Home About us Contact
|
Home About us Contact | ||
|
|
||
Resulting Materials (resulting + material)
Selected AbstractsCover Picture: Synthesis of Gadolinium-Labeled Shell-Crosslinked Nanoparticles for Magnetic Resonance Imaging Applications (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 8 2005Mater. Abstract Robust, amphiphilic core,shell nanoparticles that are selectively labeled with gadolinium in the hydrophilic and water-swollen shell layer are depicted in the cover picture. These well-defined nanostructured materials exhibit high relaxivity, a large loading capacity, and are based upon a biocompatible platform for ultimate function in magnetic resonance imaging (MRI) applications, as reported by Wooley and co-workers on p.,1248. Shell-crosslinked knedel-like nanoparticles (SCKs; "knedel" is a Polish term for dumplings) were derivatized with gadolinium chelates and studied as robust magnetic-resonance-imaging-active structures with hydrodynamic diameters of 40,±,3,nm. SCKs possessing an amphiphilic core,shell morphology were produced from the aqueous assembly of diblock copolymers of poly-(acrylic acid) (PAA) and poly(methyl acrylate) (PMA), PAA52,b,PMA128, and subsequent covalent crosslinking by amidation upon reaction with 2,2,-(ethylenedioxy)bis(ethylamine) throughout the shell layer. The properties of these materials, including non-toxicity towards mammalian cells, non-immunogenicity within mice, and capability for polyvalent targeting, make them ideal candidates for utilization within biological systems. The synthesis of SCKs derivatized with GdIII and designed for potential use as a unique nanometer-scale contrast agent for MRI applications is described herein. Utilization of an amino-functionalized diethylenetriaminepentaacetic acid,Gd analogue allowed for direct covalent conjugation throughout the hydrophilic shell layer of the SCKs and served to increase the rotational correlation lifetime of the Gd. In addition, the highly hydrated nature of the shell layer in which the Gd was located allowed for rapid water exchange; thus, the resulting material demonstrated large ionic relaxivities (39,s,1,mM,1) in an applied magnetic field of 0.47,T at 40,°C and, as a result of the large loading capacity of the material, also demonstrated high molecular relaxivities (20,000,s,1,mM,1). [source] Use of fluorinated maleimide and telechelic bismaleimide for original hydrophobic and oleophobic polymerized networksJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2008Aurélien Soules Abstract The syntheses of original fluorinated maleimide and telechelic bismaleimide bearing C6F13 and C6F12 groups, respectively, and their use as reactive additives in photopolymerizable formulations of telechelic poly(propylene glycol) bismaleimide (PPGBMI) are presented. Fluorinated maleimide was synthetized in five steps in 63% overall yield from C6F13C2H4I precursor, whereas the fluorinated bismaleimide was prepared in six steps in 14% overall yield from IC6F12I. These latter led to fluorinated azido and diazido intermediates that were reduced into the fluorinated amine and diamines in two steps. The condensation of amine and diamine onto maleic anhydride offered an amic acid and a diamic acid, which were subsequently cyclized into fluorinated maleimide and bismaleimide. Formulations of telechelic PPGBMI containing a low concentration of these fluorinated maleimide and bismaleimide were UV cured and the surface properties of the resulting films were investigated. A deep modification of the surface properties was noted when the monomaleimide was used. In all the cases, a selective enrichment of the fluorinated monomer at the film surface was observed. The dependence of the surface properties on the fluorinated maleimide and bismaleimide concentrations were also studied, and showed an asymptotic behavior of the contact angle with only 1.5 wt % of fluorinated maleimide additive, whatever the conditions. This monomaleimide led to better hydrophobic and oleophobic properties of the resulting material than that containing the telechelic one. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3214,3228, 2008 [source] Preparation of Pie-Shaped and Rugged Aromatic Polyamide ParticlesMACROMOLECULAR REACTION ENGINEERING, Issue 5 2008Yayoi Yoshioka Abstract Aromatic polyamide particles were prepared by reacting diamines and diacid chlorides in a reaction solution containing water. They consisted of submicron-sized pie-shaped or rugged spherical particles with a narrow size distribution. The surface morphology of these particles was found to vary with the volume of water added, the reaction solvent, and the monomer concentration, but the degree of crystallinity of the particles obtained was almost the same. In addition, the molecular weight of the resulting material depended on the volume of water added and the monomer concentration. During the particle formation process, the degree of crystallinity was set at the initial stage, and thereafter the morphology and the molecular weight changed gradually with reaction time. [source] Selective Lanthanides Sequestration Based on a Self-Assembled OrganosilicaCHEMISTRY - A EUROPEAN JOURNAL, Issue 33 2010Eric Besson Dr. Abstract In this paper, we investigate the cation-exchange properties of a self-assembled hybrid material towards trivalent ions, lanthanides (La3+, Eu3+, Gd3+, Yb3+) and Fe3+. The bis-zwitterionic lamellar material was prepared by sol,gel process from only 3-aminopropyltriethoxysilane (APTES), succinic anhydride, and ethylenediamine. In ethanol heated under reflux, the exchange ethylenediammonium versus Ln3+ proved to be complete by complexometry measurements and elemental analyses, one Cl, ion per one LnIII remaining as expected for charge balance. In aqueous solution at 20,°C, the material was found to be selective towards lanthanide in spite of the similarity of their ionic radii. The cation uptake depends on the nature of the salt, the difference between two lanthanides reaching up to 20,% in some cases. Finally, ion-exchange reaction with FeCl3 was chosen as a probe to get more information on the material after incorporation of trivalent ions. Based on Mössbauer spectroscopic investigations on the resulting material in conjunction with the XRD analysis of materials containing trivalent ions, a structural model was proposed to describe the incorporation of trivalent ions by exchange reaction within the original zwitterionic material. [source] Syntactic Iron Foams with Integrated Microglass Bubbles Produced by Means of Metal Powder Injection Moulding,ADVANCED ENGINEERING MATERIALS, Issue 7 2010Jörg Weise Systematic tests for the production of pure iron (99%) foams with integrated microglass bubbles by means of metal powder injection moulding (MIM) have been carried out with variation of the glass bubble contents. Process parameters were optimized and the resulting materials characterized using density measurements, tensile and compression tests, metallographic sections, and scanning electron microscopy. The corrosion behavior of this novel material was characterized using potentiodynamic polarization measurements and immersion tests. [source] Controllable Soluble Protein Concentration Gradients in Hydrogel Networks,ADVANCED FUNCTIONAL MATERIALS, Issue 21 2008Brian J. Peret Abstract Here, controlled formation of sustained, soluble protein concentration gradients within hydrated polymer networks is reported. The approach involves spatially localizing proteins or biodegradable, protein-loaded microspheres within hydrogels to form a protein-releasing "depot." Soluble protein concentration gradients are then formed as the released protein diffuses away from the localized source. Control over key gradient parameters, including maximum concentration, gradient magnitude, slope, and time dynamics, is achieved by controlling the release of protein from the depot and subsequent transport through the hydrogel. Results demonstrate a direct relationship between the amount of protein released from the depot and the source concentration, gradient magnitude, and slope of the concentration gradient. In addition, an inverse relationship exists between the diffusion coefficient of protein within the hydrogel and the slope of the concentration gradient. The time dynamics of the concentration gradient profile can be directly correlated to protein release from the localized source, providing a mechanism for temporarily controlling gradient characteristics. Therefore, each key biologically relevant parameter associated with the protein concentration gradient can be controlled by defining protein release and diffusion. It is anticipated that the resulting materials may be useful in 3D cell culture systems, and in emerging tissue engineering approaches that aim to regenerate complex, functional tissues. [source] Replication and Coating of Silica Templates by Hydrothermal Carbonization,ADVANCED FUNCTIONAL MATERIALS, Issue 6 2007M.-M. Titirici Abstract Hierarchical carbon materials with functional groups residing at the surface are prepared for the first time by using nanostructured silica materials as templates in combination with hydrothermal carbonization at mild temperatures (180,°C). Different carbon morphologies (e.g., macroporous casts, hollow spheres, carbon nanoparticles, and mesoporous microspheres) can be obtained by simply altering the polarity of the silica surface. The surface functionality and hydrophilicity of the resulting materials are assessed by Fourier transform IR spectroscopy, X-ray photoelectron analysis, and water porosimetry. Raman spectroscopy and X-ray diffraction measurements show that the materials are of the carbon-black type, similar to charcoal. [source] A New Supramolecular Route for Using Rod-Coil Block Copolymers in Photovoltaic ApplicationsADVANCED MATERIALS, Issue 6 2010Nicolas Sary A new polymer blend formed by poly(3-hexylthiophene)-poly(4-vinylpyridine) (P3HT- P4VP) block copolymers and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) is reported. The P4VP and PCBM are mixed together by weak supramolecular interactions, and the resulting materials exhibit microphase separated morphologies of electron-donor and electron-acceptor rich domains. The properties of the blend, used in photovoltaic devices as active layers, are also discussed. [source] Injectable acrylic bone cements for vertebroplasty with improved propertiesJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2004Raúl García Carrodeguas Abstract Currently commercially available acrylic bone cements lack adequate radiopacity and viscosity when they are used in percutaneous vertebroplasty (PVP). In this work improved formulations of radiopaque and injectable poly(methyl methacrylate) bone cements were prepared with different amounts (10,50 wt.%) of BaTiO3 or SrTiO3 particles as the radiopaque agent. Two sets of cements were prepared by using untreated or silanated radiopaque particles, respectively. The influence of the content and nature of the radiopaque agent as well as its silanation with 3-(trimethoxysilyl) propyl methacrylate (,-MPS), on the curing parameters, residual monomer content, radiopacity, mechanical properties, and injectability of the resulting materials, was examined. Doughing and setting times, maximum temperature, and compressive strength of all formulations fulfilled the requirements of standard specifications, with values of peak temperature in the range 57,72 °C and those of compressive strength between 114 and 135 MPa. Formulations containing at least 20 wt.% BaTiO3 or SrTiO3 had radiopacities equal to or greater than that corresponding to 2 mm of Al as required for surgical plastics. Injectability of any of the formulations provided 75,80 wt.% of the total mass manually injected through a conventional biopsy needle 4 min after mixing. Silanation of the BaTiO3 or SrTiO3 particles led to formulations with improved mechanical properties and injectability compared to those obtained with the untreated fillers. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 68B: 94,104, 2004 [source] Synthesis of thiophene/phenylene co-oligomers.JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2003We report the synthesis of various thiophene/phenylene co-oligomers with a total number of thiophene and benzene (phenylene) rings of 6 to 8. These compounds include a phenyl-capped sexithiophene, a thienyl-capped quaterphenylene, as well as block and alternating co-oligomers. The synthesis is based on either the Suzuki coupling reaction or the direct dimerization coupling. The latter method produces symmetric molecules with an even total ring number. These reaction schemes enabled us to obtain the target compounds in high quality. Although the resulting materials are difficult to dissolve in organic solvents and therefore difficult to identify by usual 1H nmr spectroscopy, they have successfully been identified through Fourier-transform ir spectroscopy. The specific group frequencies of ring-stretching and out-of-plane deformation modes are characteristic of the substitution pattern of the individual thiophene and benzene rings. [source] A Scalable Route to Highly Functionalized Multi-Walled Carbon Nanotubes on a Large ScaleMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 8 2008Xianhong Chen Abstract A scalable and solvent-free chemical process to obtain highly functionalized and dispersible multi-walled carbon nanotubes is reported. Highly functionalized multi-walled carbon nanotubes have been prepared using in situ generated aryl diazonium salts in the presence of ammonium persulfate and 2,2,-azoisobutyronitrile by solvent-free techniques. In the Raman spectra of the resulting materials, characteristic peaks, the D- and G-bands, are shifted by about 10 cm,1 to lower frequencies. At the same time, the relative intensity ratios between the D- and G-bands increase in comparison to that in the spectrum of the purified product. Fourier-transform infrared spectroscopy reveals the presence of the functional groups on the surface. Transmission electron microscopy images directly confirm the significant build-up of sidewall organic moieties on the treated materials. The weight loss of various functional moieties determined by thermogravimetry,differential scanning calorimetry analysis is about 18,33%. The dispersibility of the functionalized materials in solvents, such as chloroform, tetrahydrofuran, and water, is obviously improved. [source] Synthesis of Polyurethane/Poly(1,1,2,2-tetrahydroperfluorodecyl acrylate) Particles in Supercritical Carbon DioxideMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 5 2008Benjamin Renault Abstract A new range of end-functionalized poly(1,1,2,2-tetrahydroperfluorodecyl acrylate)s was synthesized by ATRP. Such macromonomers were used as reactive and steric stabilizers for the preparation of original core-shell polyurethane particles in supercritical carbon dioxide. The nature of the chain end functionality, as well as the molar mass of the reactive stabilizer, were varied in order to investigate the role of such parameters on the properties of the resulting materials. Due to the low surface energy of PFDA combined with the high surface roughness induced by the specific microstructure of particles deposited on a silica plate, PUR materials exhibited super-hydrophobic behavior with a water CA above 150°. [source] Sequential Polymer Precipitation of Core,Shell Microstructured Composites with Giant PermittivityMACROMOLECULAR RAPID COMMUNICATIONS, Issue 5 2010Tingyang Dai Abstract Polymeric core,shell microstructures have been constructed through a new method, namely sequential precipitation, which is intrinsically a self-assembly and phase separation process. High-quality poly(vinyldene fluoride),polycarbonate,lithium perchlorate composite films with spherical core,shell microstructures have been prepared and determined to consist of conducting cores and insulating shells. Because of the percolation effect, the resulting materials present a dielectric constant as high as 104,107 at the threshold. [source] Effect of different types of peroxides on properties of vulcanized EPDM + PP blendsPOLYMER COMPOSITES, Issue 10 2010Witold Brostow Mechanical and tribological behavior of several dynamic vulcanizate blends of polypropylene (PP) with ethylene-propylene-diene rubber (EPDM) was examined and compared with those of uncrosslinked blends. Vulcanization was performed using two types of organic peroxides combined with (meth)acrylate coagent. The effect of different types and concentrations of peroxides as crosslinking agents on the properties of the resulting materials were investigated. Dicumyl peroxide (DCP) provides higher reactivity and exhibits nearly the same crosslinking efficiency for both 60/40 and 50/50 blends; almost fully crosslinked samples are obtained if the compound contains 1.0 or 2.0 wt% DCP. These results correlate to the gel content and mechanical properties of our materials. Variation of PP + elastomer ratio does not have a significant influence on friction. From 60/40 group of composites, lower friction values were obtained for samples cured with 0.5 wt% benzoyl peroxide (BP) and 1.0 wt% DCP. The tribological properties of the samples with higher amount of DCP show rubbery rather than a toughened thermoplastic behavior. Wear of the composites decreases with the increasing concentration of the curing agent. Compared to BP, the samples cured with DCP display lower wear. POLYM. COMPOS., 31:1678,1691, 2010. © 2010 Society of Plastics Engineers. [source] Morphology and surface properties of some siloxane,organic copolymersPOLYMER INTERNATIONAL, Issue 6 2009Maria Cazacu Abstract BACKGROUND: It is well known that, due to their extremely low polarity, polysiloxanes are incompatible with almost any organic system. This incompatibility leads to phase separation in mixed siloxane,organic systems. RESULTS: Three siloxane,organic copolymers, poly[(5,5,-methylene-bis-salicylaldehyde)-imine-(1,3-bis(propylene)tetramethyldisiloxane)] (Paz1), poly[(2,5-dihydroxy-1,4-benzoquinone)-imine-(1,3-bis(propylene)tetramethyldisiloxane)] (Paz2) and poly[1,3-bis(propylene)tetramethyldisiloxane diamide] (Pam), were prepared by the reaction of 1,3-bis(3-aminopropyl)tetramethyldisiloxane with appropriate organic partners (5,5,-methylene-bis-salicylaldehyde, 2,5-dihydroxy-1,4-benzoquinone and oxalyl chloride, respectively). The morphologies dictated by the incompatibility between siloxane and polar organic moieties were investigated using differential scanning calorimetry and scanning electron microscopy. The surface activity of the copolymers and water vapour sorption capacity were also measured. CONCLUSION: Even though the polar sequences are very short ones, the highly flexible siloxane-containing sequence permits the self-assembly of these into more or less polar domains. Such an organization influences the properties of the resulting materials, an important place being occupied by the surface properties. Copyright © 2009 Society of Chemical Industry [source] Layered silicate/epoxy nanocomposites: synthesis, characterization and propertiesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 5 2004Nehal A. Salahuddin Abstract Novel epoxy-clay nanocomposites have been prepared by epoxy and organoclays. Polyoxypropylene triamine (Jeffamine T-403), primary polyethertriamine (Jeffamine T-5000) and three types of polyoxypropylene diamine (Jeffamine D-230, D-400, D-2000) with different molecular weight were used to treat Na-montmorillonite (MMT) to form organoclays. The preparation involves the ion exchange of Na+ in MMT with the organic ammonium group in Jeffamine compounds. X-ray diffraction (XRD) confirms the intercalation of these organic moieties to form Jeffamine-MMT intercalates. Jeffamine D-230 was used as a swelling agent for the organoclay and curing agent. It was established that the d001 spacing of MMT in epoxy-clay nanocomposites depends on the silicate modification. Although XRD data did not show any apparent order of the clay layers in the T5000-MMT/epoxy nanocomposite, transmission electron microscopy (TEM) revealed the presence of multiplets with an average size of 5,nm and the average spacing between multiplets falls in the range of 100 Å. The multiplets clustered into mineral rich domains with an average size of 140,nm. Scanning electron microscopy (SEM) reveals the absence of mineral aggregate. Nanocomposites exhibit significant increase in thermal stability in comparison to the original epoxy. The effect of the organoclay on the hardness and toughness properties of crosslinked polymer matrix was studied. The hardness of all the resulting materials was enhanced with the inclusion of organoclay. A three-fold increase in the energy required for breaking the test specimen was found for T5000-MMT/epoxy containing 7,wt% of organoclay as compared to that of pure epoxy. Copyright © 2004 John Wiley & Sons, Ltd. [source] Lanthanide (Eu3+, Tb3+) Centered Mesoporous Hybrids with 1,3-Diphenyl-1,3-Propanepione Covalently Linking SBA-15 (SBA-16) and Poly(methylacrylic acid)CHEMISTRY - AN ASIAN JOURNAL, Issue 7 2010Ya-Juan Li Dr. Abstract 1,3-Diphenyl-1,3-propanepione (DBM)-functionalized SBA-15 and SBA-16 mesoporous hybrid materials (DBM-SBA-15 and DBM-SBA-16) are synthesized by co-condensation of modified 1,3-diphenyl-1,3-propanepione (DBM-Si) and tetraethoxysilane (TEOS) in the presence of Pluronic P123 and Pluronic F127 as a template, respectively. The as-synthesized mesoporous hybrid material DBM-SBA-15 and DBM-SBA-16 are used as the first precursor, and the second precursor poly(methylacrylic acid) (PMAA) is synthesized through the addition polymerization reaction of the monomer methacrylic acid. These precursors then coordinate to lanthanide ions simultaneously, and the final mesoporous polymeric hybrid materials Ln(DBM-SBA-15)3PMAA and Ln(DBM-SBA-16)3PMAA (Ln=Eu, Tb) are obtained by a sol-gel process. For comparison, binary lanthanide SBA-15 and SBA-16 mesoporous hybrid materials (denoted as Ln(DBM-SBA-15)3 and Ln(DBM-SBA-16)3) are also synthesized. The luminescence properties of these resulting materials are characterized in detail, and the results reveal that ternary lanthanide mesoporous polymeric hybrid materials present stronger luminescence intensities, longer lifetimes, and higher luminescence quantum efficiencies than the binary lanthanide mesoporous hybrid materials. This indicates that the introduction of the organic polymer chain is a benefit for the luminescence properties of the overall hybrid system. In addition, the SBA-15 mesoporous hybrids show an overall increase in luminescence lifetime and quantum efficiency compared with SBA-16 mesoporous hybrids, indicating that SBA-15 is a better host material for the lanthanide complex than mesoporous silica SBA-16. [source] Tuneable Mesoporous Materials from ,- D -PolysaccharidesCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 5 2008Robin Holey starch! Mesoporous materials with tuneable characteristics have been prepared from biomass-derived ,- D -polysaccharides by a microwave-assisted strategy. Careful selection of the preparation temperature allows control of the crystallinity, particle morphology and textural properties of the resulting materials, leading to surface areas approaching 200,m2,g,1 and mesopore volumes over 0.6,cm3,g,1. [source] | |||||||||||||||||||||||||