs. Like the analogous bulk emulsions, particle adsorption alone did not prevent coalescence of pairs of giant Pickering emulsion droplets. However, prior addition of surface-active PPG-TDI cross-linker to the oil phase results in the formation of highly stable microgel colloidosomes via reaction with the secondary amine groups on the PTBAEMA chains. Colloidosome stability depended on the age of the oil-water interface. This reflects a balance between the adsorption kinetics of the PPG-TDI cross-linker and the microgel particles, each of which must be present at the interface to form a stable colloidosome. Colloidosome formation was virtually instantaneous in n-dodecane, but took up to 120 s in the case of isopropyl myristate. The impact of an acid-induced latex-to-microgel transition on the interaction of giant colloidosomes (originally prepared at pH 10 using isopropyl myristate) was also studied. This acid challenge did not result in coalescence, which is consistent with a closely-related study (A. J. Morse et al., Langmuir, 2014, 30(42), 12509-12519). No evidence was observed for inter-colloidosome cross-linking, which was attributed to retention of an aqueous film between the adjacent pair of colloidosomes.
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2016 |
Sweeney J, Webber GB, Atkin R, 'Poly(ethylene oxide) Mushrooms Adsorbed at Silica-Ionic Liquid Interfaces Reduce Friction', LANGMUIR, 32 1947-1954 (2016) [C1]
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2016 |
Ireland PM, Noda M, Jarrett ED, Fujii S, Nakamura Y, Wanless EJ, Webber GB, 'Electrostatic formation of liquid marbles - Influence of drop and particle size', Powder Technology, 303 55-58 (2016) [C1]
© 2016 We report the first study of the influence of drop and particle size on the electrostatic manufacture and subsequent stability of liquid marbles. It is clear from this stud... [more]
© 2016 We report the first study of the influence of drop and particle size on the electrostatic manufacture and subsequent stability of liquid marbles. It is clear from this study that the ¿rules¿ for electrostatic formation of liquid marbles are quite different for those for conventional direct-contact manufacture. Formation of liquid marbles was observed when an earthed water drop of volume 3¿7¿µL was brought into proximity with a bed of highly-charged polystyrene particles of diameter 22¿153¿µm. Under appropriate conditions the particles jumped to and coated the drop, producing a particle-liquid aggregate that dropped to the bed surface in the form of either a stable liquid marble or a particle-stabilised sessile drop. The subsequent evolution of the physical dimensions of the metastable aggregate was measured as the liquid drained into the bed, and its stability assessed. Formation of stable liquid marbles appeared to occur more easily for smaller drops and larger particles, and some of these considerably exceeded the conventionally-understood limit for the ratio of particle to drop size of stable liquid marbles.
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2016 |
Murdoch TJ, Willott JD, De Vos WM, Nelson A, Prescott SW, Wanless EJ, Webber GB, 'Influence of Anion Hydrophilicity on the Conformation of a Hydrophobic Weak Polyelectrolyte Brush', Macromolecules, 49 9605-9617 (2016) [C1]
© 2016 American Chemical Society. The conformation of a hydrophobic, weak cationic poly(2-diisopropylamino)ethyl methacrylate (PDPA) brush was studied using neutron reflectometry ... [more]
© 2016 American Chemical Society. The conformation of a hydrophobic, weak cationic poly(2-diisopropylamino)ethyl methacrylate (PDPA) brush was studied using neutron reflectometry as a function of aqueous solution pH, ionic strength, and anion identity. In pH 4, 10 mM potassium nitrate the brush is highly charged, resulting in an extended, dilute conformation; at pH 9 the uncharged brush collapses to a single, dense layer. The brush response to added salt at constant pH (4.5) for varying concentrations of the potassium salts of acetate, nitrate, and thiocyanate revealed ion-specific conformations of the brush. At low ionic strength (0.1 mM) the brush was collapsed, independent of salt identity, while at higher ionic strengths (up to 500 mM) the conformation was dependent on counterion identity. The brush exhibited extended conformations in the presence of kosmotropic acetate counterions, while collapsed conformations were retained in the presence of strongly chaotropic thiocyanate counterions. The brush showed a richer set of behaviors in the solutions containing the weakly chaotropic nitrate anion, being similar to acetate (swollen) at intermediate concentrations but similar to thiocyanate (collapsed) at high salt concentrations. Numerical self-consistent field (nSCF) simulations indicate that the response of the brush to pH changes is dominated by the hydrophobicity of the polymer at pH values near the pKa. Furthermore, the simulations reveal that the addition of a single Flory-Huggins interaction parameter analogous to the hydrophilicity of the counterion is sufficient to replicate the observed specific anion response of a hydrophobic weak polyelectrolyte brush.
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2016 |
Chen Z, McLean B, Ludwig M, Stefanovic R, Warr GG, Webber GB, et al., 'Nanostructure of Deep Eutectic Solvents at Graphite Electrode Interfaces as a Function of Potential', Journal of Physical Chemistry C, 120 2225-2233 (2016) [C1]
© 2016 American Chemical Society. Atomic force microscopy (AFM), density functional theory (DFT) calculations, and contact angle measurements have been used to investigate the liq... [more]
© 2016 American Chemical Society. Atomic force microscopy (AFM), density functional theory (DFT) calculations, and contact angle measurements have been used to investigate the liquid-highly ordered pyrolytic graphite (HOPG) electrode interface for three deep eutectic solvents (DESs) as a function of applied potential. The DESs examined are 1:2 mixtures of choline chloride and urea (ChCl:urea), choline chloride and ethylene glycol (ChCl:ethylene glycol), and choline chloride and glycerol (ChCl:glycerol). DFT calculations reveal that in all cases the molecular component is excluded from the graphite interface at all potentials, while chloride and choline are attracted into the Stern layer at positive and negative potentials, respectively. AFM force curves confirm these trends and also show that the first near surface liquid layer in contact with the Stern layer is rich in the molecular component. The extent of near surface layering increases with potential and the hydrogen bonding capacity of the molecular component. The variation in the macroscopic contact angle with potential is consistent with changes in the Stern layer composition.
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2016 |
Murdoch TJ, Humphreys BA, Willott JD, Gregory KP, Prescott SW, Nelson A, et al., 'Specific Anion Effects on the Internal Structure of a Poly(N-isopropylacrylamide) Brush', Macromolecules, 49 6050-6060 (2016) [C1]
© 2016 American Chemical Society. The effect of anion identity and temperature on the internal nanostructure of poly(N-isopropylacrylamide) brushes were investigated using neutron... [more]
© 2016 American Chemical Society. The effect of anion identity and temperature on the internal nanostructure of poly(N-isopropylacrylamide) brushes were investigated using neutron reflectometry (NR), atomic force microscopy (AFM), and quartz crystal microbalance with dissipation monitoring (QCM-D). NR and QCM-D measurements showed that addition of strongly kosmotropic acetate anions shifted the lower critical solution temperature (LCST) to lower temperatures relative to pure D2O/H2O, while strongly chaotropic thiocyanate anions shifted the LCST to higher temperatures. Polymer density profiles derived from NR showed direct evidence of vertical phase separation at temperatures around the LCST in all conditions. Results indicate that the density profiles were not simple modulations of structures observed in D2O to higher or lower temperatures, with both anion identity and ionic strength found to influence the qualitative features of the profiles. In particular, the presence of thiocyanate broadened the LCST transition which is attributed to the ability of the thiocyanate anion to electrosterically stabilize the brush above its LCST. Complementary AFM data showed that the acetate ion induced collapsed structures while a broader transition is observed in the presence of thiocyanate.
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2016 |
Willott JD, Murdoch TJ, Webber GB, Wanless EJ, 'Nature of the Specific Anion Response of a Hydrophobic Weak Polyelectrolyte Brush Revealed by AFM Force Measurements', Macromolecules, 49 2327-2338 (2016) [C1]
© 2016 American Chemical Society. Complementary interaction force measurements between an atomic force microscope (AFM) tip or colloid probe and a weak polybasic brush have been s... [more]
© 2016 American Chemical Society. Complementary interaction force measurements between an atomic force microscope (AFM) tip or colloid probe and a weak polybasic brush have been shown to yield a number of fundamental characteristics of the brush and its response to the presence of specific anions in aqueous solution. Stretching of the poly(2-diisopropylamino)ethyl methacrylate (PDPA) chains physisorbed to the AFM tip and modeling the resultant force curves allowed the persistence and contour lengths, molecular weight, and thus grafting density of the brush to be determined. In kosmotropic acetate, high osmotic forces associated with the swollen PDPA brush repelled the colloid probe during both approach and retraction. For mildly chaotropic nitrate the behavior was similar, but at high ionic strength and during retraction, the interaction was strongly adhesive partly because of decreased brush solvation. For strongly chaotropic thiocyanate, the interaction was adhesive over the entire concentration range studied. Here, physical contact between the poorly solvated brush and the colloid resulted in an attractive force.
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2016 |
Humphreys BA, Willott JD, Murdoch TJ, Webber GB, Wanless EJ, 'Specific ion modulated thermoresponse of poly(N-isopropylacrylamide) brushes', PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 18 6037-6046 (2016) [C1]
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2015 |
Willott JD, Humphreys BA, Murdoch TJ, Edmondson S, Webber GB, Wanless EJ, 'Hydrophobic effects within the dynamic pH-response of polybasic tertiary amine methacrylate brushes.', Phys Chem Chem Phys, 17 3880-3890 (2015) [C1]
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2015 |
Sweeney J, Webber GB, Atkin R, 'Near surface properties of mixtures of propylammonium nitrate with n-alkanols 2. Nanotribology and fluid dynamics', Physical Chemistry Chemical Physics, 17 26629-26637 (2015) [C1]
This journal is © the Owner Societies. Colloid probe friction force microscopy (FFM) has been used to study the lubricity of propylammonium nitrate (PAN) mixed with n-alkanols con... [more]
This journal is © the Owner Societies. Colloid probe friction force microscopy (FFM) has been used to study the lubricity of propylammonium nitrate (PAN) mixed with n-alkanols confined between sliding silica and mica surfaces. Mixtures of PAN with butanol, hexanol, octanol and dodecanol were investigated for various n-alkanol volume fractions to elucidate the effect of n-alkanol hydrocarbon chain length and concentration on shear forces. For all n-alkanols friction decreases with n-alkanol vol%. The trends in friction reduction with n-alkanol vol% do not correlate with changes in the bulk phase viscosity or the near surface nanostructure, and colloid probe atomic force microscope (AFM) fluid dynamic measurements showed that none of the mixtures shear thin. Thus, the reduction in friction is attributed to the n-alkanol disrupting solvophobic interactions between boundary layer propylammonium ions adsorbed to the mica and near surface liquid layers. The lowest friction is obtained for pure dodecanol, which is attributed to the dodecanol forming a robust boundary layer. Friction for the other pure n-alkanols is higher because the lateral attractions between adsorbed n-alkanols are too weak to facilitate the formation of a strong boundary layer, commensurate with the decreased hydrocarbon chain length.
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2015 |
McLean B, Li H, Stefanovic R, Wood RJ, Webber GB, Ueno K, et al., 'Nanostructure of [Li (G4)] TFSI and [Li (G4)] NO 3 solvate ionic liquids at HOPG and Au (111) electrode interfaces as a function of potential', Physical Chemistry Chemical Physics, 17 325-333 (2015) [C1]
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2015 |
Chen Z, Kobayashi Y, Webber GB, Ueno K, Watanabe M, Warr GG, Atkin R, 'Adsorption of Polyether Block Copolymers at Silica-Water and Silica-Ethylammonium Nitrate Interfaces.', Langmuir, 31 7025-7031 (2015) [C1]
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2015 |
Willott JD, Murdoch TJ, Humphreys BA, Edmondson S, Wanless EJ, Webber GB, 'Anion-specific effects on the behavior of pH-sensitive polybasic brushes.', Langmuir, 31 3707-3717 (2015) [C1]
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2014 |
Willott JD, Murdoch TJ, Humphreys BA, Edmondson S, Webber GB, Wanless EJ, 'Critical salt effects in the swelling behavior of a weak polybasic brush.', Langmuir, 30 1827-1836 (2014) [C1]
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2014 |
Sweeney J, Webber GB, Rutland MW, Atkin R, 'Effect of ion structure on nanoscale friction in protic ionic liquids.', Phys Chem Chem Phys, 16 16651-16658 (2014) [C1]
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2014 |
Morse AJ, Tan S-Y, Giakoumatos EC, Webber GB, Armes SP, Ata S, Wanless EJ, 'Arrested coalescence behaviour of giant Pickering droplets and colloidosomes stabilised by poly(tert-butylaminoethyl methacrylate) latexes.', Soft Matter, 10 5669-5681 (2014) [C1]
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2014 |
Smith JA, Webber GB, Warr GG, Zimmer A, Atkin R, Werzer O, 'Shear dependent viscosity of poly(ethylene oxide) in two protic ionic liquids', Journal of Colloid and Interface Science, 430 56-60 (2014) [C1]
Steady shear viscosity measurements have been performed on 100. kDa poly(ethylene oxide) (PEO) dissolved in the protic ionic liquids ethylammonium nitrate (EAN) and propylammonium... [more]
Steady shear viscosity measurements have been performed on 100. kDa poly(ethylene oxide) (PEO) dissolved in the protic ionic liquids ethylammonium nitrate (EAN) and propylammonium nitrate (PAN) and in water. The zero shear viscosity in all three solvents increases with polymer concentration, falling into three concentration regimes corresponding to dilute, semi-dilute and network solutions. Huggins plots reveal three distinct solvent conditions: good (water), good-theta (EAN) and theta (PAN). However, differences in the transition concentrations, power law behaviour of the viscosities, and relaxation times arising from shear thinning in the two ILs can be directly related to the effects of solvent nanostructure. © 2014 Elsevier Inc.
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2014 |
Liyanaarachchi KR, Webber GB, van Netten K, Moreno-Atanasio R, Galvin KP, 'Selective collection of fine particles by water drops', Advanced Powder Technology, (2014) [C1]
This study was concerned with the interaction between a gaseous dispersion of fine particles travelling in the horizontal direction and discrete drops of water falling vertically ... [more]
This study was concerned with the interaction between a gaseous dispersion of fine particles travelling in the horizontal direction and discrete drops of water falling vertically through the dispersion. A simple analytical model of the particle-drop collision was developed to describe the particle recovery by the drops as a function of the water flux, covering two extremes of relative velocity between the particles and drops. The Discrete Element Method was used to validate the analytical model. Further validation of the model and insights were obtained through experimental studies. The physical process of wetting was observed to be important in influencing the tendency of particles to become engulfed by the drops of water, or to either adhere to the drops or by-pass the drops altogether. Hydrophilic particles were readily engulfed while hydrophobic particles, at best, adhered to the surface of the drop, or failed to attach. Moreover, the recovery of the hydrophilic silica particles was significantly higher than the recovery of hydrophobic coal particles, with the selectivity ratio approximately 1.5. Spherical ballotini particles were the most sensitive, with a notable increase in recovery when cleaned, and evidence of increased recovery with increasing particle size. The recovery of irregular shaped silica flour particles, however, was largely independent of the particle size. A similar result was observed for irregular coal particles, though the recoveries were all lower than relatively more hydrophilic ballotini or silica flour. Crown Copyright © 2014.
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2014 |
Murphy T, Varela LM, Webber GB, Warr GG, Atkin R, 'Nanostructure-thermal conductivity relationships in protic ionic liquids', Journal of Physical Chemistry B, 118 12017-12024 (2014) [C1]
© 2014 American Chemical Society. The thermal conductivities of nine protic ionic liquids (ILs) have been investigated between 293 and 340 K. Within this range, the thermal conduc... [more]
© 2014 American Chemical Society. The thermal conductivities of nine protic ionic liquids (ILs) have been investigated between 293 and 340 K. Within this range, the thermal conductivities are between 0.18 and 0.30 W·m-1·K-1. These values are higher than those typically associated with oils and aprotic ILs, but lower than those of strongly hydrogen bonding solvents like water. Weak linear decreases in thermal conductivity with temperature are noted, with the exception of ethanolammonium nitrate (EtAN) where the thermal conductivity increases with temperature. The dependence of thermal conductivity on IL type is analyzed with use of the Bahe-Varela pseudolattice theory. This theory treats the bulk IL as an array of ordered domains with intervening domains of uncorrelated structure which enable and provide barriers to heat propagation (respectively) via allowed vibrational modes. For the protic ILs investigated, thermal conductivity depends strongly on the IL cation alkyl chain length. This is because the cation alkyl chain controls the dimensions of the IL bulk nanostructure, which consists of charged (ordered domains) and uncharged regions (disordered domains). As the cation alkyl chain controls the dimensions of the disordered domains, it thus limits the thermal conductivity. To test the generality of this interpretation, the thermal conductivities of propylammonium nitrate (PAN) and PAN-octanol mixtures were examined; water selectively swells the PAN charged domain, while octanol swells the uncharged regions. Up to a certain concentration, adding water increases thermal conduction and octanol decreases it, as expected. However, at high solute concentrations the IL nanostructure is broken. When additional solvent is added above this concentration the rate of change in thermal conductivity is greatly reduced. This is because, in the absence of nanostructure, the added solvent only serves to dilute the salt solution.
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2014 |
Addicoat MA, Stefanovic R, Webber GB, Atkin R, Page AJ, 'Assessment of the density functional tight binding method for protic ionic liquids', Journal of Chemical Theory and Computation, 10 4633-4643 (2014) [C1]
© 2014 American Chemical Society. Density functional tight binding (DFTB), which is ~100-1000 times faster than full density functional theory (DFT), has been used to simulate the... [more]
© 2014 American Chemical Society. Density functional tight binding (DFTB), which is ~100-1000 times faster than full density functional theory (DFT), has been used to simulate the structure and properties of protic ionic liquid (IL) ions, clusters of ions and the bulk liquid. Proton affinities for a wide range of IL cations and anions determined using DFTB generally reproduce G3B3 values to within 5-10 kcal/mol. The structures and thermodynamic stabilities of n-alkyl ammonium nitrate clusters (up to 450 quantum chemical atoms) predicted with DFTB are in excellent agreement with those determined using DFT. The IL bulk structure simulated using DFTB with periodic boundary conditions is in excellent agreement with published neutron diffraction data.
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2014 |
Smith JA, Webber GB, Warr GG, Zimmer A, Atkin R, Werzer O, 'Shear dependent viscosity of poly(ethylene oxide) in two protic ionic liquids', JOURNAL OF COLLOID AND INTERFACE SCIENCE, 430 56-60 (2014)
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2014 |
Smith J, Webber GB, Warr GG, Atkin R, 'Silica particle stability and settling in protic ionic liquids', Langmuir, 30 1506-1513 (2014) [C1]
Silica particle suspensions of 10 wt % have been investigated in the protic ionic liquids (ILs) ethylammonium nitrate (EAN), ethanolammonium nitrate (EtAN), propylammonium nitrate... [more]
Silica particle suspensions of 10 wt % have been investigated in the protic ionic liquids (ILs) ethylammonium nitrate (EAN), ethanolammonium nitrate (EtAN), propylammonium nitrate (PAN), and dimethylethylammonium formate (DMEAF). Static and dynamic light scattering reveal that single particles coexist in dynamic equilibrium with flocculated networks at room temperature. These types of systems are classified as weakly flocculated and are quite rare. As weakly flocculated systems generally exist only within a narrow range of conditions, the effect of temperature was probed. When temperature is increased, the thermal motion of suspended particles increases, favoring dispersion, but in ILs suspensions, heating reduces the stabilizing effect of the interfacial structure of the IL. When subjected to a small increase in temperature, particle suspensions in ILs become unstable, indicated by the absence of a peak corresponding to single particles in the light scattering data. For EAN and DMEAF, further increasing temperatures above 40 C returns the systems to a weakly flocculated state in which thermal energy is sufficient to break particles away from aggregates. Weakly flocculated suspensions in EAN and EtAN settle more rapidly than predicted by the Stokes equation, as the particles spend a significant portion of time in large, rapidly settling flocs. Surprisingly, suspensions in PAN and DMEAF settle slower than predicted. Oscillatory rheology indicates that these suspensions are viscoelastic, due to a persistent, long-range structure in the suspension that slows settling. In aggregated systems, settling is very rapid. © 2014 American Chemical Society.
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2013 |
Liyanaarachchi KR, Ireland PM, Webber GB, Galvin KP, 'Electrostatic formation of liquid marbles and agglomerates', APPLIED PHYSICS LETTERS, 103 (2013) [C1]
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2013 |
Cheesman BT, Neilson AJG, Willott JD, Webber GB, Edmondson S, Wanless EJ, 'Effect of Colloidal Substrate Curvature on pH-Responsive Polyelectrolyte Brush Growth', LANGMUIR, 29 6131-6140 (2013) [C1]
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2013 |
Elbourne A, Sweeney J, Webber GB, Wanless EJ, Warr GG, Rutland MW, Atkin R, 'Adsorbed and near-surface structure of ionic liquids determines nanoscale friction', CHEMICAL COMMUNICATIONS, 49 6797-6799 (2013) [C1]
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2013 |
Cheesman BT, Smith EG, Murdoch TJ, Guibert C, Webber GB, Edmondson S, Wanless EJ, 'Polyelectrolyte brush pH-response at the silica-aqueous solution interface: a kinetic and equilibrium investigation', PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 15 14502-14510 (2013) [C1]
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2013 |
Smith JA, Webber GB, Warr GG, Atkin R, 'Rheology of Protic Ionic Liquids and Their Mixtures', JOURNAL OF PHYSICAL CHEMISTRY B, 117 13930-13935 (2013) [C1]
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2012 |
Wakeham D, Eschebach DS, Webber GB, Atkin R, Warr GG, 'Surface composition of mixtures of ethylammonium nitrate, ethanolammonium nitrate, and water', Australian Journal of Chemistry, 65 1554-1556 (2012) [C1]
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2012 |
Carstens T, Hayes RL, Abedin SZE, Corr BJ, Webber GB, Borisenko N, et al., 'In situ STM, AFM and DTS study of the interface 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate/Au(1 1 1)', Electrochimica Acta, 82 48-59 (2012) [C1]
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2012 |
Sweeney JT, Hausen F, Hayes RL, Webber GB, Endres F, Rutland MW, et al., 'Control of nanoscale friction on gold in an ionic liquid by a potential-dependent ionic lubricant layer', Physical Review Letters, 109 155502 (2012) [C1]
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2012 |
Thompson KL, Giakoumatos EC, Ata S, Webber GB, Armes SP, Wanless EJ, 'Direct observation of giant pickering emulsion and colloidosome droplet interaction and stability', Langmuir, 28 16501-16511 (2012) [C1]
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2012 |
MacPherson SA, Webber GB, Moreno-Atanasio R, 'Aggregation of nanoparticles in high ionic strength suspensions: Effect of Hamaker constant and particle concentration', Advanced Powder Technology, 23 478-484 (2012) [C1]
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2012 |
Hayes RL, Borisenko N, Corr BJ, Webber GB, Endres F, Atkin R, 'Effect of dissolved LiCl on the ionic liquid-Au(111) electrical double layer structure', Chemical Communications, 48 10246-10248 (2012) [C1]
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2012 |
Cheesman BT, Willott JD, Webber GB, Edmondson S, Wanless EJ, 'pH-responsive brush-modified silica hybrids synthesized by surface-initiated ARGET ATRP', ACS Macro Letters, 1 1161-1165 (2012) [C1]
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2010 |
Smith JA, Werzer O, Webber GB, Warr GG, Atkin R, 'Surprising particle stability and rapid sedimentation rates in an ionic liquid', Journal of Physical Chemistry Letters, 1 64-68 (2010) [C1]
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2010 |
Dagastine RR, Webber GB, Manica R, Stevens GW, Grieser F, Chan DYC, 'Viscosity Effects on Hydrodynamic Drainage Force Measurements Involving Deformable Bodies', LANGMUIR, 26 11921-11927 (2010) [C1]
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2008 |
Webber GB, Edwards SA, Stevens GW, Grieser F, Dagastine RR, Chan DYC, 'Measurements of dynamic forces between drops with the AFM: novel considerations in comparisons between experiments and theory.', Soft Matter, 4 1270-1278 (2008) [C1]
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2008 |
Webber GB, Manica R, Edwards SA, Carnie SL, Stevens GW, Grieser F, et al., 'Dynamic Forces between a Moving Particle and a Deformable Drop.', The Journal of Physical Chemistry Part C: Nanomaterials and Interfaces, 112 567-574 (2008) [C1]
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2008 |
Sakai K, Webber GB, Vo C-D, Wanless EJ, Vamvakaki M, Butun V, et al., 'Characterization of layer-by-layer self-assembled multilayer films of diblock copolymer micelles', Langmuir, 24 116-123 (2008) [C1]
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2008 |
Webber GB, Stevens GW, Grieser F, Dagastine RR, Chan DYC, 'Variations in properties of atomic force microscope cantilevers fashioned from the same wafer.', Nanotechnology, 19 1-6 (2008) [C1]
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2007 |
Biggs S, Labarre M, Hodges C, Walker LM, Webber GB, 'Polymerized rodlike micelle adsorption at the solid-liquid interface', LANGMUIR, 23 8094-8102 (2007) [C1]
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2007 |
Biggs S, Sakai K, Addison T, Schmid A, Armes SP, Vamvakaki M, et al., 'Layer-by-layer formation of smart particle coatings using oppositely charged block copolymer micelles', ADVANCED MATERIALS, 19 247-+ (2007) [C1]
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2007 |
Smith EG, Webber GB, Sakai K, Biggs S, Armes SP, Wanless EJ, 'Direct visualization of a self-organized multilayer film of low T g diblock copolymer micelles', Journal of Physical Chemistry B, 111 5536-5541 (2007) [C1]
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2007 |
Sakai K, Smith EG, Webber GB, Baker MJ, Wanless EJ, Butun V, et al., 'pH-responsive behavior of selectively quaternized diblock copolymers adsorbed at the silica/aqueous solution interface', Journal of Colloid and Interface Science, 314 381-388 (2007) [C1]
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2006 |
Sakai K, Smith EG, Webber GB, Wanless EJ, Butun V, Armes SP, Biggs S, 'Effects of copolymer concentration and chain length on the pH-responsive behavior of diblock copolymer micellar films', Journal of Colloid and Interface Science, 303 372-379 (2006) [C1]
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2006 |
Sakai K, Smith EG, Webber GB, Baker MJ, Wanless EJ, Butun V, et al., 'Characterizing the pH-responsive behavior of thin films of diblock copolymer micelles at the silica/aqueous solution interface', Langmuir, 22 8435-8442 (2006) [C1]
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2006 |
Sakai K, Smith EG, Webber GB, Schatz C, Wanless EJ, Butun V, et al., 'pH-responsive diblock copolymer micelles at the silica/aqueous solution interface: Adsorption kinetics and equilibrium studies', Journal of Physical Chemistry B, 110 14744-14753 (2006) [C1]
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2006 |
Sakai K, Smith EG, Webber GB, Schatz C, Wanless EJ, Butun V, et al., 'Comparison of the adsorption of cationic diblock copolymer micelles from aqueous solution onto mica and silica', Langmuir, 22 5328-5333 (2006) [C1]
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2005 |
Webber GB, Wanless EJ, Armes SP, Biggs S, 'Tunable diblock copolymer micelles-adapting behaviour via subtle chemical modifications', FARADAY DISCUSSIONS, 128 193-209 (2005) [C1]
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2004 |
Webber GB, Wanless EJ, Armes SP, Tang Y, Li Y, Biggs S, 'Nano-Anemones: Stimulus-Responsive Copolymer-Micelle Surfaces', Advanced Materials, 16 1794-1798 (2004) [C1]
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2002 |
Webber GB, Wanless EJ, Butun V, Armes S, Biggs SR, 'Self-organized monolayer films of stimulus-responsive micelles', Nano Letters, 2 1307-1313 (2002) [C1]
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2001 |
Webber GB, Wanless EJ, Armes SP, Baines FL, Biggs S, 'Adsorption of amphiphilic diblock copolymer micelles at the mica/solution interface', Langmuir, 17 5551-5561 (2001) [C1]
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Lobel BT, Fujiwara J, Fujii S, Thomas CA, Ireland PM, Wanless EJ, Webber GB, 'Formation of liquid marbles & aggregates: rolling and electrostatic formation using conductive hexagonal plates', Materials Advances, 1 3302-3313
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