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Polymer Particles (polymer + particle)
Selected AbstractsChemical Nanosensors Based on Composite Molecularly Imprinted Polymer Particles and Surface-Enhanced Raman ScatteringADVANCED MATERIALS, Issue 21 2010Marc Bompart Chemical nanosensors with a submicrometer core,shell composite design, based on a polymer core, a molecularly imprinted polymer (MIP) shell for specific analyte recognition, and an interlayer of gold nanoparticles for signal amplification, are described. SERS measurements on single nanosensors yield detection limits of 10,7,M for the , -blocker propranolol, several orders of magnitude lower than on plain MIP spheres. [source] Morphology-Selective Formation and Morphology-Dependent Gas-Adsorption Properties of Coordination Polymer ParticlesADVANCED MATERIALS, Issue 6 2009Hee Jung Lee Three coordination polymer particles (CPPs) are selectively synthesized using the solvothermal method. All three CPPs are prepared from the same building blocks. However, they form different morphologies, such as elongated hexagons, ellipsoids, and rods. Gas-adsorption measurements on N2, CO2, and H2 reveal that diversely shaped CPPs have different gas-adsorption properties, even though they have the same chemical compositions. [source] One-Pot Fabrication of Supramolecular Polymer Particles via Situ Polymerization Stringed Assembly of a Two-Monomer MicroemulsionMACROMOLECULAR RAPID COMMUNICATIONS, Issue 4 2006Yongxin Wang Abstract Summary: A novel method, situ polymerization stringed assembly (SPSA), is proposed to prepare stable solid or hollow supramolecular polymer particles, which are assembled by numerous nanoparticles. By this method, the fabrication of primary nanoparticles (poly(methyl methacrylate), PMMA), the linkers (polyvinylpyrrolidone, PVP, chains) between the nanoparticles, and the final assembled solid or hollow particles could be achieved in just one-pot by methyl methacrylate (MMA)/N -vinylpyrrolidone (NVP) microemulsion polymerization under UV irradiation. The structures of the supramolecular particles can be changed from solid to hollow by tuning the mass ratio of MMA/NVP in the microemulsion. AFM, TEM, and SEM experiments are performed to identify the results. AFM image of the PMMA/PVP solid particles obtained from the photopolymerization of the microemulsion containing 20 wt.-% MMA, 10 wt.-% NVP, and 5,×,10,2 wt.-% BP. [source] Metal Nanoparticle/Polymer Hybrid Particles: The Catalytic Activity of Metal Nanoparticles Formed on the Surface of Polymer Particles by UV-IrradiationMACROMOLECULAR SYMPOSIA, Issue 1 2009Toshiyuki Tamai Abstract Summary: Polymer particles decorated with metal nanoparticles were prepared by UV-irradiation of polystyrene particles incorporating polymethylphenylsilane (PS/PMPS) and P[S- co -NIPAM]/PMPS particles (NIPAM: N-isopropyl acrylamide) in the presence of metal salts. The metal nanoparticle/polymer hybrid particles were used as a catalyst for the reduction of 4-nitrophenol with NaBH4. The Pd- and Ag-P(S- co -NIPAM)/PMPS hybrid particles had larger metal nanoparticles and the lower catalytic activity than those of Pd- and Ag-PS/PMPS, respectively. The surface functional group of the polymer particles affected the formation of the metal nanoparticles and their catalytic activity. [source] Spatially Resolved Catalysis for Controlling the Morphology of Polymer Particles,ANGEWANDTE CHEMIE, Issue 35 2009Till Diesing Zwei in einem: Ein Replikationseffekt ermöglicht die Bildung von Kern-Schale-Partikeln in einem einzigen Olefinpolymerisationsschritt durch simultanes Nutzen räumlich getrennter Metallocenkatalysatoren, die auf einem anorganisch-organischen Träger immobilisiert sind (siehe Bild). Katalysator,A befand sich ausschließlich im anorganischen Kern, Katalysator,B dagegen in der organischen Schale. [source] Microfluidic-Assisted Synthesis of Polymer ParticlesCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 8 2008A. Serra Abstract Microfluidic devices have recently emerged as promising tools for the synthesis of polymer particles. Over conventional processes, microfluidic-assisted processes allow the production of polymer particles with an improved control over their sizes, size distributions, morphologies, and compositions. In this paper, the most common microfluidic devices are reviewed. Both projection photolithography and emulsification processes are reported for the continuous flow synthesis of polymer particles from a stream of polymerizable liquids. For the latter process, two distinct categories of microfluidic devices have been identified: microchannel-based and capillary-based microsystems. For each category, the existing geometries are described and the different emulsification methods including the co-flowing, cross-flowing, or flow-focusing of the continuous and dispersed phases are commented upon. Finally, for each microsystem the various polymer particles achieved in such devices including, but not restricted to, janus, core,shell, or porous particles and capsules are reported. [source] Metal Nanoparticle/Polymer Hybrid Particles: The Catalytic Activity of Metal Nanoparticles Formed on the Surface of Polymer Particles by UV-IrradiationMACROMOLECULAR SYMPOSIA, Issue 1 2009Toshiyuki Tamai Abstract Summary: Polymer particles decorated with metal nanoparticles were prepared by UV-irradiation of polystyrene particles incorporating polymethylphenylsilane (PS/PMPS) and P[S- co -NIPAM]/PMPS particles (NIPAM: N-isopropyl acrylamide) in the presence of metal salts. The metal nanoparticle/polymer hybrid particles were used as a catalyst for the reduction of 4-nitrophenol with NaBH4. The Pd- and Ag-P(S- co -NIPAM)/PMPS hybrid particles had larger metal nanoparticles and the lower catalytic activity than those of Pd- and Ag-PS/PMPS, respectively. The surface functional group of the polymer particles affected the formation of the metal nanoparticles and their catalytic activity. [source] Nanoencapsulation of a hydrophobic compound by a miniemulsion polymerization processJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2004Yingwu Luo Abstract The nanoencapsulation of hydrophobic compounds by miniemulsion polymerization, a convenient one-step encapsulation technique for nanocapsules, was investigated in terms of the thermodynamics and kinetics. The encapsulation was achieved by polymerization inducing phase separation within minidroplets dispersed in an aqueous phase. Thermodynamic factors (the level and type of surfactant, the level of the hydrophilic comonomer, and the monomer/paraffin ratio), kinetic factors (the level of the crosslinking agent or chain-transfer agent), and nucleation modes were all found to have a great influence on the latex morphology. Specifically, for a styrene/paraffin system, there were optimum levels of sodium dodecyl sulfate (1.0 wt %), the hydrophilic comonomer (1.0 wt % methyl acrylate acid), and the chain-transfer agent (0.2 wt % n -dodecanethiol) for obtaining well-defined nanocapsules of paraffin with a styrene/paraffin ratio of 1:1. When the styrene/paraffin ratio was reduced, however, it was more difficult to achieve a fully encapsulated particle morphology. Homogeneous nucleation could compete with encapsulation, and this resulted in a pure polymer particle and a half-moon morphology. Conditions were also found under which complete encapsulation could be observed with a water-soluble initiator (potassium persulfate), contrary to certain reports. Replacing potassium persulfate with an oil-soluble initiator (2,2-azobisisobutyronitrile) had little influence on the morphology under those conditions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2145,2154, 2004 [source] Synthesis and Characterization of Highly Dispersed Antimony-Doped Stannic Hydroxide Nanoparticles: Effects of the Azeotropic Solvents to Remove Water on the Properties and Microstructures of the NanoparticlesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2007Fen Yang Highly dispersed antimony (Sb)-doped stannic hydroxide nanoparticles have been successfully prepared using the solution chemistry method. The properties and microstructures of the nanoparticles are investigated in detail by means of infrared, transmission electron microscope, X-ray diffractometer, and Brunauer-Emmett-Teller nitrogen surface area measurements. The results indicate that the properties and microstructures of the nanoparticles strongly depend on the azeotropic solvents used to remove water at the drying stage. Various azeotropic solvents are screened to investigate their effects on the size and dispersivity of dried Sb-doped stannic hydroxide. Three empirical rules are drawn for selecting an effective azeotropic solvent: (1) the solvent molecule should contain at least one atom such as oxygen as the hydrogen (H)-bond acceptor to form H bonds with the surface ,OH (acting as an H-bond donor) of polymer particle; (2) the H-bond acceptor should locate in the middle of the alkane chain rather than on the terminal so that the alkane chain can stretch out and cover more surface area, improving the dispersivity of the dried product; and (3) the solvent should have a higher boiling point (,140°C) to reduce the time of azeotropic distillation for removing water and maintain a lower residual amount of azeotropic agent. Based on the empirical rules, it is discovered that iso-amyl acetate is the most effective azeotropic solvent. [source] Separation of cationic polymer particles and characterization of avidin-immobilized particles by capillary electrophoresisELECTROPHORESIS, Issue 5-6 2006Yukihiro Okamoto Abstract Cationic polymer microparticles have received much attention especially in the field of biotechnology, such that their analysis and separation have become important. So far, the separation of cationic polymer particles with different size using CE has not been achieved and the cationic particles migrated as if they are negatively charged, probably due to electrostatic interaction between capillary wall and cationic polymer particles. In this paper, the separation of cationic polymer microparticles by CE was investigated in detail. The separation of cationic particles with different size was achieved in CE by taking into account the interaction between sample particles and the inner surface of capillaries. By employing a poly(vinyl alcohol)-coated capillary, a better size separation of amine-modified latex particles was obtained compared to a Polybrene-coated capillary. It was elucidated that the composition, concentration, and pH of the background solution were also important factors in the separation of colloidal particles to avoid the surface adsorption and the characteristic aggregation of polymer particles. Furthermore, the CE analysis was applied to the characterization of cationic protein-immobilized particles. [source] Ab initio Emulsion Polymerization by RAFT (Reversible Addition,Fragmentation Chain Transfer) through the Addition of CyclodextrinsHELVETICA CHIMICA ACTA, Issue 8 2006Bojana Apostolovic Abstract A novel process to produce homo- and copolymers by RAFT polymerization in emulsion is presented. It is known that RAFT-controlled radical polymerization can be conducted in emulsion polymerization without disturbing the radical segregation characteristic of this process, thus leading to polymerization rates identical to those encountered in the corresponding nonliving systems. However, RAFT agents are often characterized by very low water solubility and, therefore, they diffuse very slowly from the monomer droplets, where they are initially solubilized, to the reaction loci, i.e., the polymer particles. Accordingly, when used in emulsion polymerization, they are practically excluded from the reaction. In this work, we show that cyclodextrins, well-known for their ability to form water-soluble complexes with hydrophobic molecules, facilitate the transport across the H2O phase of the RAFT agent to the polymer particles. Accordingly, chains grow through the entire process in a controlled way. This leads to the production of low-polydispersity polymers with well-defined structure and end functionalities as well as to the possibility of synthesizing block copolymers by a radical mechanism. [source] Biocompatible Polymers: Structurally Controlled Bio-hybrid Materials Based on Unidirectional Association of Anisotropic Microparticles with Human Endothelial Cells (Adv. Mater.ADVANCED MATERIALS, Issue 48 200948/2009) Biocompatible anisotropic polymer particles with bipolar affinity towards human endothelial cells are a novel type of building blocks for microstructured biohybrid materials, report Joerg Lahann and co-workers on p. 4920. Functional polarity due to two biologically distinct hemispheres has been achieved by synthesis of anisotropic particles via electro-hydrodynamic co-jetting of two different polymer solutions and subsequent selective surface modification. [source] Structurally Controlled Bio-hybrid Materials Based on Unidirectional Association of Anisotropic Microparticles with Human Endothelial CellsADVANCED MATERIALS, Issue 48 2009Mutsumi Yoshida Biocompatible anisotropic polymer particles with bipolar affinity towards human endothelial cells are a novel type of building blocks for microstructured bio-hybrid materials. Functional polarity due to two biologically distinct hemispheres (see figure) has been achieved by synthesis of anisotropic particles via electro-hydrodynamic co-jetting of two different polymer solutions and subsequent selective surface modification. [source] Three-Dimensional Fabrication by Reaction-Diffusion: "Remote" Fabrication via Three-Dimensional Reaction-Diffusion: Making Complex Core-and-Shell Particles and Assembling Them into Open-Lattice Crystals (Adv. Mater.ADVANCED MATERIALS, Issue 19 200919/2009) Reaction-diffusion processes initiated from the surfaces of small gel or polymer particles can fabricate complex three-dimensional structures inside these particles. Bartosz Grzybowski and co-workers show on page 1911 that the core/shell particles thus prepared can be further modified "remotely" by electrochemical exchange reactions. The image shows four cubical particles, each having a spherical core fabricated by reaction-diffusion and comprising copper nanoparticles. [source] Morphology-Selective Formation and Morphology-Dependent Gas-Adsorption Properties of Coordination Polymer ParticlesADVANCED MATERIALS, Issue 6 2009Hee Jung Lee Three coordination polymer particles (CPPs) are selectively synthesized using the solvothermal method. All three CPPs are prepared from the same building blocks. However, they form different morphologies, such as elongated hexagons, ellipsoids, and rods. Gas-adsorption measurements on N2, CO2, and H2 reveal that diversely shaped CPPs have different gas-adsorption properties, even though they have the same chemical compositions. [source] Preparation of ultra-high-molecular-weight polyethylene and its morphological study with a heterogeneous Ziegler,Natta catalystJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010G. H. Zohuri Abstract Ultra-high-molecular-weight polyethylene (PE) with viscosity-average molecular weight (Mv) of 3.1 × 106 to 5.2 × 106 was prepared with a heterogeneous Ziegler,Natta MgCl2 (ethoxide type)/TiCl4/triethylaluminum catalyst system under controlled conditions. The optimum activity of the catalyst was obtained at a [Al]/[Ti] molar ratio of 61 : 1 and a polymerization temperature of 60°C, whereas the activity of the catalyst increased with monomer pressure and decreased with hydrogen concentration. The titanium content of the catalyst was 2.4 wt %. The rate/time profile of the catalyst was a decay type with a short acceleration period. Mv of the PE obtained decreased with increasing hydrogen concentration and polymerization temperature. The effect of stirrer speeds from 100 to 400 rpm did not so much affect the catalyst activity; however, dramatic effects were observed on the morphology of the polymer particles obtained. A stirrer speed of 200 rpm produced PE with a uniform globulelike morphological growth on the polymer particles. The particle size distributions of the polymer samples were determined and were between 14 and 67 ,m. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Electrosprayed polymer particles: Effect of the solvent propertiesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2009Chul Ho Park Abstract Electrospraying technology has been studied in many fields to produce particles of various substances from nanoscale to microscale sizes. Unlike pure liquids, droplets formed by electrospraying that are comprised of polymer solutions undergo additional solidification processes involving solvent evaporation, which primarily determine the particle size and morphology. Herein, the effects of the solvent properties on the morphology and dimensions of solidified particles were systematically studied. In general, the size of the solidified spherical particles with smooth surfaces reflected that of the initially formed liquid droplets, which could partially be estimated by theoretical equations developed for pure liquids. Particle sizes increased with an increase in polymer content and a decrease in the boiling point of the volatile solvent. Inhomogeneous drying processes related to phase separation or skin formation resulted in hollow, cuplike, and porous particle structures, with particle sizes and morphologies that were outside of the scope of the theoretical treatments. The selection of a proper solvent or solvent mixture seemed to be a convenient way to control the particle morphologies, such as hollow, cuplike, or porous structures. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Dimethylsilylbis(1-indenyl) zirconium dichloride/methylaluminoxane catalyst supported on nanosized silica for propylene polymerizationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008Kuo-Tseng Li Abstract A dimethylsilylene-bridged metallocene complex, (CH3)2Si(Ind)2ZrCl2, was supported on a nanosized silica particle, whose surface area was mostly external. The resulting catalyst was used to catalyze the polymerization of propylene to polypropylene. Under identical reaction conditions, a nanosized catalyst exhibited much better polymerization activity than a microsized catalyst. At the optimum polymerization temperature of 55°C, the former had 80% higher activity than the latter. In addition, the nanosized catalyst produced a polymer with a greater molecular weight, a narrower molecular weight distribution, and a higher melting point in comparison with the microsized catalyst. The nanosized catalyst's superiority was ascribed to the higher monomer concentration at its external active sites (which were free from internal diffusion resistance) and was also attributed to its much larger surface area. Electron microscopy results showed that the nanosized catalyst produced polymer particles of similar sizes and shapes, indicating that each nanosized catalyst particle had uniform polymerization activity. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Dispersion polymerization of vinyl monomers in supercritical carbon dioxide in the presence of drug molecules: A one-pot route for the preparation of controlled delivery systemsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2008Alessandro Galia Abstract The polymerization of 1-vinyl-2-pyrrolidone in supercritical carbon dioxide in the presence of ibuprofen as a model drug was investigated as a new one-pot process for the preparation of polymer-based drug delivery systems (DDSs). The composites were prepared at 65 °C and P = 31,42 MPa by changing the initial concentration of the drug and the concentration of a crosslinking agent and that of a hydrophobic comonomer. The effects of these parameters on the performances of the polymerization and on the in vitro release kinetics of ibuprofen were studied. In all the experiments, part of the drug was entrapped inside the polymer particles and dissolved more slowly with respect to the pure compound. Copolymerization with methyl methacrylate was the most effective route to obtain a DDS with sustained temporal release of the drug molecule. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7429,7446, 2008 [source] Surfactant assisted polymerization of tetrafluoroethylene in supercritical carbon dioxide with a pilot scale batch reactorJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2008Alberto Giaconia Abstract Chain-free radical polymerization of tetrafluoroethylene (TFE) was carried out in supercritical carbon dioxide (scCO2), at 50 °C and 121,133 bar, with tertiary -amyl-per-pivalate as a free radical initiator, using a 5-L pilot scale batch reactor. Experiments were carried out both in the absence and in the presence of perfluoropolyether (PFPE) carboxylate surfactants. Stabilizers were employed under the free acid form and as sodium and calcium salts. An expanded fibrillated poly(TFE) was obtained in all experiments. In the case of surfactant-free polymerizations, the product was mainly constituted by irregular shape macroparticles having size in the range 200,500 ,m. Quite interestingly, when the free acid surfactant was used, a clear acceleration of the polymerization rate was observed and smaller polymer particles with more regular quasi-spherical morphology were obtained. Melt fusion crystallinity of as-polymerized poly(TFE) seemed not substantially affected by the presence of the stabilizers and was rather high (80,86%) suggesting that polymerization mainly occurs at polymer particle surface. All these elements suggest that FLUOROLINK® 7004H PFPE carboxylic acid decreases coagulation of primary polymer particles leading to an increase in polymer surface area. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 257,266, 2008 [source] Nonaqueous dispersion polymerization of styrene in methanol with the ionomer block copolymer poly[(4-methylstyrene)- co -(4-vinyltriethylbenzyl ammonium bromide)]- b -polyisobutene as a stabilizerJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2004Yuhong Ma Abstract The nonaqueous dispersion polymerization of styrene in methanol with poly[(4-methylstyrene)- co -(4-vinyltriethylbenzyl ammonium bromide)]- b -polyisobutene as a stabilizer was investigated. There was no observable inducing period or autoacceleration in the polymerization process. The conversion increased almost linearly with the polymerization time as high as 80%. The average sizes of the obtained polystyrene particles increased, and the size distributions of the polystyrene particles tended to become narrower, with increasing conversion. The mechanism of the dispersion polymerization in the presence of polyisobutene- b -poly[(4-methylstyrene)- co -(4-vinyltriethylbenzyl ammonium bromide)] was nucleation/growth. When the stabilizer/monomer ratio (w/w) was greater than 2.0%, the polystyrene dispersion was stable, and there was no observable polymer particle coagulation taking place during the whole polymerization process. The average diameter of the polymer particles can be mediated through changes in the polymerization conversion, monomer, and stabilizer. Nearly monodispersed polystyrene particles with average diameters of approximately 0.45,2.21 ,m were obtained under optimal conditions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2678,2685, 2004 [source] Microparticles of poly(methacrylic acid),gadolinium ion complex and their magnetic force microscopic imagesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2004Tsuyoshi Michinobu Abstract Modified poly(methacrylic acid) microparticles complexed with gadolinium(III) (Gd3+) ions were prepared in 100 nm. The emulsion terpolymerization of methacrylic acid, ethyl acrylate, and allyl methacrylate and the following complexation with Gd3+ ions yielded the polymer particles with different Gd3+ ion contents. Potentiometric titration of the complexation of the particle with Gd3+ ions indicated the formation of a very stable tris-carboxylate coordinate complex with the Gd3+ ion. Electron spin resonance and IR spectra of the complexed particles were dependent on the Gd3+ ion content and the coordination environment in each particle. The microparticles dispersed on a mica substrate were subjected to atomic force microscopy (AFM), followed by magnetic force microscopy (MFM). AFM showed 100-nm-sized and monodispersed spherical images. The following MFM clearly provided strong magnetic responses exactly on the same particle positions, of which the images were also dependent on the Gd3+ ion content in the particle. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1912,1918, 2004 [source] Micron-granula polyolefin with self-immobilized nickel and iron diimine catalysts bearing one or two allyl groupsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2004Guoxin Jin Abstract Self-immobilized nickel and iron diimine catalysts bearing one or two allyl groups of [ArNC]2(C10H6)NiBr2 [Ar = 4-allyl-2,6-(i -Pr)2C6H2] (1), [ArNC(Me)][Ar,N C(Me)]C5H3NFeCl2 [Ar = Ar, = 4-allyl-2,6-(i -Pr)2C6H3, Ar = 2,6-(i -Pr)2C6H3, and Ar, = 4-allyl-2,6-(i -Pr)2C6H3] were synthesized and characterized. All three catalysts were investigated for olefin polymerization. As a result, these catalysts not only showed high activities as the catalyst free from the allyl group, such as [ArNC]2C10H6NiBr2 (Ar = 2,6-(i-Pr)2C6H2)], but also greatly improved the morphology of polymer particles to afford micron-granula polyolefin. The self-immobilization of catalysts, the formation mechanism of microspherical polymer, and the influence on the size of the particles are discussed. The molecular structure of self-immobilized nickel catalyst 1 was also characterized by crystallographic analysis. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1018,1024, 2004 [source] Fluorescent polymer particles by emulsion and miniemulsion polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2003Frédéric Tronc Abstract We describe the synthesis and characterization of latex particles labeled with a brightly fluorescent yellow dye (HY) based on the benzothioxanthene ring structure. Three dye derivatives were synthesized with different spacers connecting the HY nucleus to a methacrylate group. For one of the dyes (HY2CMA, rA), we show that the reactivity ratios with styrene (rA = 0.71, rB = 0.25) and butyl methacrylate (rA = 0.87, rB = 0.14) should lead to random dye incorporation if the amount of dye in the feed is small. Seeded emulsion polymerization fails to lead to significant dye incorporation unless large amounts of nonionic surfactant are present. In contrast, miniemulsion polymerization worked well to yield latex particles of polystyrene, poly(butyl methacrylate), and poly(methyl methacrylate) with high monomer conversion and essentially quantitative dye incorporation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 766,778, 2003 [source] Synthesis of highly crosslinked monodisperse polymer particles: Effect of reaction parameters on the size and size distributionJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2002J. Choi Abstract Monodisperse polystyrene particles crosslinked with different concentrations of divinylbenzene were synthesized in the 3.2,9.1 ,m size range by dispersion polymerization in an isopropyl alcohol/toluene mixed-dispersion medium with poly(N -vinylpyrrolidone) as a steric stabilizer and 2,2,-azobisisobutyronitrile as a radical initiator. The effects of the reaction parameters such as the crosslinking agent concentration, media solvency (controlled by varying the amount of toluene addition), the initiator concentration, and the stabilizer concentration on the particle size and size distribution were investigated with reference particles with a monodisperse size distribution and crosslinked by 1.5 wt % divinylbenzene. The appropriate increase in media solvency was a prerequisite for preparing crosslinked particles without coagulated and/or odd-shaped particles. The investigation of the effects of the polymerization parameters also shows that only specific sets of conditions produce particles with a monodisperse size distribution. The glass-transition temperatures of the particles increased with increasing divinylbenzene concentration. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4368,4377, 2002 [source] Particle formation under monomer-starved conditions in the semibatch emulsion polymerization of styrene.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2001Abstract Particle formation and particle growth compete in the course of an emulsion polymerization reaction. Any variation in the rate of particle growth, therefore, will result in an opposite effect on the rate of particle formation. The particle formation in a semibatch emulsion polymerization of styrene under monomer-starved conditions was studied. The semibatch emulsion polymerization reactions were started by the monomer being fed at a low rate to a reaction vessel containing deionized water, an emulsifier, and an initiator. The number of polymer particles increased with a decreasing monomer feed rate. A much larger number of particles (within 1,2 orders of magnitude) than that generally expected from a conventional batch emulsion polymerization was obtained. The results showed a higher dependence of the number of polymer particles on the emulsifier and initiator concentrations compared with that for a batch emulsion polymerization. The size distribution of the particles was characterized by a positive skewness due to the declining rate of the growth of particles during the nucleation stage. A routine for monomer partitioning among the polymer phase, the aqueous phase, and micelles was developed. The results showed that particle formation most likely occurred under monomer-starved conditions. A small average radical number was obtained because of the formation of a large number of polymer particles, so the kinetics of the system could be explained by a zero,one system. The particle size distribution of the latexes broadened with time as a result of stochastic broadening associated with zero,one systems. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3940,3952, 2001 [source] Mechanism of emulsion polymerization of styrene using a reactive surfactantJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2001X. Wang Abstract The emulsion polymerization of styrene using the reactive surfactant sodium dodecyl allyl sulfosuccinate (TREM LF-40) was studied. The polymerization kinetics were found to be unusual in that Rp was not directly proportional to Np (Rp , Np0.67). Several reasons are stated to explain the unusual kinetics, including chain transfer to TREM LF-40, copolymerization of styrene with TREM LF-40, and the influence of the homopolymer of TREM LF-40 [poly(TREM)] and/or the copolymer [poly(TREM- co -styrene)] on the entry and exit rates of free radicals. The possibility of both chain transfer and copolymerization exists primarily at the oil/water interface, whereas both can also occur in the aqueous and monomer phases. Bulk polymerizations of styrene in the presence of TREM LF-40 and poly(TREM) were conducted, and the results show that the reaction rate decreased for the styrene/TREM LF-40 system. Latex characterization by serum replacement and titration measurements provided evidence for the chemical bonding of TREM LF-40 to the polymer particles. The fraction of chemically bound reactive surfactant decreased with increasing surfactant concentration and increased with increasing initiator concentration. Relatively high contact angles of water on films cast from the latexes showed that TREM LF-40 did not migrate significantly to the surface of the film, which was consistent with the latex-surface characterization results. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3093,3105, 2001 [source] Ion imprinted polymer particles for separation of yttrium from selected lanthanidesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2006Ramakrishnan Kala Abstract Lanthanide(III) (Dy, Gd, Tb and Y) ion imprinted polymer (IIP) materials were synthesized via single pot reaction by mixing lanthanide imprint ion with 5,7-dichloroquinoline-8-ol, 4-vinylpyridine, styrene, divinylbenzene and 2,2,-azobisisobutyronitrile in 2-methoxyethanol porogen. The imprint ion was removed by stirring the above materials (after powdering) with 6 mol/L HCl to obtain the respective lanthanide IIP particles. Y-Dy, Y-Gd and Dy-Gd polymer particles were obtained by physically mixing equal amounts of the respective leached individual lanthanide(III) particles. Control polymer (CP) particles were similarly prepared without imprint ion. Application of the above synthesized polymer particles was tested for separation of Y from Dy, Gd and Tb employing batch and column SPE methods using inductively coupled plasma atomic emission spectrometry for the determination. Optimization studies show that Y present in 500 mL can be preconcentrated using Dy-Gd IIP particles and eluted with 20 mL of 1.0 mol/L of HCl, providing an enrichment factor of , 25. Dy-Gd IIP particles offer higher selectivity coefficients for Y over other lanthanides compared to other IIP particles and commercial liquid,liquid extractants. Selectivity studies for Y over other coexisting inorganic species (other than lanthanides) were also conducted and the results obtained show a quantitative separation of Y from other inorganics other than Cu(II) and Fe(III). Furthermore, both batch and column studies indicate the purification of yttrium concentrate from 55.0 ± 0.2 to 65.2 ± 0.2% in a single stage of operation. [source] Novel Light Emitting Diode Using Organic Electroluminescence MicrocapsulesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2003Jae-Seok Heo Abstract Novel light emitting diodes (LEDs) were prepared using electroluminescence (EL) material/polymer microcapsules (ELC). N-vinylcarbazole as a hole-transporting component and methyl methacrylate (MMA) were copolymerized for producing the seed particles using dispersion polymerization. An oxadiazole derivative, synthesized as a electron-transporting component, and tris(8-hydroxyquinolinato) aluminium(III) (Alq3) were incorporated into the polymer particles by using the solute co-diffusion method (SCM). The LEDs for the EL characterization were fabricated in a thin sandwich configuration: Al anode/ELC/ITO cathode. The surface imaging of the LED prepared using ELC was performed by atomic force microscopy (AFM). The EL characteristics of the ELC were investigated by UV, photoelectron and luminescence spectroscopy, and the current-voltage and the light-voltage characteristics for the LED were determined. Encapsulation procedure using solute co-diffusion method (SCM). [source] Video Microscopy for the Investigation of Gas Phase CopolymerizationMACROMOLECULAR MATERIALS & ENGINEERING, Issue 11 2005Daniela Ferrari Abstract Summary: Video microscopy as a tool for investigating olefin gas phase copolymerization is presented for the first time in this paper. The central theme of this work is the study of the comonomer effect shown by an unbridged metallocene catalyst supported on silica. By using video microscopy, it is possible to observe the increase in catalytic activity in terms of particle growth as well as monomer consumption. The observation that a more pronounced induction period in the particle growth profile is shown with increasing propylene concentration led us to investigate the copolymers obtained at different polymerization times using 13C NMR analysis and single particle energy dispersive X-ray (EDX mapping). This allowed us to adapt the "polymer growth and particle expansion model" to the copolymerization. Besides physical causes for the comonomer effect, we wanted to determine whether the catalyst structure plays an important role in the comonomer effect. To this end we investigated two metallocenes bearing the same long bridging unit but differing in the ligand bound to the zirconium center. One metallocene bears a cyclopentadienyl ring, while the other bears an indenyl group. From a close analysis of the 13C NMR, it is clear that both catalysts insert ethylene more easily then propylene, probably due to the long bridging unit that results in a narrower aperture angle of the ligand. In addition to this, the indenyl ligand does not allow the formation of propylene blocks even at high propylene concentration. Snapshot of the polymer particles taken after 165 min of ethylene-1-butene copolymerization with catalyst 1. [source] | ||||||||||||||||