ORCID Profile
0000-0003-0869-4396
Current Organisations
Australian National University
,
The University of Newcastle
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Physical Chemistry (Incl. Structural) | Colloid and Surface Chemistry | Colloid And Surface Chemistry | Powder and Particle Technology | Physical Chemistry Of Macromolecules | Condensed Matter Physics | Mineral Processing/Beneficiation | Nanotechnology | Condensed Matter Physics—Electronic And Magnetic Properties; | Condensed Matter Physics—Structural Properties | Colloid and surface chemistry | Nanotechnology | Quantum Chemistry | Process Control and Simulation | Nanochemistry and Supramolecular Chemistry | Membrane and Separation Technologies | Polymers | Alloy Materials | Structural Biology (incl. Macromolecular Modelling) | Physical chemistry | Functional Materials | Hydrometallurgy | Resources Engineering and Extractive Metallurgy | Cellular Interactions (Incl. Adhesion, Matrix, Cell Wall) | Materials Engineering | Mineral Processing | Petroleum and Reservoir Engineering | Computational chemistry | Catalysis and Mechanisms of Reactions | Macromolecular and Materials Chemistry | Chemical Thermodynamics and Energetics | Chemical Engineering Not Elsewhere Classified | Transport Properties and Non-Equilibrium Processes | Structural Chemistry and Spectroscopy | Nanoscale Characterisation | Nanomaterials | Diagnostic Applications | Surfaces and Structural Properties of Condensed Matter | Soft Condensed Matter | Electronic and Magnetic Properties of Condensed Matter; Superconductivity | Molecular and Organic Electronics | Condensed Matter Imaging | Condensed Matter Characterisation Technique Development
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Chemical Sciences | Chemical sciences | Expanding Knowledge in the Physical Sciences | Expanding Knowledge in Engineering | Physical sciences | Concentrating processes of other base metal ores | Treatments (e.g. chemicals, antibiotics) | Soaps and cosmetics | Polymeric materials (e.g. paints) | Concentrating Processes of Base Metal Ores (excl. Aluminium and Iron Ores) | Field crops | Solar-photoelectric | First Stage Treatment of Ores and Minerals not elsewhere classified | Oil and Gas Extraction | Ceramics, glass and industrial mineral products not elsewhere classified | Transformation of Coal into Gaseous Fuels | Energy Storage (excl. Hydrogen) | Coal Mining and Extraction | Integrated Circuits and Devices | Mining and Extraction of Aluminium Ores | Polymeric Materials (e.g. Paints) | Transformation of Gas into Liquid Fuels | Transformation of Coal into Liquid Fuels | Processed food products and beverages not elsewhere classified | Integrated circuits and devices | Primary mining and extraction processes | Energy transformation not elsewhere classified | Oil and Gas Refining | "Stone, ceramics and clay materials" | Industrial Chemicals and Related Products not elsewhere classified | Human Pharmaceutical Products not elsewhere classified | Precious (Noble) Metal Ore Exploration | Beneficiation or Dressing of Iron Ores | Expanding Knowledge in the Biological Sciences | Diamond Exploration |
Related Links
Publications
Electrostatic Adsorption Behaviors of Polymer Plates to a Droplet
Publisher: American Chemical Society (ACS)
Date: 03-07-2023
Slow organization of cationic surfactant adsorbed to silica from solutions far below the CMC
Publisher: American Chemical Society (ACS)
Date: 08-09-2001
DOI: 10.1021/JP011503+
Direct Visualization of a Self-Organized Multilayer Film of Low Tg Diblock Copolymer Micelles
Publisher: American Chemical Society (ACS)
Date: 05-2007
DOI: 10.1021/JP072231Z
Abstract: The first in situ proof of the presence of true nanoscale micelle structure within alternating layers of a self-assembled cationic and anionic diblock copolymer micelle-micelle multilayer film is presented using atomic force microscopy. Apparently similar layer morphologies are distinguished by the interaction force curves normal to each layer. The three-dimensional order in these low Tg diblock copolymer films, together with their mechanical resilience and strongly hydrated nature, suggests many new technological applications.
Electrostatic Formation of Liquid Marbles Using Thermo-responsive Polymer-coated Particles
Publisher: The Chemical Society of Japan
Date: 05-06-2019
DOI: 10.1246/CL.190105
pH-Responsive Particle-Liquid Aggregates—Electrostatic Formation Kinetics
Publisher: Frontiers Media SA
Date: 14-06-2018
The direction of influence of specific ion effects on a pH and temperature responsive copolymer brush is dependent on polymer charge
Publisher: Elsevier BV
Date: 02-2021
Ultra-high molecular weight linear coordination polymers with terpyridine ligands
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9SC01115C
Abstract: This first report of ultra-high molecular weight ( kDa) linear coordination polymers demonstrates their use in agricultural spray drift control.
Imaging Delicate Coatings under Water using Atomic Force Microscopy
Publisher: Royal Microscopical Society
Date: 06-12-2009
Enrichment of Charged Monomers Explains Non-monotonic Polymer Volume Fraction Profiles of Multi-stimulus Responsive Copolymer Brushes
Publisher: American Chemical Society (ACS)
Date: 14-10-2020
The formation of polyethyleneimine–trimethoxymethylsilane organic–inorganic hybrid particles
Publisher: Elsevier BV
Date: 08-2013
Effect of Colloidal Substrate Curvature on pH-Responsive Polyelectrolyte Brush Growth
Publisher: American Chemical Society (ACS)
Date: 07-05-2013
DOI: 10.1021/LA4004092
Abstract: Coatings consisting of polymer brushes are an effective way to modify solid interfaces. Polymer brush-modified hybrid particles have been prepared by surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (SI-ARGET ATRP) of 2-(diethylamino)ethyl methacrylate (DEA) on silica particles. We have optimized the synthesis with respect to changing the reducing agent, temperature, and reaction solvent from an aqueous ethanol mixture to an aqueous methanol mixture. Our flexible electrostatically adsorbed macroinitiator approach allows for the modification of a variety of surfaces. Polybasic brushes have been grown on silica particles of different sizes, from 120 to 840 nm in diameter, as well as on wafers, and a comparison of the products has allowed the effect of surface curvature to be elucidated. An examination of the thickness of the dry brush and the aqueous hydrodynamic brush at both pH 7 and at 4 demonstrated that growth increased substantially with substrate curvature for particles with a diameter below 450 nm. This is attributed to the increasing separation between active chain ends, reducing the rate of termination. This is believed to be the first time that this effect has been demonstrated experimentally. Furthermore, we have seen that polymer brush growth on planar wafers was significantly reduced when the reaction mixture was stirred.
Surface-Aggregate Shape Transformation
Publisher: American Chemical Society (ACS)
Date: 1996
DOI: 10.1021/LA9605448
Effect of alcohol frothing agents on the coalescence of bubbles coated with hydrophobized silica particles
Publisher: Elsevier BV
Date: 07-2015
Surfactant Boundary Lubricant Film Modified by an Amphiphilic Diblock Copolymer
Publisher: American Chemical Society (ACS)
Date: 03-2005
DOI: 10.1021/LA047878E
Abstract: The effect of the uptake of a low-molecular-weight hiphilic diblock copolymer on the morphology of didodecyldimethylammonium bromide (DDAB) adsorbed layers on mica, the interactions between two coated surfaces, and the frictional properties of the boundary film have been studied using an atomic force microscope and a dynamic surface forces apparatus nanotribometer. When DDAB-coated surfaces in aqueous solution were compressed, hemifusion or removal of the adsorbed surfactant bilayers could not be induced, and no frictional force could be measured between the surfaces, which display superior lateral cohesion and lubricant properties. Coadsorbing octadecyl end modified poly(ethylene oxide) chains at low density facilitates hemifusion, generating significant shear stress and leading to stick-slip instabilities. The mixed films regain their lateral cohesion at higher adsorbed copolymer densities, but an extra short-range attraction brings the adsorbed layers into adhesive contact without causing bilayer hemifusion. Here, noticeable frictional forces are also measured.
Adsorption characteristics of zwitterionic diblock copolymers at the silica/aqueous solution interface
Publisher: Elsevier BV
Date: 2008
DOI: 10.1016/J.JCIS.2007.09.072
Abstract: The adsorption of a zwitterionic diblock copolymer, poly(2-(diethylamino)ethyl methacrylate)-block-poly(methacrylic acid) (PDEA59-PMAA50), at the silica/aqueous solution interface has been characterised as a function of pH. In acidic solution, this copolymer forms core-shell micelles with the neutral PMAA chains being located in the hydrophobic cores and the protonated PDEA chains forming the cationic micelle coronas. In alkaline solution, the copolymer forms the analogous inverted micelles with anionic PMAA coronas and hydrophobic PDEA cores. The morphology of the adsorbed layer was observed in situ using soft-contact atomic force microscopy (AFM): this technique suggests the formation of a thin adsorbed layer at pH 4 due to the adsorption of in idual copolymer chains (unimers) rather than micelle aggregates. This is supported by the remarkably low dissipation values and the relatively low degrees of hydration for the adsorbed layers, as estimated using a combination of quartz crystal microbalance with dissipation monitoring (QCM-D) and optical reflectometry (OR). In alkaline solution, analysis of the adsorption data suggests a conformation for the adsorbed copolymers where one block projects normal to the solid/liquid interface this layer consists of a hydrophobic PDEA anchor block adsorbed on the silica surface and an anionic PMAA buoy block extending into the solution phase. Tapping mode AFM studies were also carried out on the silica surfaces after removal from the copolymer solutions and subsequent drying. Interestingly, in these cases micelle-like surface aggregates were observed from both acidic and alkaline solutions. The lateral dimension of the aggregates seen is consistent with the corresponding hydrodynamic diameter of the copolymer micelles in bulk solution. The combination of the in situ and ex situ AFM data provides evidence that, for this copolymer, micelle aggregates are only seen in the ex situ dry state as a result of the substrate withdrawal and drying process. It remains unclear whether these aggregates are caused by micelle deposition at the surface during the substrate withdrawal from the solution or as a result of unimer rearrangements at the drying front as the liquid recedes from the surface.
Determination of contact angles of nanosized silica particles by multi-angle single-wavelength ellipsometry
Publisher: CSIRO Publishing
Date: 2007
DOI: 10.1071/CH07133
Abstract: The determination of nanoparticle wettability is an area of great practical importance to materials science and engineering fields. There has been some recent interest in using spectroscopic analysis to indirectly categorize behaviour of monolayers, using the reflective and refractive properties of immersed particles. A method is developed here to calculate specific contact information for nanoparticles at an air–water interface, using single wavelength ellipsometry. A two-layer model is used that considers the refractive index of the immersed and non-immersed particle portions. Pressureâarea isotherms and Brewster angle images were used to confirm and categorize the nature of a packed monolayer, and ψ and Δ measurements taken of the interface. Immersion thickness was calculated and related to an equilibrium contact angle, and combined thickness data for the two layers was successfully related to the diameter of the particles.
Influence of molecular weight on PNIPAM brush modified colloidal silica particles
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C8SM01824C
Abstract: The internal structure of PNIPAM brush modified silica particles has been probed as a function of temperature and molecular weight.
Direct Observation of Individual Particle Armored Bubble Interaction, Stability, and Coalescence Dynamics
Publisher: American Chemical Society (ACS)
Date: 03-07-2013
DOI: 10.1021/JP402052F
Abstract: The interactions between two in idual particle-stabilized bubbles were investigated, in the absence of surfactant, using a combination of coalescence rig and high-speed video camera. This combination allows the visualization of bubble coalescence dynamics which provide information on bubble stability. Experimental data suggested that bubble stability is enhanced by both the adsorption of particles at the interface as indicated by the long induction time and the increase in d ing coefficient at high surface coverage. The interaction between an armored bubble and a bare bubble (asymmetric interaction) can be destabilized through the addition of a small amount of salt, which suggested that electrostatic interactions play a significant role in bubble stability. Interestingly, the DLVO theory cannot be used to describe the bubble stability in the case of a symmetric interaction as coalescence was inhibited at 0.1 M KCl in both the absence and presence of particles at the interfaces. Furthermore, bubbles can also be destabilized by increasing the particle hydrophobicity. This behavior is due to thinner liquid films between bubbles and an increase in film drainage rate. The fraction of particles detached from the bubble surface after film rupture was found to be very similar within the range of solution ionic strength, surface coverage, and particle hydrophobicity studied. This lack of dependence implies that the kinetic energy generated by the coalescing bubbles is larger than the attachment energy of the particles and dominates the detachment process. This study illuminates the stability behavior of in idual particle-stabilized bubbles and has potential impact on processes which involve their interaction.
Interaction of a spherical particle with a neutrally buoyant immiscible droplet in salt solution
Publisher: Elsevier BV
Date: 11-2017
Arrested coalescence behaviour of giant Pickering droplets and colloidosomes stabilised by poly(tert-butylaminoethyl methacrylate) latexes
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4SM00801D
Abstract: Coalescence of latex particle covered oil droplets is controlled by the presence of oil-soluble cross-linker in one or both droplets.
Giant Pickering Droplets: Effect of Nanoparticle Size and Morphology on Stability
Publisher: American Chemical Society (ACS)
Date: 26-07-2017
DOI: 10.1021/ACS.LANGMUIR.7B01383
Abstract: The interaction between a pair of millimeter-sized nanoparticle-stabilized n-dodecane droplets was analyzed using a high-speed video camera. The droplets were grown in the presence of either poly(glycerol monomethacrylate)-poly(benzyl methacrylate) (PGMA-PBzMA) diblock copolymer spheres or poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate)-poly(benzyl methacrylate) (PGMA-PHPMA-PBzMA) triblock copolymer worms prepared by polymerization-induced self-assembly. The effect of nanoparticle morphology on droplet coalescence was analyzed by comparing 22 nm spheres to highly anisotropic worms with a mean worm width of 26 nm and comparable particle contact angle. Both morphologies lowered the interfacial tension, providing direct evidence for nanoparticle adsorption at the oil-water interface. At 0.03 w/v % copolymer, an aging time of at least 90 s was required to stabilize the n-dodecane droplets in the presence of the worms, whereas no aging was required to produce stable droplets when using the spheres, suggesting faster diffusion of the latter to the surface of the oil droplets. The enhanced stability of the sphere-coated droplets is consistent with the higher capillary pressure in this system as the planar interfaces approach. However, the more strongly adsorbing worms ultimately also confer stability. At lower copolymer concentrations (≤0.01 w/v %), worm adsorption promoted droplet stability, whereas the spheres were unable to stabilize droplets even after longer aging times. The effect of mean sphere diameter on droplet stability was also assessed while maintaining an approximately constant particle contact angle. Small spheres of either 22 or 41 nm stabilized n-dodecane droplets, whereas larger spheres of either 60 or 91 nm were unable to prevent coalescence when the two droplets were brought into contact. These observations are consistent with the greater capillary pressure stabilizing the oil-water interfaces coated with the smaller spheres. Addition of an oil-soluble polymeric diisocyanate cross-linker to either the 60 or the 91 nm spheres produced highly stable colloidosomes, thus confirming adsorption of these nanoparticles.
Enhanced specific ion effects in ethylene glycol-based thermoresponsive polymer brushes
Publisher: Elsevier BV
Date: 03-2017
DOI: 10.1016/J.JCIS.2016.11.044
Abstract: The thermoresponse of poly(di(ethyleneglycol) methyl ether methacrylate) (PMEO
Characterization of Layer-by-Layer Self-Assembled Multilayer Films of Diblock Copolymer Micelles
Publisher: American Chemical Society (ACS)
Date: 04-12-2007
DOI: 10.1021/LA7021006
Abstract: The in situ layer-by-layer (LbL) self-assembly of low Tg diblock copolymer micelles onto a flat silica substrate is reported. The copolymers used here were a cationic poly(2-(dimethylamino)ethyl methacrylate)-block-poly(2-(diethylamino)ethyl methacrylate) (50qPDMA-PDEA 50q refers to a mean degree of quaternization of 50 mol % for the PDMA block) and zwitterionic poly(methacrylic acid)-block-poly(2-(diethylamino)ethyl methacrylate) (PMAA-PDEA), which has anionic character at pH 9. Alternate deposition of micelles formed by these two copolymers onto a silica substrate at pH 9 was examined. The in situ LbL buildup of the copolymer micelle films was monitored using zeta potential measurements, optical reflectometry, and a quartz crystal microbalance with dissipation monitoring (QCM-D). For a six layer deposition, complete charge reversal was observed after the addition of each layer. The OR data indicated clearly an increase in adsorbed mass with each additional micelle layer and suggest that some interdiffusion of copolymer chains between layers and/or an increase in the film roughness, and hence in the effective surface area of the micellar multilayers, must take place as the film is built up. QCM-D data indicated that the self-assembled micellar multilayers on a flat silica substrate undergo structural changes over a prolonged period. This is attributed to longer-term interdiffusion of the copolymer chains between the outer two layers after the initial adsorption of each layer is complete. The QCM-D data further suggest that the outer adsorbed layers adopt a progressively more extended conformation, particularly for the higher numbered layers. The morphology of each successive layer was characterized using in situ soft-contact atomic force microscopy, and micelle-like surface aggregates are clearly observed within each layer of the complex film, suggesting the persistence of aggregate structures throughout the multilayer structure.
Reversible pH-Triggered Encapsulation and Release of Pyrene by Adsorbed Block Copolymer Micelles
Publisher: American Chemical Society (ACS)
Date: 12-07-2008
DOI: 10.1021/LA801127R
Abstract: The well-established ability of copolymer micelles to encapsulate and release hydrophobic molecules has been investigated following their adsorption onto silica particles. Here, a pH-responsive copolymer, poly(2-(dimethylamino)ethyl methacrylate)- b-poly(2-(diethylamino)ethyl methacrylate) (PDMA(106)- b-PDEA(25)), has been used to study the formation and dissociation of adsorbed micelles through pH variation. This copolymer behaves as free unimers in aqueous solutions below pH 8 and forms micelles 29 nm in hydrodynamic diameter above this pH. Encapsulation and release of a model hydrophobic compound (pyrene) by in situ adjustment of the solution pH has been compared for both free and adsorbed micelles using fluorescence spectrophotometry, epifluorescence microscopy, and zeta potential measurements. At basic pH values, pyrene is solubilized within the cores of micelles adsorbed on silica particles: addition of acid leads to micelle dissociation and release of the pyrene into the bulk aqueous solution. Micelle adsorption does not appear to hinder the extent of pyrene uptake/release. Moreover, this pH-responsive behavior is both reversible and reproducible over multiple pH cycles.
Swelling and collapse of an adsorbed pH-responsive film-forming microgel measured by optical reflectometry and QCM
Publisher: American Chemical Society (ACS)
Date: 26-08-2010
DOI: 10.1021/LA1023218
Abstract: The swelling and deswelling of a pH-responsive electrosterically stabilized poly[2-(diethylamino)ethyl methacrylate] microgel adsorbed to silica surfaces have been quantified using the techniques of optical reflectometry (OR) and quartz crystal microbalance (QCM). It is shown that by utilizing and comparing OR measurements performed on wafers with differing oxide layer thicknesses the adsorbed amount and film thickness of the adsorbed microgel in both the swollen and deswollen forms can be determined. Also, the kinetics of the transition can be followed, revealing that collapse is a slower process than swelling, and direct support is provided for the formation of a dense outer layer or skin during collapse that slows the deswelling process. It is shown that the adsorption of this low glass transition temperature film-forming microgel latex is robust to changes in pH after an initial swelling event which is responsible for desorption of a large and variable fraction of the initially adsorbed polymer. Subsequent deswelling and swelling of the adsorbed film indicates that adsorption to a surface greatly hinders the volumetric swelling capacity of the microgel film. In its swollen state the film is only 3-4 times thicker than the collapsed film, whereas for particles in bulk the volume increases by a factor of 20 upon protonation of the tertiary amine residues. QCM results show that even in the collapsed form the film contains a considerable amount of water. Further, the viscoelasticity of the deswollen film is similar to that of the swollen film, suggesting that the degree of cross-linking is the primary determinant of viscoelasticity.
Adsorbed and near surface structure of ionic liquids at a solid interface
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3CP44163F
Abstract: The structure of solid-ionic liquid (IL) interfaces has been characterised with unprecedented clarity by employing a range of atomic force microscopy (AFM) imaging techniques and tip pressures appropriate for the system under study. Soft contact and litude-modulation (AM) AFM imaging have been used to elucidate the lateral structure of ILs adsorbed onto mica, and in the near surface ion layers. Data is presented for ethylammonium nitrate (EAN) and 1-ethyl-3-methylimidazolium bis(trifluoro-methylsulfonyl)imide (EMIm TFSI). Whereas EAN is a protic IL that forms a nanostructured sponge phase in the bulk, EMIm TFSI is aprotic and has weak (or absent) bulk association structure. Comparison of results obtained for the two liquids elucidates how the strength of bulk liquid morphology effects lateral organisation at the surface, and any effect of IL class, i.e. protic versus aprotic. Imaging reveals EAN self assembles at the solid surface in a worm-like morphology, whereas EMIm cations adsorb in a more isolated fashion, but still in rows templated by the mica surface. To the authors' knowledge, the wormlike structures present at the EAN-mica interface are the smallest self-assembled aggregates ever imaged on a solid surface.
Formation of liquid marbles & aggregates: rolling and electrostatic formation using conductive hexagonal plates
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0MA00670J
Abstract: A conductive coating is added to PET plates using a novel synthetic method and liquid marble manufactured using electrostatics forces.
Counterion Effects on Hexadecyltrimethylammonium Surfactant Adsorption and Self-Assembly on Silica
Publisher: American Chemical Society (ACS)
Date: 16-05-2014
DOI: 10.1021/LA9910935
The roles of particles in multiphase processes: Particles on bubble surfaces
Publisher: Elsevier BV
Date: 11-2015
DOI: 10.1016/J.CIS.2015.08.008
Abstract: Particle-stabilised foams (or froths) form the fundamental framework of industrial processes like froth flotation. This review provides an overview of the effects of particles on bubble surfaces. The characteristics of the particles have a profound effect on the stability of the bubbles although the stabilisation mechanisms may differ. It is well known that layers of particles may provide a steric barrier between two interfaces, which prevents the coalescence of bubbles. Although perhaps considered of lesser importance, it is interesting to note that particles may affect the bubble surface and momentarily suppress coalescence despite being absent from the film separating two bubbles. Foams are at best metastable and coalescence occurs to achieve a state of minimum energy. Despite this, particles have been reported to stabilise bubbles for significant periods of time. Bubble coalescence is accompanied by a release of energy triggered by the sudden change in surface area. This produces a distinctive oscillation of the bubble surface, which may be influenced by the presence of incompressible particles yielding unique surface properties. A survey of the literature shows that the properties of these composite materials are greatly affected by the physicochemical characteristics of the particles such as hydrophobicity and size. The intense energy released during the coalescence of bubbles may be sufficient to expel particles from the bubble surface. It is noted that the detachment of particles may preferentially occur from specific locations on the bubble surface. Examination of the research accounts again reveals that the properties of the particles may affect their detachment upon the oscillation of the bubble surface. However, it is believed that most parameters affecting the detachment of particles are in fact modifying the dynamics of the three-phase line of contact. Both the oscillation of a coalescing bubble and the resulting detachment of particles are highly dynamic processes. They would greatly benefit from computer simulation studies.
The influence of chain length and electrolyte on the adsorption kinetics of cationic surfactants at the silica–aqueous solution interface
Publisher: Elsevier BV
Date: 10-2003
DOI: 10.1016/S0021-9797(03)00631-3
Abstract: The equilibrium and kinetic aspects of the adsorption of alkyltrimethylammonium surfactants at the silica-aqueous solution interface have been investigated using optical reflectometry. The effect of added electrolyte, the length of the hydrocarbon chain, and of the counter- and co-ions has been elucidated. Increasing the length of the surfactant hydrocarbon chain results in the adsorption isotherm being displaced to lower concentrations. The adsorption kinetics indicate that above the cmc micelles are adsorbing directly to the surface and that as the chain length increases the hydrophobicity of the surfactant has a greater influence on the adsoption kinetics. While the addition of 10 mM KBr increases the CTAB maximal surface excess, there is no corresponding increase for the addition of 10 mM KCl to the CTAC system. This is attributed to the decreased binding efficiency of the chloride ion relative to the bromide ion. Variations in the co-ion species (Li, Na, K) have little effect on the adsorption rate and surface excess of CTAC up to a bulk electrolyte concentration of 10 mM. However, the rate of adsorption is increased in the presence of electrolyte. Slow secondary adsorption is seen over a range of concentrations for CTAC in the absence of electrolyte and importantly in the presence of LiCl the origin of this slow adsorption is attributed to a structural barrier to adsorption.
pH-responsive behavior of selectively quaternized diblock copolymers adsorbed at the silica/aqueous solution interface
Publisher: Elsevier BV
Date: 10-2007
DOI: 10.1016/J.JCIS.2007.06.018
Abstract: The desorption and subsequent pH-responsive behavior of selectively quaternized poly(2-(dimethylamino)ethyl methacrylate)-block-poly(2-(diethylamino)ethyl methacrylate) (PDMA-PDEA) films at the silica/aqueous solution interface has been characterized. The copolymer films were prepared at pH 9, where micelle-like surface aggregates are spontaneously formed on silica. The subsequent rinse with a copolymer-free electrolyte solution adjusted to pH 9 causes partial desorption of the weakly or non-quaternized copolymers, but negligible desorption for the highly quaternized copolymers. Further rinsing with a pH 4 electrolyte solution results in additional desorption and extension (swelling) of the remaining adsorbed copolymer film normal to the interface. This pH-responsive behavior is reversible for two pH cycles (9-4-9-4) as monitored by both quartz crystal microbalance with dissipation monitoring (QCM-D) and also zeta potential measurements. The magnitude of the pH-responsive behavior depends on the mean degree of quaternization of the PDMA block. Moreover, a combination of contact angle data, zeta potential measurements and in situ atomic force microscopy (AFM) studies indicates that the pH-responsive behavior is influenced not only by the number of cationic binding sites on the adsorbed copolymer chains but also by the adsorbed layer structure.
Interplay of Composition, pH, and Temperature on the Conformation of Multi-stimulus-responsive Copolymer Brushes: Comparison of Experiment and Theory
Publisher: American Chemical Society (ACS)
Date: 04-05-2020
Specific Ion Effects at the Vapor–Formamide Interface: A Reverse Hofmeister Series in Ion Concentration Depth Profiles
Publisher: American Chemical Society (ACS)
Date: 29-08-2023
Hydrophobic effects within the dynamic pH-response of polybasic tertiary amine methacrylate brushes
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4CP05292G
Abstract: Monomer hydrophobicity dominates the kinetics of the pH-response of tertiary amine methacrylate brushes as determined by in situ ellipsometry and QCM-D kinetic and equilibrium measurements.
Electrostatic formation of polymer particle stabilised liquid marbles and metastable droplets – Effect of latex shell conductivity
Publisher: Elsevier BV
Date: 11-2018
DOI: 10.1016/J.JCIS.2018.04.044
Abstract: Particle cohesion and conductivity affects the electrostatically driven transport of particles to a suspended water droplet. The conditions at which liquid marbles and particle stabilised liquid droplets form are a function of these parameters. Particle beds placed below an earthed pendent water drop had a negative potential applied, thus inducing an opposing positive charge on the liquid, which results in particle transfer and eventual coating of the liquid drop. Experiments where both the particle bed was constantly moved slowly toward the droplet, and the particle bed remained at a fixed, small separation distance were completed. These enabled the investigation of a number of variables that influence successful aggregate formation, including separation distance between the droplet and particle bed, coating mechanism and kinetics of the transfer process. Monodisperse polystyrene core particles with polypyrrole shells of various cohesiveness and conductivity were observed to behave differently in the presence of the applied potential, where the least cohesive and conductive s le (polystyrene) required the smallest separation distance, i.e. the greatest field strength for particle transfer. Increasing conductivity of the particle shell decreases the field strength required for particle transfer, and thus an increase was observed in separation distance at which particles were observed to move to the air-water interface. The transfer kinetics followed the same trend where the least conductive and cohesive s le was the slowest to coat the air-water interface, and vice-versa. Since an increase in cohesion hinders particle transfer, it is concluded that particle conductivity is of greater importance in the electrostatic aggregation process.
Synthesis and Characterization of Novel pH-Responsive Microgels Based on Tertiary Amine Methacrylates
Publisher: American Chemical Society (ACS)
Date: 08-09-2004
DOI: 10.1021/LA049156T
Abstract: Emulsion polymerization of 2-(diethylamino)ethyl methacrylate (DEA) in the presence of a bifunctional cross-linker at pH 8-9 afforded novel pH-responsive microgels of 250-700 nm diameter. Both batch and semicontinuous syntheses were explored using thermal and redox initiators. Various strategies were evaluated for achieving colloidal stability, including charge stabilization, surfactant stabilization, and steric stabilization. The latter proved to be the most convenient and effective, and three types of well-defined reactive macromonomers were examined, namely, monomethoxy-capped poly(ethylene glycol) methacrylate (PEGMA), styrene-capped poly[2-(dimethylamino)ethyl methacrylate] (PDMA50-St), and partially quaternized styrene-capped poly[2-(dimethylamino)ethyl methacrylate] (10qPDMA50-St). The resulting microgels were pH-responsive, as expected. Dynamic light scattering and 1H NMR studies confirmed that reversible swelling occurred at low pH due to protonation of the tertiary amine groups on the DEA residues. The critical pH for this latex-to-microgel transition was around pH 6.5-7.0, which corresponds approximately to the known pKa of 7.0-7.3 for linear PDEA homopolymer. The microgel particles were further characterized by electron microscopy and aqueous electrophoresis studies. Their swelling and deswelling kinetics were investigated by turbidimetry. The PDEA-based microgels were compared to poly[2-(diisopropylamino)ethyl methacrylate] (PDPA) microgels prepared with identical macromonomer stabilizers. These PDPA-based microgels had a lower critical swelling pH of around pH 5.0-5.5, which correlates with the lower pKa of PDPA homopolymer. In addition, the kinetics of swelling for the PDPA microgels was somewhat slower than that observed for PDEA microgels presumably this is related to the greater hydrophobic character of the former particles.
pH-Responsive Brush-Modified Silica Hybrids Synthesized by Surface-Initiated ARGET ATRP
Publisher: American Chemical Society (ACS)
Date: 18-09-2012
DOI: 10.1021/MZ3003566
Abstract: Brush-modified silica hybrids have been synthesized by growing poly(2-(diethylamino)ethyl methacrylate) (poly(DEA)) brushes on 120 nm diameter silica particles by surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (SI-ARGET ATRP). This is the first report of using SI-ARGET ATRP to synthesize poly(DEA) brushes. The kinetics of poly(DEA) brush growth in 4:1 v/v ethanol/water was monitored. The hydrodynamic diameter of the resulting brush-modified particles was dependent on the solution pH due to the weak polybasic nature of the brushes. Below the p
Tunable diblock copolymer micelles–adapting behaviour via subtle chemical modifications
Publisher: Royal Society of Chemistry (RSC)
Date: 2005
DOI: 10.1039/B403180F
Abstract: Selectively quaternising the PDMA block of poly(2-(dimethylamino)ethyl methacrylate)-block-poly(2-(diethylamino)ethyl methacrylate) (PDMA-PDEA) copolymers modifies both their solution and adsorption behaviour. These copolymers exist as free unimers in aqueous solution at low pH and form micelles, with PDMA coronas, at high pH. The critical micellisation pH, the hydrodynamic micelle diameter and electrophoretic behaviour are all affected by the degree of quaternisation of the PDMA block. Highly quaternised copolymers form smaller, more highly charged micelles at lower pH than weakly or non-quaternised copolymers. The adsorption of the copolymer micelles onto muscovite mica is studied by in situ atomic force microscopy. The adsorbed micelle monolayer becomes increasingly disordered as the degree of quaternisation increases. No micelle desorption occurs on removal of the bulk copolymer solution. Addition of acid to the overlying solution leads to different responses from the surface-adsorbed micelles. Unquaternised micelles undergo a reversible change in morphology due to the formation of localised polymer brushes, whereas lightly quaternised micelles are characterised by irreversible changes. Highly quaternised micelle monolayers are disrupted by the addition of acid. Such differences can be rationalised by simple electrostatic arguments. This behaviour has been confirmed by quartz crystal microbalance studies, which show that the adsorbed mass decreases with increasing degrees of quaternisation.
Editorial: Particles at Fluid Interfaces
Publisher: Frontiers Media SA
Date: 07-02-2019
Behavior of Bubble Interfaces Stabilized by Particles of Different Densities
Publisher: American Chemical Society (ACS)
Date: 17-06-2016
DOI: 10.1021/ACS.LANGMUIR.6B00656
Abstract: Stability of bubbles laden with particles of different densities was investigated. Capillary-held bubbles were produced and coated with particles across the density range of 1.2-3.6 g·cm(-3). The materials used were poly(methyl methacrylate) (PMMA), glass, and anatase. The interaction of the bubbles, once brought into contact, was monitored using high-speed video recording. Visual inspection indicated that denser particles were more easily displaced during the contact of the bubbles and therefore the PMMA particles provided a particle barrier more resistant to coalescence. The coalescence events yielded information on the surface properties of the bubble and the detachment of particles. The attached particles commonly d en the oscillation of the coalesced bubbles through viscous drag and change in the surface properties (e.g., area-exclusion principle). The d ening of the oscillation generally leads to a reduced mass of particles detaching from the bubble surface. It was found that the different materials investigated did not offer clear evidence of the effect of particle detachment on the bubble surface properties in the present systems. On the other hand, the detachment of different particle materials seemed to be consistent with one another when comparing the attachment and detachment forces exerted on the particles based on their density, size, and hydrophobicity. It was concluded that particles of lower density are more effective in stabilizing interfaces, and thus particle density is an important parameter in the selection of materials for the handling of dispersions.
Liquid marble and water droplet interactions and stability
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5SM01584G
Abstract: The interactions between two in idual water droplets were investigated in air using a combination of coalescence rig and high speed video camera.
Poly(N-isopropylacrylamide) Response to Salt Concentration and Anion Identity: A Brush-on-Brush Study
Publisher: American Chemical Society (ACS)
Date: 24-07-2019
DOI: 10.1021/ACS.LANGMUIR.9B00695
Abstract: The stability of poly(
Enhanced Flocculation Efficiency in a High-Ionic-Strength Environment by the Aid of Anionic ABA Triblock Copolymers
Publisher: American Chemical Society (ACS)
Date: 23-01-2020
DOI: 10.1021/ACS.LANGMUIR.9B03689
Abstract: The flocculation efficiency of polyelectrolytes in a high-ionic-strength environment is often affected and reduced due to shielding of the active ionizable functional groups, as well as changes in the surface chemistry of the solid slurry. To address this problem, a series of well-defined novel ABA triblock copolymers were employed for the flocculation of high-ionic-strength kaolin slurries at three different Ca
Dispersion stability of a ceramic glaze achieved through ionic surfactant adsorption
Publisher: Elsevier BV
Date: 11-2004
Interparticle Repulsion of Microparticles Delivered to a Pendent Drop by an Electric Field
Publisher: American Chemical Society (ACS)
Date: 30-12-2021
DOI: 10.1021/ACS.LANGMUIR.1C02507
Abstract: We report an unusually large spacing observed between microparticles after delivery to the surface of a pendent water droplet using a DC nonuniform electrostatic field, primarily via dielectrophoresis. The influence of particle properties was investigated using core particles, which were either coated or surface-modified to alter their wettability and conductivity. Particles that exhibited this spacing were both hydrophobic and possessed some dielectric material exposed to the external field, such as a coating or exposed dielectric core. The origin of this behavior is proposed to be the induced dipole-dipole repulsion between particles, which increases with particle size and decreases when the magnitude of the electric field is reduced. When the particles were no longer subjected to an external field, this large interparticle repulsion ceased and the particles settled to the bottom of the droplet under the force of gravity. We derive a simple model to predict this spacing, with the dipole-dipole repulsion balanced against particle weight. The external electric field was calculated using the existing electric field models. The spacing was found to be dependent on particle density and the induced dipole moment as well as the number of particles present on the droplet interface. As the number of particles increased, a decrease in interparticle spacing was observed.
Cosolvent effects on the structure and thermoresponse of a polymer brush: PNIPAM in DMSO–water mixtures
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D2PY01487D
Abstract: Structural characterisation of thermoresponsive polymer brushes in binary DMSO–water mixtures reveals both LCST and UCST behaviour.
pH-Responsive Diblock Copolymer Micelles at the Silica/Aqueous Solution Interface: Adsorption Kinetics and Equilibrium Studies
Publisher: American Chemical Society (ACS)
Date: 08-07-2006
DOI: 10.1021/JP062830Q
Abstract: The adsorption behavior of two ex les of a weakly basic diblock copolymer, poly(2-(dimethylamino)ethyl methacrylate)-block-poly(2-(diethylamino)ethyl methacrylate) (PDMA-PDEA), at the silica/aqueous solution interface has been investigated using a quartz crystal microbalance with dissipation monitoring and an optical reflectometer. Dynamic and static light scattering measurements have also been carried out to assess aqueous solution properties of such pH-responsive copolymers. In alkaline solution, core-shell micelles are formed above the critical micelle concentration (cmc) by both copolymers, whereas the chains are molecularly dissolved (as unimers) at all concentrations in acidic solution. As a result, the adsorption behavior of PDMA-PDEA diblock copolymers on silica is strongly dependent on both the copolymer concentration and the solution pH. Below the cmc at pH 9, the cationic PDMA-PDEA copolymers adsorb as unimers and the conformation of the adsorbed polymer is essentially flat. At concentrations just above the cmc, the initial adsorption of copolymer onto the silica is dominated by the unimers due to their faster diffusion compared to the much larger micelles. Rearrangement of the adsorbed unimers and/or their subsequent displacement by micelles from solution is then observed during an equilibration period, and the final adsorbed mass is greater than that observed below the cmc. At concentrations well above the cmc, the much higher proportion of micelles in solution facilitates more effective competition for the surface at all stages of the adsorption process and no replacement of initially adsorbed unimers by micelles is evident. However, the adsorbed layer undergoes gradual rearrangement after initial adsorption. This relaxation is believed to result from a combination of further copolymer adsorption and swelling of the adsorbed layer.
Surface and aqueous solution properties of a highly charged cage surfactant
Publisher: Elsevier BV
Date: 1991
Interaction between surfaces in ethanol: Adsorption, capillary condensation, and solvation forces
Publisher: AIP Publishing
Date: 09-1994
DOI: 10.1063/1.467476
Abstract: When two surfaces in a condensable vapor are brought together, the vapor will capillary condense in the narrow gap between the surfaces. The surface forces apparatus, (SFA) has been used to study this condensation process with mica surfaces in ethanol vapor close to saturation. In particular, the critical surface separation at which the condensed bridge forms has been quantified. For thin adsorbed films (≤2 nm), the results are not consistent with a model of a liquid bridge formed by adsorbed films thickening under the influence of van der Waals forces. Instead, nucleation from vapor in the gap between the surfaces is possibly contributing to the formation of the bridge. The short-range interaction of mica surfaces in near-saturated ethanol vapor is also presented. The contact adhesion is much smaller than in nonpolar liquids due to the shielding of the ionic components of the adhesion. The solvation force is found to be similar to that in nonpolar liquids, except that the innermost minima are deeper. This is attributed to the hiphilic nature of the ethanol molecule.
Stimulus-Responsive Soft Surface/Interface Toward Applications in Adhesion, Sensor and Biomaterial
Publisher: Springer International Publishing
Date: 2018
Understanding specific ion effects and the Hofmeister series
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2CP00847E
Abstract: This perspective reviews the historical explanations for specific ion effects, and explores the frontiers of the field before summarising its challenges and opportunities.
Direct Observation of Giant Pickering Emulsion and Colloidosome Droplet Interaction and Stability
Publisher: American Chemical Society (ACS)
Date: 20-11-2012
DOI: 10.1021/LA3025765
Abstract: The interactions of two 2-mm pendant oil droplets grown in the presence of an aqueous solution of poly(glycerol monomethacrylate)-stabilized polystyrene latex particles was observed using a high-speed video camera. The coalescence behavior was monitored as a function of oil type (n-dodecane versus sunflower oil) and particle size (135 versus 902 nm), as well as in the presence and absence of an oil-soluble cross-linker [tolylene 2,4-diisocyanate-terminated poly(propylene glycol)]. The d ing coefficient of the coalescing n-dodecane droplets was found to increase in the presence of the latex, demonstrating particle adsorption. Coalescence times increased when the oil phase was changed from n-dodecane to sunflower oil, because of the much higher viscosity of the latter oil. In addition, increasing the adsorbed particle size from 135 to 902 nm led to longer coalescence times because of the greater distance separating the oil droplets. Coalescence times observed in the presence of the larger 902-nm particles indicated that two different modes of contact can occur prior to a coalescence event (bilayer or bridging monolayer of particles in the film). Addition of an oil-soluble surface-active cross-linker to the sunflower oil phase to react with the hydroxy groups of the particle stabilizer reduced the interfacial elasticity and ultimately prevented coalescence after cross-linking for 20 min at 25 °C. Such giant colloidosomes can remain in contact for several hours without undergoing coalescence, which demonstrates their high stability. Furthermore, coalescence is prevented even if the cross-linker is present in only one of the pendant droplets. Finally, evidence for cross-linker diffusion from one pendant droplet to another was indicated by a visible filament connecting the two droplets upon retraction.
Combined Experimental and Theoretical Study of Weak Polyelectrolyte Brushes in Salt Mixtures
Publisher: American Chemical Society (ACS)
Date: 20-01-2019
Quantifying the robustness of the neutron reflectometry technique for structural characterization of polymer brushes
Publisher: International Union of Crystallography (IUCr)
Date: 16-04-2021
DOI: 10.1107/S160057672100251X
Abstract: Neutron reflectometry is the foremost technique for in situ determination of the volume fraction profiles of polymer brushes at planar interfaces. However, the subtle features in the reflectometry data produced by these diffuse interfaces challenge data interpretation. Historically, data analyses have used least-squares approaches that do not adequately quantify the uncertainty of the modeled profile and ignore the possibility of other structures that also match the collected data (multimodality). Here, a Bayesian statistical approach is used that permits the structural uncertainty and multimodality to be quantified for polymer brush systems. A free-form model is used to describe the volume fraction profile, minimizing assumptions regarding brush structure, while only allowing physically reasonable profiles to be produced. The model allows the total volume of polymer and the profile monotonicity to be constrained. The rigor of the approach is demonstrated via a round-trip analysis of a simulated system, before it is applied to real data examining the well characterized collapse of a thermoresponsive brush. It is shown that, while failure to constrain the interfacial volume and consider multimodality may result in erroneous structures being derived, carefully constraining the model allows for robust determination of polymer brush compositional profiles. This work highlights that an appropriate combination of flexibility and constraint must be used with polymer brush systems to ensure the veracity of the analysis. The code used in this analysis is provided, enabling the reproduction of the results and the application of the method to similar problems.
Dynamics of Adsorption of Cationic Surfactants at Air-Water and Solid-Liquid Interfaces
Publisher: CRC Press
Date: 30-03-2005
Simultaneous electrochemical-assisted exfoliation and in situ surface functionalization towards large-scale production of few-layer graphene
Publisher: Elsevier BV
Date: 11-2019
Fractal-like R5 assembly promote the condensation of silicic acid into silica particles
Publisher: Elsevier BV
Date: 09-2021
There's no harm in having too much: A comprehensive toolbox of methods in trophic ecology
Publisher: Elsevier BV
Date: 12-2018
Morphology Transitions in Nonionic Surfactant Adsorbed Layers near Their Cloud Points
Publisher: American Chemical Society (ACS)
Date: 22-10-2005
DOI: 10.1021/LA0520334
Abstract: The structure of adsorbed layers of several polyoxyethylene alkyl ether (C(n)E(m)) nonionic surfactants on silica and graphite surfaces has been imaged using atomic force microscopy as a function of temperature up to their cloud points. For all surfactants with a cloud point within the experimentally accessible range, the adsorbed layer morphology on silica evolved from globules at low temperatures first into rods and then a mesh with increasing temperature. This mesh structure was retained even when the solutions were heated above their cloud points into the two-phase coexistence region. Only C(12)E(3) was observed to form a laterally unstructured bilayer. On graphite, all surfactants formed straight, parallel hemicylinders at all temperatures examined.
Adsorption of Amphiphilic Diblock Copolymer Micelles at the Mica/Solution Interface
Publisher: American Chemical Society (ACS)
Date: 27-07-2001
DOI: 10.1021/LA010335+
Microcapsules Fabricated from Liquid Marbles Stabilized with Latex Particles
Publisher: American Chemical Society (ACS)
Date: 12-03-2014
DOI: 10.1021/LA5003435
Abstract: Millimeter- and centimeter-sized "liquid marbles" were readily prepared by rolling water droplets on a powder bed of dried submicrometer-sized polystyrene latex particles carrying poly[2-(diethylamino)ethyl methacrylate] hairs (PDEA-PS). Scanning electron microscopy studies indicated that flocs of the PDEA-PS particles were adsorbed at the surface of these water droplets, leading to stable spherical liquid marbles. The liquid marbles were deformed as a result of water evaporation to adopt a deflated spherical geometry, and the rate of water evaporation decreased with increasing atmospheric relative humidity. Conversely, liquid marbles formed using saturated aqueous LiCl solution led to atmospheric water absorption by the liquid marbles and a consequent mass increase. The liquid marbles can be transformed into polymeric capsules containing water by exposure to solvent vapor: the PDEA-PS particles were plasticized with the solvent vapor to form a polymer film at the air-water interface of the liquid marbles. The polymeric capsules with aqueous volumes of 250 μL or less kept their oblate ellipsoid/near spherical shape even after complete water evaporation, which confirmed that a rigid polymeric capsule was successfully formed. Both the rate of water evaporation from the pure water liquid marbles and the rate of water adsorption into the aqueous LiCl liquid marbles were reduced with an increase of solvent vapor treatment time. This suggests that the number and size of pores within the polymer particles/flocs on the liquid marble surface decreased due to film formation during exposure to organic solvent vapor. In addition, organic-inorganic composite capsules and colloidal crystal capsules were fabricated from liquid marbles containing aqueous SiO2 dispersions.
Nano-anemones: Stimulus-responsive copolymer-micelle surfaces
Publisher: Wiley
Date: 18-10-2004
Polydimethylsiloxane-Based Giant Glycosylated Polymersomes with Tunable Bacterial Affinity
Publisher: American Chemical Society (ACS)
Date: 29-01-2019
DOI: 10.1021/ACS.BIOMAC.8B01709
Abstract: A synthetic cell mimic in the form of giant glycosylated polymersomes (GGPs) comprised of a novel hiphilic diblock copolymer is reported. A synthetic approach involving a poly(dimethylsiloxane) (PDMS) macro-chain transfer agent (macroCTA) and postpolymerization modification was used to marry the hydrophobic and highly flexible properties of PDMS with the biological activity of glycopolymers. 2-Bromoethyl acrylate (BEA) was first polymerized using a PDMS macroCTA ( M
Lewis Strength Determines Specific-Ion Effects in Aqueous and Nonaqueous Solvents
Publisher: American Chemical Society (ACS)
Date: 21-06-2019
Abstract: An analysis of specific-ion effects in aqueous and nonaqueous solvents using energy decomposition analysis is presented. Specific-ion effects induce or influence physicochemical phenomena in a way that is determined by the identity of the ions present, and not merely by their charge or concentration. Such effects have been known since the seminal work of Hofmeister and are often categorized according to the well-known Hofmeister series. Ex les of specific-ion effects are ubiquitous throughout chemistry and biology and are traditionally explained in terms of the influence ions have on the structure of water. However, this explanation is unsatisfactory because it is unable to adequately explain and predict frequently observed series reversals and anomalies. Further, recent experiments have shown that specific-ion effects are observed in nonaqueous solvents. By modeling solvated ion-
A new electrochemical cell for atomic force microscopy
Publisher: AIP Publishing
Date: 04-1994
DOI: 10.1063/1.1145108
Abstract: Described is the design for a new electrochemical cell for in situ studies with the atomic force microscope. Improvements over presently used cells include an axially symmetric electrode geometry, large counter electrode, and the ability to incorporate a standard reference electrode close to the working electrode.
The role of copolymer composition on the specific ion and thermo-response of ethylene glycol-based brushes
Publisher: Elsevier BV
Date: 02-2018
Nonequilibrium mesoscale surface structures: The adsorption of polymer-surfactant mixtures at the solid/liquid interface
Publisher: American Chemical Society (ACS)
Date: 17-11-1999
DOI: 10.1021/LA990588R
Imaging Proton Transport in Giant Vesicles through Cyclic Peptide–Polymer Conjugate Nanotube Transmembrane Ion Channels
Publisher: Wiley
Date: 16-02-2018
Abstract: Since their discovery in 1993, interest in various aspects of cyclic peptides (CPs) has expanded rapidly. Of particular note is their potential to form artificial ion channels in lipid membranes, an attractive characteristic in supramolecular chemistry and biological research. The design and synthesis of cyclic peptide-polymer conjugates (CPPCs) that can self-assemble within lipid bilayers into nanotubes, mimicking naturally occurring membrane channels and pores, has been reported. However, methods that allow direct detection of the transport process with high levels of certainty are still lacking. This work focuses on the development of a simple but reliable approach to verify and quantify proton transport across a bilayer membrane. Giant unilamellar vesicles (GUVs) are created via the electroformation method and CPPCs are incorporated in GUV membranes at varying concentrations (0-10%). Confocal fluorescence microscopy is used to demonstrate full inclusion of fluorescein-labeled CPPCs in the GUV membranes. The pH-sensitive dye carboxyfluorescein is encapsulated within the water pool of the GUVs and used as an indicator of proton transport. This assay is versatile and can be exploited on other existing proton transporter systems, providing a consistent tool to compare their performances. It should also aid the development of novel antineoplastics and drug delivery systems.
Adsorption of Submicrometer-Sized Cationic Sterically Stabilized Polystyrene Latex at the Air−Water Interface: Contact Angle Determination by Ellipsometry
Publisher: American Chemical Society (ACS)
Date: 12-02-2009
DOI: 10.1021/LA803879P
Abstract: Near-monodisperse, sterically stabilized cationic polystyrene latexes of either 122 or 310 nm diameter were prepared by aqueous emulsion polymerization using cheap, readily available reagents. At low pH, these latexes stabilized foams prepared by either hand-shaking or by using a foam column. SEM studies confirmed that the dried foam mainly comprised well-defined bilayers, which suggests that each air bubble is stabilized with a latex monolayer. Adsorption of the same latexes at the planar air-water interface was studied using the Langmuir-Blodgett trough technique. Surface pressure isotherms confirmed particle desorption from the interface on repeated compression of the latex monolayers. For the 122 nm latex at pH 2, ellipsometric analysis enabled a contact angle of approximately 43 degrees to be calculated from a simple two-layer model, which suggests that these particles have only moderate wettability. Similar results were obtained for the 310 nm latex, but the data were much less reliable in this case due to additional background particle scattering.
Adsorption of 12-s-12 Gemini Surfactants at the Silica−Aqueous Solution Interface
Publisher: American Chemical Society (ACS)
Date: 07-03-2003
DOI: 10.1021/JP026626O
Interaction forces between silica surfaces in aqueous solutions of cationic polymeric flocculants: Effect of polymer chargen
Publisher: American Chemical Society (ACS)
Date: 27-08-2008
DOI: 10.1021/LA801109N
Abstract: Three cationic polymers with molecular weights and charge density of 3.0 x 10(5) g/mol and 10% (D 6010), 1.1 x 10(5) g/mol and 40% (D6040), and 1.2 x 10(5) g/mol and 100% (D6099) were investigated in aqueous NaCl solutions in the presence of silica. The atomic force microscope (AFM) colloidal probe technique was used to determine silica interparticle interaction forces, which were compared to macroscopic information on the strength of interactions such as compressive yield stress measurements. It was found that in 30 mM NaCl solution the 10% charged polymer produced steric repulsion upon approach and long-range adhesion with multiple pull off events upon retraction at the optimum flocculation concentration. This suggests that the polymer was adsorbed in a conformation where segments extend from the surface, resulting in bridging flocculation. The 40 and 100% charged polymers produced attraction upon approach and strong adhesion with snap out from contact upon separation at optimum polymer dosages. This suggests that these polymers are adsorbed with flat conformations and is typical of charge neutralization or patch attraction. The attractions for 40 and 100% charged polymers measured with the AFM are significantly larger than for the 10% charged polymer. The polymer dose that produced the optimum flocculation and the maximum compressive yield stress typically corresponded to the polymer concentration that produced the maximum adhesion for each polymer. It was found that the magnitude of the adhesive force was more significant in determining the compressive yield stresses of the silica particle sediments than the aggregate size and structure.
Mechanism of cationic surfactant adsorption at the solid–aqueous interface
Publisher: Elsevier BV
Date: 05-2003
Direct Observation of pH-Induced Coalescence of Latex-Stabilized Bubbles Using High-Speed Video Imaging
Publisher: American Chemical Society (ACS)
Date: 23-04-2010
DOI: 10.1021/LA904708X
Abstract: The coalescence of pairs of 2 mm air bubbles grown in a dilute electrolyte solution containing a lightly cross-linked 380 nm diameter PEGMA-stabilized poly(2-vinylpyridine) (P2VP) latex was monitored using a high-speed video camera. The air bubbles were highly stable at pH 10 when coated with this latex, although coalescence could be induced by increasing the bubble volume when in contact. Conversely, coalescence was rapid when the bubbles were equilibrated at pH 2, since the latex undergoes a latex-to-microgel transition and the swollen microgel particles are no longer adsorbed at the air-water interface. Rapid coalescence was also observed for latex-coated bubbles equilibrated at pH 10 and then abruptly adjusted to pH 2. Time-dependent postrupture oscillations in the projected surface area of coalescing P2VP-coated bubble pairs were studied using a high-speed video camera in order to reinvestigate the rapid acid-induced catastrophic foam collapse previously reported [Dupin, D. et al. J. Mater. Chem. 2008, 18, 545]. At pH 10, the P2VP latex particles adsorbed at the surface of coalescing bubbles reduce the oscillation frequency significantly. This is attributed to a close-packed latex monolayer, which increases the bubble stiffness and hence restricts surface deformation. The swollen P2VP microgel particles that are formed in acid also affected the coalescence dynamics. It was concluded that there was a high concentration of swollen microgel at the air-water interface, which created a localized, viscous surface gel layer that inhibited at least the first period of the surface area oscillation. Close comparison between latex-coated bubbles at pH 10 and those coated with 66 microm spherical glass beads indicated that the former system exhibits more elastic behavior. This was attributed to the compressibility of the latex monolayer on the bubble surface during coalescence. A comparable elastic response was observed for similar sized titania particles, suggesting that particle size is a significant factor in defining the interfacial elasticity of particle-coated bubbles.
Competitive specific ion effects in mixed salt solutions on a thermoresponsive polymer brush
Publisher: Elsevier BV
Date: 03-2021
Electrostatic formation of Liquid Marbles – Statistical model
Publisher: IOP Publishing
Date: 10-2019
DOI: 10.1088/1742-6596/1322/1/012006
Abstract: A statistical treatment is developed for the electrostatic transfer of particles from a powder bed to a pendent droplet during liquid marble and aggregate formation. The model uses Weibull statistics to calculate the probability of particle transfer events of a given size occurring, for the given electric field strength and geometry. This is used in Monte Carlo simulations of the transfer process. In this preliminary study, some of the most distinctive features of the experiments – transfer event size and spacing, scaling with driving potential – are well-captured using physically plausible parameter values. Other features, such as denuding of the particle bed, are less well reproduced, and require refinement.
Computer simulations of particle-bubble interactions and particle sliding using Discrete Element Method
Publisher: Elsevier BV
Date: 09-2012
DOI: 10.1016/J.JCIS.2012.05.021
Abstract: Three dimensional Discrete Element Method (DEM) computer simulations have been carried out to analyse the kinetics of collision of multiple particles against a stationary bubble and the sliding of the particles over the bubble surface. This is the first time that a computational analysis of the sliding time and particle packing arrangements of multiple particles on the surface of a bubble has been carried out. The collision kinetics of monodisperse (33 μm in radius) and polydisperse (12-33 μm in radius) particle systems have been analysed in terms of the time taken by 10%, 50% and 100% of the particles to collide against the bubble. The dependencies of these collision times on the strength of hydrophobic interactions follow relationships close to power laws. However, minimal sensitivity of the collision times to particle size was found when linear and square relationships of the hydrophobic force with particles radius were considered. The sliding time for single particles has corroborated published theoretical expressions. Finally, a good qualitative comparison with experiments has been observed with respect to the particle packing at the bottom of the bubble after sliding demonstrating the usefulness of computer simulations in the studies of particle-bubble systems.
The electrostatic origins of specific ion effects: quantifying the Hofmeister series for anions
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1SC03568A
Abstract: Analysis of ions’ radial charge densities reveals they correlate with many specific ion effects, and provides a new basis to explain and quantify the 130-year-old Hofmeister series for anions.
Exploring the Impact of Particle Material Properties on Electrostatic Liquid Marble Formation
Publisher: American Chemical Society (ACS)
Date: 19-11-2020
Physicochemical behaviour of cationic polyelectrolyte brushes
Publisher: Elsevier BV
Date: 2017
Formation of Liquid Marbles Using pH-Responsive Particles: Rolling vs Electrostatic Methods
Publisher: American Chemical Society (ACS)
Date: 09-04-2018
DOI: 10.1021/ACS.LANGMUIR.7B04204
Abstract: Aqueous dispersions of micrometer-sized, monodisperse polystyrene (PS) particles carrying pH-responsive poly[2-(diethylamino)ethyl methacrylate] (PDEA) colloidal stabilizer on their surfaces were dried under ambient conditions at pH 3.0 and 10.0. The resulting dried cake-like particulate materials were ground into powders and used as a stabilizer to fabricate liquid marbles (LMs) by rolling and electrostatic methods. The powder obtained from pH 3.0 aqueous dispersion consisted of polydisperse irregular-shaped colloidal crystal grains of densely packed colloids which had hydrophilic character. On the other hand, the powder obtained from pH 10.0 aqueous dispersion consisted of amorphous and disordered colloidal aggregate grains with random sizes and shapes, which had hydrophobic character. Reflecting the hydrophilic-hydrophobic balance of the dried PDEA-PS particle powders, stable LMs were fabricated with distilled water droplets by rolling on the powders prepared from pH 10.0, but the water droplets were adsorbed into the powders prepared from pH 3.0. In the electrostatic method, where an electric field assists transport of powders to a droplet surface, the PDEA-PS powders prepared from pH 3.0 jumped to an earthed pendant distilled water droplet to form a droplet of aqueous dispersion. Conversely the larger powder aggregates prepared from pH 10.0 did not jump due to cohesion between the hydrophobic PDEA chains on the PS particles, resulting in no LM formation.
In situ observations of adsorbed microgel particles
Publisher: Royal Society of Chemistry (RSC)
Date: 2007
DOI: 10.1039/B613981G
Effect of esterically bonded agents on the monolayer structure and foamability of nano-silica
Publisher: Elsevier BV
Date: 02-2009
Specific Anion Effects on the Internal Structure of a Poly(N-isopropylacrylamide) Brush
Publisher: American Chemical Society (ACS)
Date: 05-08-2016
A multilayered approach to polyfluorene water-based organic photovoltaics
Publisher: Elsevier BV
Date: 07-2012
A study of factors affecting women’s lived experiences in STEM
Publisher: Springer Science and Business Media LLC
Date: 06-04-2022
DOI: 10.1057/S41599-022-01136-1
Abstract: The number of women employed in STEM in Australia is increasing, however, they continue to remain underrepresented in most industries. A significant corpus of literature on female underrepresentation has emerged in the past 20 years, however, many of those studies focus on educational access and retention and not many look at the lived experiences of women after they have left higher education. In this article, we take a different stance and explore the heterogeneous experiences of female STEM professionals in regional Australia. Through the qualitative analysis of 25 interviews, we learn what women have endured, accepted, and valued on their in idual STEM journeys. While these journeys are often quite different, our interviewees independently reported having experienced similar societal prejudices and possessing similar personality traits. Our data reveals that resilience and determination proved vital for these women, as did a strong early interest in STEM. Our interviews also unearth issues in which women’s opinions are fiercely ided, such as whether positive discrimination has been a barrier or an enabler for their careers. Based on what we have learnt from their accounts, we argue that these women have ‘survived’ their work environments despite structural barriers, only due to their determination, resilience and fervent interest.
refellips: A Python package for the analysis of variable angle spectroscopic ellipsometry data
Publisher: Elsevier BV
Date: 12-2022
Growth of Double-Chained Cationic Surfactant Films on Mica
Publisher: CSIRO Publishing
Date: 2006
DOI: 10.1071/CH06069
Abstract: The evolution of adsorbed dialkyl chained quaternary ammonium surfactant films with different alkyl chain lengths has been observed in situ using atomic force microscopy (AFM). Both di-C12DAB and di-C14DAB form a cohesive bilayer immediately, which is observed to strengthen with equilibration time. The slow equilibrium of di-C16DAB allows examination of the film at less than saturated coverage and reveals growth of the bilayer through the nucleation and coalescence of patches. The difference in height between higher and lower regions is insufficient for bilayer and monolayer regions and the postulated structure is that of regions of bilayer with different packing densities. The effect of temperature on film morphologies near the gel transition is also examined.
Comparing polymer-surfactant complexes to polyelectrolytes
Publisher: Elsevier BV
Date: 10-2023
Decomposing Hofmeister effects on amino acid residues with symmetry adapted perturbation theory
Publisher: IOP Publishing
Date: 03-2023
Abstract: Hofmeister effects, and more generally specific ion effects, are observed broadly in biological systems. However, there are many cases where the Hofmeister series might not be followed in complex biological systems, such as ion channels which can be highly specific to a particular ion. An understanding of how ions from the Hofmeister series interact with the proteinogenic amino acids will assist elucidation of why some binding interactions may be favoured over others. Using symmetry adapted perturbation theory (SAPT2 + 3), the interaction energies between a selection of anions and each amino acid have been investigated. The interaction strengths become more favourable in accordance with the Hofmeister series, and also with increasing polarity of the amino acids (with the exception of the negatively charged amino acid side chains). Furthermore, the interactions are generally most favourable when they simultaneously involve the side chain and both protic moieties of the backbone. The total interaction energy in these anion–amino acid complexes is also primarily determined by its electrostatic component, in a manner proportional to the þ (‘sho’) value of the anion.
Gypsum–anhydrite transformation in hot acidic manganese sulfate solution. A comparative kinetic study employing several analytical methods
Publisher: Elsevier BV
Date: 11-2004
Computational analysis of the selective capture of binary mixtures of particles by a bubble in quiescent and fluid flow
Publisher: Elsevier BV
Date: 05-2016
Underscreening in concentrated electrolytes: Re-entrant swelling in polyelectrolyte brushes
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3CP02206D
Abstract: Hypersaline environments are ubiquitous in nature and are found in myriad technological processes. Recent empirical studies have revealed a significant discrepancy between the predicted and observed screening lengths at high...
Nature of the Specific Anion Response of a Hydrophobic Weak Polyelectrolyte Brush Revealed by AFM Force Measurements
Publisher: American Chemical Society (ACS)
Date: 04-03-2016
Comparison of the Adsorption of Cationic Diblock Copolymer Micelles from Aqueous Solution onto Mica and Silica
Publisher: American Chemical Society (ACS)
Date: 05-05-2006
DOI: 10.1021/LA060662N
Abstract: The similarities and differences in the adsorption behavior of diblock poly(2-(dimethylamino)ethyl methacrylate)-b-poly(2-(diethylamino)ethyl methacrylate) (XqPDMA-PDEA, where X refers to a mean degree of quaternization of the PDMA of either 0, 10, 50, or 100 mol%) copolymers at the mica/ and silica/aqueous solution interfaces have been investigated. These diblock copolymers form core-shell micelles with the PDEA chains located in the cores and the more hydrophilic PDMA chains forming the cationic micelle coronas at pH 9. These micelles adsorb strongly onto both mica and silica due to electrostatic interactions. In situ atomic force microscopy (AFM) has demonstrated that the mean spacing and the dimension of the adsorbed micelles depend on both the substrate and the mean degree of quaternization of the PDMA blocks. In particular, the morphology of the adsorbed nonquaternized 0qPDMA-PDEA copolymer micelles is clearly influenced by the substrate type: these micelles form a disordered layer on silica, while much more close-packed, highly ordered layers are obtained on mica. The key reasons for this difference are suggested to be the ease of lateral rearrangement for the copolymer micelles attached to the solid substrates and the relative rates of relaxation of the coronal PDMA chains.
Electrostatic formation of liquid marbles - Influence of drop and particle size
Publisher: Elsevier BV
Date: 12-2016
Science with the Cherenkov Telescope Array
Publisher: WORLD SCIENTIFIC
Date: 26-02-2018
DOI: 10.1142/10986
Liquid marbles, formation and locomotion using external fields and forces
Publisher: Elsevier BV
Date: 06-2021
Adsorbed and near-surface structure of ionic liquids determines nanoscale friction
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3CC42844C
DEM modelling of particle-bubble capture through extended DLVO theory
Publisher: Elsevier BV
Date: 09-2017
Adsorption of Hexadecyltrimethylammonium Bromide to Mica: Nanometer-Scale Study of Binding-Site Competition Effects
Publisher: American Chemical Society (ACS)
Date: 04-12-1998
DOI: 10.1021/LA9710942
Weak influence of divalent ions on anionic surfactant surface-aggregation
Publisher: American Chemical Society (ACS)
Date: 03-1997
DOI: 10.1021/LA960861E
Characterizing the pH-Responsive Behavior of Thin Films of Diblock Copolymer Micelles at the Silica/Aqueous Solution Interface
Publisher: American Chemical Society (ACS)
Date: 09-2006
DOI: 10.1021/LA061708F
Abstract: The pH-responsive behavior of cationic diblock poly(2-(dimethylamino)ethyl methacrylate)-block-poly(2-(diethylamino)ethyl methacrylate) copolymer micelles adsorbed at the silica/aqueous solution interface has been characterized. The micellar morphology of this copolymer, initially adsorbed at pH 9, can be dramatically altered by lowering the solution pH. The original micelle-like morphology of the adsorbed copolymer chains at pH 9 completely disappears as the pH is decreased to 4, and a brush-like layer structure is produced. This change results from protonation of the copolymer chains: the subsequent electrostatic repulsions within the film drive the copolymer chains to expand into the aqueous phase. Returning the solution pH from 4 to 9 causes this brush-like layer to collapse, with atomic force microscopy images suggesting degradation of the film. Hence, the pH-responsive behavior of the copolymer film exhibits irreversible morphological changes. Measurements of the adsorbed/desorbed amounts of the copolymer film were conducted using both a quartz crystal microbalance with dissipation monitoring (QCM-D) and optical reflectometry (OR). After an initial rinse at both pH values, the OR adsorbed mass becomes almost constant during subsequent pH cycling, whereas the corresponding QCM-D adsorbed mass changes significantly but reversibly in response to the solution pH. Since the QCM-D measures a bound mass that moves in tandem with the surface, the discrepancy with the OR data is due to changes in the amount of bound water in the copolymer film as a result of the pH-induced changes in surface morphology. The larger effective mass observed at pH 4 suggests that the brush-like layer contains much more entrapped water than the micellar films at pH 9. The pH dependence of the contact angle of the adsorbed film is consistent with the changes observed using the other techniques, regardless of whether the solution pH is altered in situ or the aqueous solution is completely replaced. In fact, comparison of these two approaches provides direct evidence of the exposure of adsorbed micelle core blocks to the solution during pH cycling and the concomitant impact upon all the other measurements.
Giant pH-responsive microgel colloidosomes: preparation, interaction dynamics and stability
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C5SM02450A
Abstract: Cross-linked PTBAEMA-stabilised colloidosomes are still present after the acid-induced latex-to-microgel transition unlike the analogous Pickering droplets which coalesce.
Adsorption of Ionic Surfactants to a Plasma Polymer Substrate
Publisher: American Chemical Society (ACS)
Date: 09-04-2003
DOI: 10.1021/LA026852P
Clinical trials knowledge and attitudes of Vietnamese- and Anglo-Australian cancer patients: A cross-sectional study.
Publisher: Wiley
Date: 10-08-2020
DOI: 10.1111/AJCO.13388
Australian colloid and surface science in 2007
Publisher: CSIRO Publishing
Date: 2007
DOI: 10.1071/CH07293
Preparation and Characterization of Colloidal Silica Particles under Mild Conditions
Publisher: American Chemical Society (ACS)
Date: 27-04-2012
DOI: 10.1021/ED200684S
Particle-liquid structures formed by electric fields
Publisher: Elsevier BV
Date: 09-2016
DEM simulation of single bubble flotation: Implications for the hydrophobic force in particle-bubble interactions
Publisher: Elsevier BV
Date: 07-2014
Anion-specific effects on the behavior of pH-sensitive polybasic brushes
Publisher: American Chemical Society (ACS)
Date: 23-03-2015
DOI: 10.1021/ACS.LANGMUIR.5B00116
Abstract: The anion-specific solvation and conformational behavior of weakly basic poly(2-dimethylamino)ethyl methacrylate (poly(DMA)), poly(2-diethylamino)ethyl methacrylate (poly(DEA)), and poly(2-diisopropylamino)ethyl methacrylate (poly(DPA)) brushes, with correspondingly increasing inherent hydrophobicity, have been investigated using in situ ellipsometric and quartz crystal microbalance with dissipation (QCM-D) measurements. In the osmotic brush regime, as the initial low concentration of salt is increased, the brushes osmotically swell by the uptake of solvent as they become charged and the attractive hydrophobic inter- and intrachain interactions are overcome. With increased ionic strength, the brushes move into the salted brush regime where they desolvate and collapse as their electrostatic charge is screened. Here, as the brushes collapse, they transition to more uniform and rigid conformations, which dissipate less energy, than similarly solvated brushes at lower ionic strength. Significantly, in these distinct regimes brush behavior is not only ionic strength dependent but is also influenced by the nature of the added salt based on its position in the well-known Hofmeister or lyotropic series, with potassium acetate, nitrate, and thiocyanate investigated. The strongly kosmotropic acetate anions display low affinity for the hydrophobic polymers, and largely unscreened electrosteric repulsions allow the brushes to remain highly solvated at higher acetate concentrations. The mildly chaotropic nitrate and strongly chaotropic thiocyanate anions exhibit a polymer hydrophobicity-dependent affinity for the brushes. Increasing thiocyanate concentration causes the brushes to collapse at lower ionic strength than for the other two anions. This study of weak polybasic brushes demonstrates the importance of all ion, solvent, and polymer interactions.
Ultra-fast aqueous polymerisation of acrylamides by high power visible light direct photoactivation RAFT polymerisation
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C7PY01752A
Abstract: The effect of visible LED power ( λ max = 402 nm, 451 nm) on kinetics and control of direct photoactivation RAFT polymerisations of acrylamide and dimethylacrylamide are investigated.
Self-Organized Monolayer Films of Stimulus-Responsive Micelles
Publisher: American Chemical Society (ACS)
Date: 24-10-2002
DOI: 10.1021/NL025781B
A quantum chemical molecular dynamics repository of solvated ions
Publisher: Springer Science and Business Media LLC
Date: 21-07-2022
DOI: 10.1038/S41597-022-01527-8
Abstract: The importance of ion-solvent interactions in predicting specific ion effects in contexts ranging from viral activity through to electrolyte viscosity cannot be underestimated. Moreover, investigations of specific ion effects in nonaqueous systems, highly relevant to battery technologies, biochemical systems and colloid science, are severely limited by data deficiency. Here, we report IonSolvR – a collection of more than 3,000 distinct nanosecond-scale ab initio molecular dynamics simulations of ions in aqueous and non-aqueous solvent environments at varying effective concentrations. Density functional tight binding (DFTB) is used to detail the solvation structure of up to 55 solutes in 28 different protic and aprotic solvents. DFTB is a fast quantum chemical method, and as such enables us to bridge the gap between efficient computational scaling and maintaining accuracy, while using an internally-consistent simulation technique. We validate the database against experimental data and provide guidance for accessing in idual IonSolvR records.
Effects of copolymer concentration and chain length on the pH-responsive behavior of diblock copolymer micellar films
Publisher: Elsevier BV
Date: 11-2006
DOI: 10.1016/J.JCIS.2006.07.077
Abstract: The pH-responsive behavior of adsorbed diblock copolymer films of PDMA-PDEA (poly(2-(dimethylamino)ethyl methacrylate)-block-poly(2-(diethylamino)ethyl methacrylate)) on silica has been characterized using a quartz crystal microbalance with dissipation monitoring (QCM-D), an optical reflectometer (OR) and an atomic force microscope (AFM). The copolymer was adsorbed at pH 9 from various copolymer concentrations QCM-D measurements indicate that the level of desorption when rinsed at pH 9 depends on the initial copolymer concentration. The adsorbed films produced at pH 9 generally have low charge densities adjusting the solution pH to 4 results in a significant protonation of the constituent copolymers and a related interfacial structural change for the copolymer film. OR studies show no significant change during pH cycling, while QCM-D measurements indicate that the adsorbed mass and dissipation alter dramatically in response to the solution pH. The difference between the QCM-D adsorbed masses and dissipation values at pH 4 and 9 were found to be dependent on the initial copolymer concentration. This is due to differences in the initial conformations within the adsorbed copolymer layers at pH 9. The effect of the PDMA chain length on the pH-responsive behavior has also been studied both the QCM-D adsorbed mass and dissipation of PDMA54-PDEA24 (shorter PDMA block) at pH 4 and 9 were observed to be greater than those of PDMA9X-PDEA2Y (longer PDMA block). This suggests that the normal extension of the adsorbed PDMA54-PDEA24 copolymer films is more significant than that of the PDMA9X-PDEA2Y films on silica.
A standardised approach for determining heat tolerance in cotton using triphenyl tetrazolium chloride
Publisher: Springer Science and Business Media LLC
Date: 08-03-2021
DOI: 10.1038/S41598-021-84798-2
Abstract: Improving the heat tolerance of cotton is a major concern for breeding programs. To address this need, a fast and effect way of quantifying thermotolerant phenotypes is required. Triphenyl tetrazolium chloride (TTC) based enzyme viability testing following high-temperature stress can be used as a vegetative heat tolerance phenotype. This is because when live cells encounter a TTC solution, TTC undergoes a chemical reduction producing a visible, insoluble red product called triphenyl formazan, that can be quantified spectrophotometrically. However, existing TTC based cell viability assays cannot easily be deployed at the scale required in a crop improvement program. In this study, a heat stress assay (HSA) based on the use of TTC enzyme viability testing has been refined and improved for efficiency, reliability, and ease of use through four experiments. S ling factors that may influence assay results, such as leaf age, plant water status, and short-term cold storage, were also investigated. Experiments conducted in this study have successfully downscaled the assay and identified an optimal s ling regime, enabling measurement of large segregating populations for application in breeding programs. The improved HSA methodology is important as it is proposed that long-term improvements in cotton thermotolerance can be achieved through the concurrent selection of superior phenotypes based on the HSA and yield performance in hot environments. Additionally, a new way of interpreting both heat tolerance and heat resistance was developed, differentiating genotypes that perform well at the time of a heat stress event and those that maintain a similar performance level to a non-stressed control.
Lattice-resolution imaging of the sapphire (0 0 0 1) surface in air by AFM
Publisher: Elsevier BV
Date: 02-2007
Geometrical Confinement Modulates the Thermoresponse of a Poly(N-isopropylacrylamide) Brush
Publisher: American Chemical Society (ACS)
Date: 23-02-2021
Optimized peptide functionalization of thiol‐acrylate emulsion‐templated porous polymers leads to expansion of human pluripotent stem cells in 3D culture
Publisher: Wiley
Date: 09-03-2019
DOI: 10.1002/POLA.29353
Influence of polymer charge on the shear yield stress of silica aggregated with adsorbed cationic polymers
Publisher: Elsevier BV
Date: 08-2009
DOI: 10.1016/J.JCIS.2009.04.027
Abstract: Flocs were produced by adding three cationic polymers (10% charge density, 3.0x10(5) g/mol molecular weight 40% charge density, 1.1x10(5) g/mol molecular weight and 100% charge density, 1.2x10(5) g/mol molecular weight) to 90 nm diameter silica particles. The shear yield stresses of the consolidated sediment beds from settled and centrifuged flocs were determined via the vane technique. The polymer charge density plays an important role in influencing the shear yield stresses of sediment beds. The shear yield stresses of sediment beds from flocs induced by the 10% charged polymer were observed to increase with an increase in polymer dose, initial solid concentration and background electrolyte concentration at all volume fractions. In comparison, polymer dose has a marginal effect on the shear yield stresses of sediment beds from flocs induced by the 40% and 100% charged polymers. The shear yield stresses of sediments from flocs induced by the 40% charged polymer are independent of salt concentration whereas the addition of salt decreases the shear yield stresses of sediments from flocs induced by the 100% charged polymer. When flocculated at the optimum dose for each polymer (12 mg/g silica for the 10% charged polymer at 0.03 M NaCl, 12 mg/g for 40% and 2 mg/g for 100%), shear yield stress increases as polymer charge increases. The effects observed are related to the flocculation mechanism (bridging, patch attraction or charge neutralisation) and the magnitude of the adhesive force. Comparison of shear and compressive yield stresses show that the network is only slightly weaker in shear than in compression. This is different than many other systems (mainly salt and pH coagulation) which have shear yield stress much less than compressive yield stress. The existing models relating the power law exponent of the volume fraction dependence of the shear yield stress to the network fractal structure are not satisfactory to predict all the experimental behaviour.
Specific ion effects on thermoresponsive polymer brushes: Comparison to other architectures
Publisher: Elsevier BV
Date: 09-2018
DOI: 10.1016/J.JCIS.2018.04.086
Abstract: Thermoresponsive polymers have received significant research attention as smart materials with particular interest in biomedical applications. The composition and architecture are known to strongly influence the thermoresponsive properties of the materials. For ex le, the strong overlap of end-grafted polymer chains in polymer brushes leads to a broader collapse transition relative to linear ungrafted chains as well as temperature dependent adhesion. The temperature response of free polymer has been widely reported to depend on the concentration and identity of ions in solution and is further modified by the composition of the solvent and presence of cosolutes. However, the influence of polymer architecture on these specific ion effects is relatively unknown. Herein, we compare the current understanding of specific ion effects on free polymer chains and gels with recent studies of polymer brushes. Further studies on mixed salt systems are found to be the next step to predicting the behaviour of these materials in biological systems.
Solubility of calcium sulfate salts in acidic manganese sulfate solutions from 30 to 105 °C
Publisher: Elsevier BV
Date: 04-2007
Temperature dependent specific ion effects in mixed salt environments on a thermoresponsive poly(oligoethylene glycol methacrylate) brush
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C8CP06644B
Abstract: The temperature induced swelling/collapse transition of poly(oligoethylene glycol methacrylate) (POEGMA) brushes has been investigated in electrolyte solutions comprised of multiple anions.
The effect of ionic surfactant adsorption on the rheology of ceramic glaze suspensions
Publisher: Wiley
Date: 03-2005
Non-ionic surfactant interactions with hydrophobic nanoparticles: Impact on foam stability
Publisher: Elsevier BV
Date: 09-2009
Specific ion modulated thermoresponse of poly(N-isopropylacrylamide) brushes
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C5CP07468A
Abstract: Specific anion identity and concentration dictates the direction and magnitude of the shift in LCST for a pNIPAM brush determined by in situ ellipsometry, QCM-D and static contact angle measurements.
Film-Forming Microgels for pH-Triggered Capture and Release
Publisher: American Chemical Society (ACS)
Date: 19-08-2008
DOI: 10.1021/LA8017425
Abstract: The pH-responsive behavior for a series of lightly cross-linked, sterically stabilized poly(tertiary amine methacrylate)-based latexes adsorbed onto mica and silica was investigated using in situ tapping mode AFM at room temperature. The adsorbed layer structure was primarily determined by the glass transition temperature, T(g), of the latex: poly[2-(diethylamino)ethyl methacrylate]-based particles coalesced to form relatively featureless uniform thin films, whereas the higher T(g) poly[2-(diisopropylamino)ethyl methacrylate] latexes retained their original particulate character. Adsorption was enhanced by using a cationic poly[2-(dimethylamino)ethyl methacrylate] steric stabilizer, rather than a nonionic poly(ethylene glycol)-based stabilizer, since the former led to stronger electrostatic binding to the oppositely charged substrate. Both types of adsorbed latexes acquired cationic microgel character and swelled appreciably at low pH, even those that had coalesced to form films. Fluorescence spectroscopy was used to study the capture of a model hydrophobic probe, pyrene, by these adsorbed latex layers followed by its subsequent release by lowering the solution pH. The repeated capture and release of pyrene through several pH cycles was also demonstrated. Since these poly(tertiary amine methacrylate) latexes are readily prepared by aqueous emulsion polymerization and adsorption occurs spontaneously from aqueous solution, this may constitute an attractive route for the surface modification of silica, mica and other oxides.
Crystalline and Hairy Nanocelluloses for 3D Printed Hydrogels and Strongly Structured Cryogels
Publisher: American Chemical Society (ACS)
Date: 28-03-2023
Advances and Challenges in the Design and Synthesis of Molecularly Imprinted Microspheres
Publisher: Elsevier
Date: 2016
Controlling pickering emulsion destabilisation: A route to fabricating new materials by phase inversion
Publisher: MDPI AG
Date: 27-07-2016
DOI: 10.3390/MA9080626
An Electrostatic Method for Manufacturing Liquid Marbles and Particle-Stabilized Aggregates
Publisher: Frontiers Media SA
Date: 10-07-2018
Modelling the Motion of a Collected Particle over a Bubble Surface
Publisher: Elsevier BV
Date: 2015
Prospects for Cherenkov Telescope Array Observations of the Young Supernova Remnant RX J1713.7-3946
Publisher: American Astronomical Society
Date: 09-05-2017
Synthesis of UHMW Star-Shaped AB Block Copolymers and Their Flocculation Efficiency in High-Ionic-Strength Environments
Publisher: American Chemical Society (ACS)
Date: 02-10-2019
Influence of Anion Hydrophilicity on the Conformation of a Hydrophobic Weak Polyelectrolyte Brush
Publisher: American Chemical Society (ACS)
Date: 13-12-2016
Electrostatic Transfer of Conductive Particles for the Formation of Liquid Marbles–Charge Transfer Behavior
Publisher: American Chemical Society (ACS)
Date: 14-04-2020
Surface aggregate phase transition
Publisher: American Chemical Society (ACS)
Date: 08-1997
DOI: 10.1021/LA970146K
Effect of morphology on interactions between nanoparticle-stabilised air bubbles and oil droplets
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C7SM02280H
Abstract: Adsorbed copolymer nanoparticle spheres and worms can stabilise oil droplet or air bubble pairs, or indeed multiphase systems.
Bioceramic nanocomposite thiol-acrylate polyHIPE scaffolds for enhanced osteoblastic cell culture in 3D
Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7BM00292K
Abstract: Addition of bioceramics to emulsion-templated scaffolds greatly enhances ostoeblastic cell proliferation and promotes early mineralisation.
The transition to first year chemistry: student, secondary and tertiary educator's perceptions of student preparedness
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1RP00068C
Abstract: Student preparedness is an essential component of transition to university influenced by a broad suite of attributes including academic aptitude, prior knowledge, self-efficacy, self-confidence and a complex assortment of study and life skills. In the case of chemistry education, students' self-perceptions of preparedness are intrinsically linked to prior learning of both theory and hands on laboratory experiences, and interwoven with intricacies such as science identity, gender, and secondary school background. Accordingly, this study sought to establish a deeper understanding of learners' and educators' perceptions of student preparedness upon commencing tertiary studies in chemistry. The research used a mixed methods approach including questionnaires, focus groups, and interviews to capture the breadth and depth of these perceptions. 924 students from the first year chemistry cohort completed either one or two surveys designed to capture their prospective and retrospective self-perceptions of how well prepared they were for the course. Nine of these students also participated in focus groups. Secondary educator's views were captured via a qualitative online survey to conveniently enable a broad cohort to be s led, while tertiary educators from the institution where this study was conducted were interviewed in person. Key findings from students include: a strong correlation between self-perception of preparedness and academic performance, those with negative perceptions of preparedness are genuinely an at-risk category, an overall positive shift for perceptions of preparedness for students as they get to the end of the semester (which is more pronounced for students who attended private secondary schools), and a significant disparity between genders at the start of the semester that was no longer present by the end. Additional key findings include the disparity between secondary and tertiary educator's perspectives of how well prepared students are for the transition to tertiary level chemistry studies. While the former have a favourable view, the latter consider many students to be quite poorly prepared, with each cohort ultimately focusing on different attributes. We suggest the implications for these findings include the importance of emphasising expectations of students as they commence their courses, and that work still needs to be done to align the perspectives of educators at all levels when it comes to preparing and supporting students as they transition to higher education.
Three-dimensional differentiation of human pluripotent stem cell-derived neural precursor cells using tailored porous polymer scaffolds
Publisher: Elsevier BV
Date: 2020
DOI: 10.1016/J.ACTBIO.2019.10.017
Abstract: This study investigates the utility of a tailored poly(ethylene glycol) diacrylate-crosslinked porous polymeric tissue engineering scaffold, with mechanical properties specifically optimised to be comparable to that of mammalian brain tissue for 3D human neural cell culture. Results obtained here demonstrate the attachment, proliferation and terminal differentiation of both human induced pluripotent stem cell- and embryonic stem cell-derived neural precursor cells (hPSC-NPCs) throughout the interconnected porous network within laminin-coated scaffolds. Phenotypic data and functional analyses are presented demonstrating that this material supports terminal in vitro neural differentiation of hPSC-NPCs to a mixed population of viable neuronal and glial cells for periods of up to 49 days. This is evidenced by the upregulation of TUBB3, MAP2, SYP and GFAP gene expression, as well as the presence of the proteins βIII-TUBULIN, NEUN, MAP2 and GFAP. Functional maturity of neural cells following 49 days 3D differentiation culture was tested via measurement of intracellular calcium. These analyses revealed spontaneously active, synchronous and rhythmic calcium flux, as well as response to the neurotransmitter glutamate. This tailored construct has potential application as an improved in vitro human neurogenesis model with utility in platform drug discovery programs. STATEMENT OF SIGNIFICANCE: The interconnected porosity of polyHIPE scaffolds exhibits the ability to support three-dimensional neural cell network formation due to limited resistance to cellular migration and re-organisation. The previously developed scaffold material displays mechanical properties similar to that of the mammalian brain. This research also employs the utility of pluripotent stem cell-derived neural cells which are of greater clinical relevance than primary neural cell lines. This scaffold material has future potential in better mimicking three-dimensional neural networks found in the human brain and may result in improved in vitro models for disease modelling and drug screening applications.
Polyelectrolyte brush pH-response at the silica–aqueous solution interface: a kinetic and equilibrium investigation
Publisher: Royal Society of Chemistry (RSC)
Date: 2013
DOI: 10.1039/C3CP52281D
Abstract: Polymer brushes are commonly used to modify the properties of solid surfaces. Here a family of polybasic poly(2-(diethylamino)ethyl methacrylate) brushes have been grown using ARGET ATRP from a cationic macroinitiator adsorbed on two types of silica surfaces: QCM crystals and oxidised silicon wafers. The pH-response of these brushes is investigated as a function of brush thickness in a constant flow environment in order to focus on the intrinsic dynamics of the polymer brushes. Independent QCM-D and in situ ellipsometry kinetic studies demonstrate the swelling process of protonation and solvent uptake is typically eight times faster than the corresponding neutralisation and solvent expulsion from the collapsing brush. However, the maximum rate of these processes is independent of brush thickness. The initial pH response of the brushes is hysteretic due to brush entanglement, which once overcome allows highly reversible pH-induced conformational changes. Multiple pH cycles demonstrate that the viscoelastic nature of the swollen state relative to the collapsed brush is independent of brush thickness.
Critical salt effects in the swelling behavior of a weak polybasic brush
Publisher: American Chemical Society (ACS)
Date: 10-02-2014
DOI: 10.1021/LA4047275
Abstract: The swelling behavior of poly(2-(diethylamino)ethyl methacrylate) (PDEA) brushes in response to changes in solution pH and ionic strength has been investigated. The brushes were synthesized by ARGET ATRP methodology at the silica-aqueous solution interface via two different surface-bound initiator approaches: electrostatically adsorbed cationic macroinitiator and covalently anchored silane-based ATRP initiator moieties. The pH-response of these brushes is studied as a function of the solvated brush thickness in a constant flow regime that elucidates the intrinsic behavior of polymer brushes. In situ ellipsometry equilibrium measurements show the pH-induced brush swelling and collapse transitions are hysteretic in nature. Furthermore, high temporal resolution kinetic studies demonstrate that protonation and solvent ingress during swelling occur much faster than the brush charge neutralization and solvent expulsion during collapse. This hysteresis is attributed to the formation of a dense outer region or skin during collapse that retards solvent egress. Moreover, at a constant pH below its pKa, the PDEA brush exhibited a critical conformational change in the range 0.5-1 mM electrolyte, a range much narrower than predicted by the theory of the osmotic brush regime. This behavior is attributed to the hydrophobicity of the collapsed brush. The swelling and collapse kinetics for this salt-induced transition are nearly identical. This is in contrast to the asymmetry in the rate of the pH-induced response, suggesting an alternative mechanism for the two processes dependent on the nature of the environmental trigger.
Organization of Sodium Dodecyl Sulfate at the Graphite−Solution Interface
Publisher: American Chemical Society (ACS)
Date: 1996
DOI: 10.1021/JP952439X
Influence of particle size on extraction from a charged bed – toward liquid marble formation
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9SM01467E
Abstract: Larger particles are more readily extracted from an advancing bed of charged particles owing to decreased interparticle cohesion.
Effect of ionic strength and salt identity on poly(N-isopropylacrylamide) brush modified colloidal silica particles
Publisher: Elsevier BV
Date: 04-2018
DOI: 10.1016/J.JCIS.2018.01.058
Abstract: The thermoresponse of poly(N-isopropylacrylamide) stabilised particles is influenced by the presence of salt and is dependent on the concentration, and ions present. The conformation and electrophoretic mobility of core/shell PNIPAM brush modified silica particles is expected to vary as a function of these specific ion effects. The thermoresponse of PNIPAM brush modified silica particles was investigated via dynamic light scattering and electrophoretic mobility measurements between 5 and 45 °C in the presence of 11 different salt solutions. Specific ion effects were observed in the presence of salt solutions for concentrations between 50 and 1000 mM. The temperature response could be mapped to a master curve unlike PNIPAM brush behaviour on planar substrates. The magnitude of brush layer lower critical solution temperature reduction was found to follow the order F
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End Date: 12-2016
Amount: $200,000.00
Funder: Australian Research Council
View Funded ActivityARC Centres Of Excellence - Grant ID: CE200100009
Start Date: 07-2020
End Date: 07-2027
Amount: $35,000,000.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP0555908
Start Date: 04-2005
End Date: 04-2009
Amount: $225,000.00
Funder: Australian Research Council
View Funded Activity