3,119 research outputs found
Microgel particles as model colloids: theory, properties and applications
No full textBrian R. Saunders, Brian Vincen
Poly(NIPAM) microgel particle de-swelling: a light scattering and small-angle neutron scattering study
No full textHelen M Crowther, Brian R Saunders, Sarah J Mears, Terence Cosgrove, Brian Vincent, Stephen M King, Ga-Er Y
Competition policy. by Brian Ellis
No full texttag=1 data=Competition policy. by Brian Ellis
tag=2 data=Ellis, Brian
tag=3 data=Australian Rationalist,
tag=5 data=46
tag=6 data=Autumn/Winter 1998
tag=7 data=51-56.
tag=8 data=ECONOMIC CONDITIONS
tag=9 data=COMPETITION%CORPORATISATION%NATIONAL COMPETITION POLICY%PRIVATE SECTOR PUBLIC SECTOR EFFECTIVENESS%SERVICE DELIVERY%SOCIAL POLICY%INNOVATION
tag=10 data=Examines the Government's National Competition Policy in relation to encouraging R&D, and the corporisation of public services and utilites. The author is Emeritus Professor of Philosophy at La Trobe UNiversity and Vice-President of the Rationalist Society of Australia. Article Taken from What's New.
tag=13 data=CABExamines the Government's National Competition Policy in relation to encouraging R&D, and the corporisation of public services and utilites. The author is Emeritus Professor of Philosophy at La Trobe UNiversity and Vice-President of the Rationalist Society of Australia. Article Taken from What's New
One-step preparation of uniform cane-ball shaped water-swellable microgels containing poly(N-vinyl formamide)
No full textIn this study we report the preparation of a new family of core shell microgels that are water-swellable and have a morphology that is controllable by particle composition. Here, nearly monodisperse core shell PNVF-xGMA [poly(N-vinylformamide-co-glycidyl methacrylate)] particles (where x is the weight fraction of GMA used) were prepared via nonaqueous dispersion (NAD) polymerization in one step. The shells were PGMA-rich and were cross-linked by reaction of epoxide groups (from GMA) with amide groups (from NVF). The core of the particles was PNVF-rich. A bifunctional cross-linking monomer was not required to prepare these new microgels. The particles had a remarkable "cane-ball"-like morphology with interconnected ridges, and this could be controlled by the value for x. The particle size was tunable over the range 0.8-1.8 mu m Alkaline hydrolysis was used to hydrolyze the PNVF segments to poly(vinylamine), PVAM. The high swelling pressure of the cationic cores caused shell fragmentation and release of some of the core polymer when the hydrolyzed particles were dispersed in pure water. The extent to which this occurred was controllable by x. Remarkably, the PGMA-rich shells could be detached from the hydrolyzed particles by dispersion in water followed by drying. The hydrolyzed PNVF-0.4GMA particles contained both positively and negatively charged regions and the dispersions appeared to exhibit charge-patch aggregation at low ionic strengths. The new cross-linking strategy used here to prepare the PNVF-xGMA particles should be generally applicable for amide-containing monomers and may enable the preparation of a range of new water-swellable microgels
Colloidal thermoresponsive gel forming hybrids
No full textColloidal hybrids comprise organic and inorganic components and are attracting considerable attention in the literature. Recently, we reported hybrid anisotropic microsheets that formed thermoresponsive gels in polymer solutions [Liu et al., Langmuir, 25, 490, 2009]. Here, we investigate the composition and properties of these hybrid colloids themselves in detail for the first time. Three different cationic PNIPAm (N-isopropylacrylamide) graft copolymers and two inorganic nanoparticle types (laponite and Ludox silica) were used to prepare a range of hybrids. Anisotropic microsheets only formed when laponite particles were added to the copolymer implying directed self-assembly. Aqueous dispersions of the microsheets spontaneously formed gels at room temperature and these gels were thermoresponsive. They represent a new class of gel forming colloid and are termed thermoresponsive gel forming hybrids. The compositions of the hybrids were determined from thermogravimetric analysis and those that gave gel forming behaviour identified. Variable-temperature rheology experiments showed that the elasticity of the gels increased linearly with temperature. The reversibility of the thermally-triggered changes in gel elasticity was investigated. The concentration dependence of the rheology data was well described by elastic percolation scaling theory and the data could be collapsed onto a master curve. The concentration exponent for the elastic modulus was 2.5. The strong attractive interactions that exist between the dispersed gel forming hybrids was demonstrated by the formation of stable thermoresponsive hybrid hydrogels through casting of hybrid dispersions. © 2010 Elsevier Inc
pH-responsive microgels containing hydrophilic crosslinking co-monomers: shell-exploding microgels through design
No full textpH-responsive microgels are crosslinked polymer colloids that swell when the pH approaches the pKa of the particles. They have potential application for injectable gels for tissue repair and drug delivery systems. This study focuses on the pH-triggered gelation behaviour of a series of poly (EA/MAA/X) microgels. EA and MAA are ethylacrylate and methacrylic acid. Here, we investigate the effect of crosslinking monomer type (X) on microgel properties. The crosslinking monomers used were poly (ethyleneglycol) dimethacrylate (PEGD), ethyleneglycol dimethacrylate (EGD) and butanediol diacrylate (BDD). The microgel containing PEGD (m-PEGD) is a new system. The microgel containing BDD (m-BDD) was used as a control system. The concentrated microgel dispersions formed physical gels when the pH was increased to 5.3-6.7, and the polymer volume fractions (φp) were above about 0.05. Evidence from photon correlation spectroscopy (PCS) and dynamic rheology was presented for abrupt pH-triggered increases, and then decreases of the hydrodynamic diameters for m-PEGD and the microgel prepared using EGD (m-EGD). This appears to be tuneable through crosslinker structure. An unexpected gelation behaviour, which may involve a new gel state for microgels, was found for m-PEGD dispersions. Uniquely, those dispersions formed gels at pH values less than the microgel's pKa. This behaviour was linked to an outer-shell electrostatic repulsive interaction. The data point to a phenomenon, whereby the m-PEGD shells appear to explode at pH values above 7.0. The control microgel prepared, using BDD (m-BDD), did not show any evidence of shell fragmentation at any pH. That microgel has potential as a model pH-responsive microgel system in that the properties measured by PCS and rheology agreed well. To probe that system in more detail, the rheological data for m-BDD was analysed using scaling theory. The variation of the storage modulus (G′) with φp gave a scaling exponent of 2.0. © Springer-Verlag 2011
A creaming study of weakly flocculated and depletion flocculated oil-in-water emulsions
No full textMichael Shields, Robert Ellis, Brian R Saunder
Thermally Triggered Assembly of Cationic Graft Copolymers Containing 2-(2-Methoxyethoxy)ethyl Methacrylate Side Chains
No full textThermoresponsive copolymers continue to attract a great deal of interest in the literature. In particular, those based on ethylene oxide-containing methacrylates have excellent potential for biomaterial applications. Recently, some of us reported a study of thermoresponsive cationic graft copolymers containing poly(N-isopropylacrylamide), PNIPAm, (Liu et al., Langmuir, 24, 7099). Here, we report an improved version of this new family of copolymers. In the present study, we replaced the PNIPAm side chains with poly(2-(2- methyoxyethoxy)ethylmethacrylate), PMeO 2MA. These new, nonacrylamide containing, cationic graft copolymers were prepared using atom transfer radical polymerization (ATRP) and a macroinitiator. They contained poly(trimethylamonium)-aminoethyl methacrylate and PMeO 2MA, i.e., PTMA + x-g-(PMeO 2MA n) y. They were investigated using variable-temperature turbidity, photon correlation spectroscopy (PCS), electrophoretic mobility, and 1H NMR measurements. For one system, four critical temperatures were measured and used to propose a mechanism for the thermally triggered changes that occur in solution. All of the copolymers existed as unimolecular micelles at 20 °C. They underwent reversible aggregation with heating. The extent of aggregation was controlled by the length of the side chains. TEM showed evidence of micellar aggregates. The thermally responsive behaviors of our new copolymers are compared to those for the cationic PNIPAm graft copolymers reported by Liu et al. Our new cationic copolymers retained their positive charge at all temperatures studied, have high zeta potentials at 37 °C, and are good candidates for conferring thermoresponsiveness to negatively charged biomaterial surfaces. © 2011 American Chemical Society
Calculation of muscle maximal shortening velocity by extrapolation of the force-velocity relationship: Afterloaded versus isotonic release contractions
No full textSource type: Electronic(1
A web-based screening tool for near-port air quality assessments
Full text linkAuthor(s): Isakov, Vlad; Barzyk, Timothy M; Smith, Elizabeth R; Arunachalam, Saravanan; Naess, Brian; Venkatram, Akul
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