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Polystyrene Latex Particles (polystyrene + latex_particle)
Selected AbstractsElectrode Reactions of Catechol at Tyrosinase-Immobilized Latex SuspensionsELECTROANALYSIS, Issue 8 2004Patsamon Rijiravanich Abstract Tyrosinase was immobilized on polystyrene latex particles in order to control amounts of the enzyme. The tyrosinase-coated latex particles were composed of the core polystyrene and four successive coating layers: polystyrene sulfonate, polyallylamine, tyrosinase and polyallylamine again, built up by the layer-by-layer technique. They showed catalytic currents for the enzymatic oxidation of catechol to o -quinone. The enzyme activity per particle was evaluated as 2.3×10,7 units from UV absorption of o -quinone. The relation between the catalytic current and the concentration of catechol leads to a Michaelis-Menten type kinetic equation. The layer-by-layer method was found to have a deactivating effect on enzyme catalysis. In spite of this, the catechol oxidation current was larger than the current from free tyrosinase at a common value of enzyme units per volume. This is ascribed to strong adsorption of the latex particles on the electrode, leading to the enhancement of the local concentration of tyrosinase. [source] Highly magnetic latexes from submicrometer oil in water ferrofluid emulsionsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2006Franck Montagne Abstract The synthesis of functionalized submicrometer magnetic latex particles is described as obtained from a preformed magnetic emulsion composed of organic ferrofluid droplets dispersed in water. Composite (polystyrene/,-Fe2O3) particles were prepared according to a two-step procedure including the swelling of ferrofluid droplets with styrene and a crosslinking agent (divinyl benzene) followed by seeded emulsion polymerization with either an oil-soluble [2,2,-azobis(2-isobutyronitrile)] or water-soluble (potassium persulfate) initiator. Depending on the polymerization conditions, various particle morphologies were obtained, ranging from asymmetric structures, for which the polymer phase was separated from the inorganic magnetic phase, to regular core,shell morphologies showing a homogeneous encapsulation of the magnetic pigment by a crosslinked polymeric shell. The magnetic latexes were extensively characterized to determine their colloidal and magnetic properties. The desired core,shell structure was efficiently achieved with a given styrene/divinyl benzene ratio, potassium persulfate as the initiator, and an amphiphilic functional copolymer as the ferrofluid droplet stabilizer. Under these conditions, ferrofluid droplets were successfully turned into superparamagnetic polystyrene latex particles, about 200 nm in size, containing a large amount of iron oxide (60 wt %) and bearing carboxylic surface charges. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2642,2656, 2006 [source] Determination of the extent of incorporation of a reactive surfactant in polystyrene latex particles via GPCJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2005Zhen Lai The reactive surfactant HITENOL BC20 (polyoxyethylene alkylphenyl ether ammonium sulfate containing 20 units of ethylene oxide) was used in emulsion polymerizations of styrene with potassium persulfate as initiator. A new method to determine the amount of chemically bound surfactant was developed using GPC combined with UV detection as shown in the figure. Comparing this GPC method with the serum replacement/FTIR method reveals it to be a relatively simple and more effective means of characterization. [source] Surfactant characteristics of polystyrene/poly(ethylene oxide) macromonomers in aqueous solution and on polystyrene latex particles: Two-step emulsion polymerizationsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2001Sebastien Gibanel Abstract Macromonomers were synthesized by anionic "living" polymerization. They comprised a poly(ethylene oxide) hydrophilic block and a hydrophobic block or sequence terminated with an unsaturation. The surface activity properties of these materials (critical micelle concentration and parking area) were determined, and the values were compared and discussed in terms of the molecular structure of these new surfactants. Some of the macromonomers were employed as emulsifiers in two-step emulsion polymerizations. The data obtained were discussed while taking into account the different chemical structures of the macromonomers and the efficiency of these species as emulsifiers in the polymerization recipes. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2767,2776, 2001 [source] Initial Deposition of Colloidal Particles on a Rough Nanofiltration MembraneTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2007Tania Rizwan Abstract The initial rate of colloid deposition onto semi-permeable membranes is largely controlled by the coupled influence of permeation drag and particle-membrane colloidal interactions. Recent studies show that the particle-membrane interactions are subject to immense local variations due to the inherent morphological heterogeneity (roughness) of reverse osmosis (RO) and nanofiltration (NF) membranes. This experimental investigation reports the effect of membrane roughness on the initial deposition of polystyrene latex particles on a rough NF membrane during cross flow membrane filtration under different operating pressures and solution chemistries. Atomic force microscopy was used to characterize the roughness of the membrane and observe the structure of particle deposits. At the initial stages of fouling, the AFM images show that more particles preferentially accumulate near the "peaks" than in the "valleys" of the rough NF membrane surface. Le taux initial de la déposition colloïdale sur des membranes semi-perméables est largement contrôlé par l'influence couplée entre la traînée de perméation et les interactions colloïdales membrane-particules. Des études récentes montrent que les interactions membranes-particules sont sujettes à d'immenses variations locales en raison de l'hétérogénéité morphologique inhérente (rugosité) des membranes d'osmose inverse (RO) et de nanofiltration (NF). Cette étude expérimentale décrit l'effet de la rugosité des membranes sur la déposition initiale de particules de latex de polystyrène sur une membrane NF rugueuse lors de la filtration des membranes en écoulement transversal pour différentes conditions opératoires et compositions chimiques des solutions. On a eu recours à la microscopie à force atomique pour caractériser la rugosité de la membrane et observer la structure des dépôts de particules. Aux stades initiaux du refoulement, les images AFM montrent que les particules s'accumulent préférentiellement près des «pics» plutôt que dans les «vallées» de la surface de membrane NF rugueuse. [source] Molecular-scale investigation of polymerization, nucleation, and growth of polystyrene particle by atomic force microscopyASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2008Tetsuya Yamamoto Abstract To clarify the mechanism of the nucleation and growth processes in the soap-free polymerization of polystyrene latex particles in water, the polymerization process was investigated on a molecular scale, by using an atomic force microscope (AFM), as well as a scanning electron microscope (SEM) and a dynamic light scattering apparatus (DLS). A ,cationic' initiator was employed to make all the polymeric materials produced, such as oligomers, embryos, nuclei, and grown particles, adsorb electrostatically on the negatively charged mica plate of molecular-scale smoothness. This in situ transfer of polymeric materials in the bulk onto the mica surface enables us to observe the images of polymeric materials during the reaction process and to estimate what is happening in the nucleation and growth processes of particles, at least qualitatively. The most important findings of the present study are that1 these molecular-scale polymeric materials, to which much attention has not been paid probably because of the difficulty of detection, are continuously born in the bulk throughout the reaction process of particle formation, and2 they play an important role in the growth of particles. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source] | ||||||||||