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Promising Material (promising + material)
Selected AbstractsAmperometric Glucose Biosensors Based on Glassy Carbon and SWCNT-Modified Glassy Carbon ElectrodesELECTROANALYSIS, Issue 1 2008Irene Carpani Abstract Different carbonaceous materials, such as single-walled carbon nanotubes (SWCNTs) and glassy carbon submitted to an electrochemical activation at +1.80,V (vs. SCE) for 900,s, have been used with the aim of comparing their performances in the development of enzyme electrodes. Commercial SWCNTs have been pretreated with 2.2,M HNO3 for 20,h prior to use. The utility of activated GC as promising material for amperometric oxidase-based biosensors has been confirmed. With glucose oxidase (GOx) as a model enzyme, glucose was efficiently detected up to 1 mM without the use of a mediator. Both electrodes operated in stirred solutions of 0.1,M phosphate buffer (pH,5.5), containing dissolved oxygen, at a potential of ,0.40,V vs. SCE. Although the performances of the two carbonaceous materials were comparable, the biosensors based on activated GC were characterized by a practically unchanged response 40 days after the fabrication, a better signal to noise ratio, and a little worse sensitivity. In addition, the preparation procedure of such biosensors was more simple, rapid and reproducible. [source] The NADH Electrochemical Detection Performed at Carbon Nanofibers Modified Glassy Carbon ElectrodeELECTROANALYSIS, Issue 14 2007Adina Arvinte Abstract In this work, the capability of carbon nanofibers to be used for the design of catalytic electrochemical biosensors is demonstrated. The direct electrochemistry of NADH was studied at a glassy carbon electrode modified using carbon nanofibers. A decrease of the oxidation potential of NADH by more than 300,mV is observed in the case of the assembled carbon nanofiber-glassy carbon electrode comparing with a bare glassy carbon electrode. The carbon nanofiber-modified electrode exhibited a wide linear response range of 3×10,5 to 2.1×10,3,mol L,1 with a correlation coefficient of 0.997 for the detection of NADH, a high specific sensitivity of 3637.65 (,A/M cm2), a low detection of limit (LOD=3,) of 11,,M, and a fast response time (3,s). These results have confirmed the fact that the carbon nanofibers represent a promising material to assemble electrochemical sensors and biosensors. [source] Nanoscale Grain Refinement and H-Sorption Properties of MgH2 Processed by High-Pressure Torsion and Other Mechanical Routes,ADVANCED ENGINEERING MATERIALS, Issue 8 2010Daniel Rodrigo Leiva MgH2 is a promising material for solid-state hydrogen storage due to its high gravimetric and volumetric storage capacity and its relatively low cost. Severe plastic deformation (SPD) processing techniques are being explored as an alternative to high-energy ball-milling (HEBM) in order to obtain more air resistant materials and reduce processing times. In this work, Mg, MgH2, and MgH2,Fe mixtures were severely mechanically processed by different techniques such as high-pressure torsion (HPT), extensive cold forging, and cold rolling. A very significant grain refinement was achieved when using MgH2 instead of Mg as raw material. The mean crystallite sizes observed ranged from 10 to 30,nm, depending on the processing conditions. Enhanced H-sorption properties were observed for the MgH2 -based nanocomposites processed by HPT when compared with MgH2 mixtures. Additionally, cold forging and cold rolling also proved effective in nanostructuring MgH2. These results suggest a high potential for innovative application with the use of low cost mechanical processing routes to produce Mg-based nanomaterials with attractive hydrogen storage properties. [source] Selective Electron Beam Melting of Cellular Titanium: Mechanical PropertiesADVANCED ENGINEERING MATERIALS, Issue 9 2008P. Heinl Cellular titanium seems to be a promising material for medical implant applications due to an elastic modulus comparable with human bone and an interconnected porosity which facilitates bone ingrowth. This paper reports the mechanical properties of non-stochastic cellular Ti-6Al-4V structures fabricated by Selective Electron Beam Melting depending on different unit cell sizes and varying energy input per unit length of the electron beam. [source] Effect of Hypervelocity Impact on Microcellular Ceramic Foams from a Preceramic PolymerADVANCED ENGINEERING MATERIALS, Issue 11 2003P. Colombo A promising material for hypervelocity impact shields in spacecraft and satellites has been found in lightweight microcellular SiOC foams. The foam stops the projectile and the debris from the impacted bumper facesheet within a few millimeters (see Figure for a cross-section of the crater) at speeds up to 5.1 km,s,1. The impacted SiOC ceramic did not react with incoming debris, and no phase transformation or compositional change was observed. [source] Selective Electrochemical Etching of Single-Walled Carbon NanotubesADVANCED FUNCTIONAL MATERIALS, Issue 22 2009Dacheng Wei Abstract Single-walled carbon nanotubes (SWNTs) are a promising material for future nanotechnology. However, their applications are still limited in success because of the co-existence of metallic SWNTs and semiconducting SWNTs produced samples. Here, electrochemical etching, which shows both diameter and electrical selectivity, is demonstrated to remove SWNTs. With the aid of a back-gate electric field, selective removal of metallic SWNTs is realized, resulting in high-performance SWNT field-effect transistors with pure semiconducting SWNT channels. Moreover, electrochemical etching is realized on a selective area. These findings would be valuable for research and the application of SWNTs in electrochemistry and in electronic devices. [source] A Bipolar Host Material Containing Triphenylamine and Diphenylphosphoryl-Substituted Fluorene Units for Highly Efficient Blue ElectrophosphorescenceADVANCED FUNCTIONAL MATERIALS, Issue 17 2009Fang-Ming Hsu Abstract Highly efficient blue electrophosphorescent organic light-emitting diodes incorporating a bipolar host, 2,7-bis(diphenylphosphoryl)-9-[4-(N,N -diphenylamino)phenyl]-9-phenylfluorene (POAPF), doped with a conventional blue triplet emitter, iridium(III) bis[(4,6-difluoro-phenyl)pyridinato- N,C2´]picolinate (FIrpic) are fabricated. The molecular architecture of POAPF features an electron-donating (p-type) triphenylamine group and an electron-accepting (n-type) 2,7-bis(diphenyl-phosphoryl)fluorene segment linked through the sp3 -hybridized C9 position of the fluorene unit. The lack of conjugation between these p- and n-type groups endows POAPF with a triplet energy gap (ET) of 2.75,eV, which is sufficiently high to confine the triplet excitons on the blue-emitting guest. In addition, the built-in bipolar functionality facilitates both electron and hole injection. As a result, a POAPF-based device doped with 7,wt% FIrpic exhibits a very low turn-on voltage (2.5,V) and high electroluminescence efficiencies (20.6% and 36.7,lm W,1). Even at the practical brightnesses of 100 and 1000,cd m,2, the efficiencies remain high (20.2%/33.8,lm W,1 and 18.8%/24.3,lm W,1, respectively), making POAPF a promising material for use in low-power-consumption devices for next-generation flat-panel displays and light sources. [source] Preparation and properties of the single-walled carbon nanotube/cellulose nanocomposites using N -methylmorpholine- N -oxide monohydrateJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Dong-Hun Kim Abstract Single-walled carbon nanotube (SWNT)/cellulose nanocomposite films were prepared using N -methylmorpholine- N -oxide (NMMO) monohydrate as a dispersing agent for the acid-treated SWNTs (A-SWNTs) as well as a cellulose solvent. The A-SWNTs were dispersed in both NMMO monohydrate and the nanocomposite film (as confirmed by scanning electron microscopy) because of the strong hydrogen bonds of the A-SWNTs with NMMO and cellulose. The mechanical properties, thermal properties, and electric conductivity of the nanocomposite films were improved by adding a small amount of the A-SWNTs to the cellulose. For example, by adding 1 wt % of the A-SWNTs to the cellulose, tensile strain at break point, Young's modulus, and toughness increased , 5.4, , 2.2, and , 6 times, respectively, the degradation temperature increased to 9°C as compared with those of the pure cellulose film, and the electric conductivities at , (the wt % of A-SWNTs in the composite) = 1 and 9 were 4.97 × 10,4 and 3.74 × 10,2 S/cm, respectively. Thus, the A-SWNT/cellulose nanocomposites are a promising material and can be used for many applications, such as toughened Lyocell fibers, transparent electrodes, and soforth. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] ANTIOXIDANT ACTIVITIES AND HYPOLIPIDEMIC EFFECTS OF AN AQUEOUS EXTRACT FROM FLOWER BUDS OF CLEISTOCALYX OPERCULATUS (ROXB.) MERR.JOURNAL OF FOOD BIOCHEMISTRY, Issue 6 2009AND PERRY ABSTRACT The antioxidant activities and hypolipidemic effects of aqueous extract from Cleistocalyx operculatus flower buds (COB) (Roxb.) Merr. and Perry, a commonly used material for drink preparation in Vietnam, were investigated in vitro and in diabetic rats. In vitro, the aqueous extract of COB which has highest phenolic and flavonoid contents showed a strong antioxidant effect and highest pancreatic lipase inhibitory activity when compared with green tea and guava leaf extracts. Oral administration of aqueous extract from COB (500 mg/kg body weight/day) on streptozotocin-induced diabetic rats for 8 weeks resulted in significant reduction in the levels of glucose, total cholesterol and triglyceride in plasma as well as the concentration of glucose and sorbitol in the lens. In addition, COB showed significant recovery in the activities of antioxidant enzymes (superoxide dismutase, glutathione S-transferase) and glutathione level in liver with markedly decrease in the lipid peroxide level in liver and lens of the COB-treated diabetic rats. These results indicated that COB showed antioxidant activities, prevention of sorbitol accumulation in lens and hypolipidemic effects in addition to its antidiabetic effects and may be considered as a promising material for the prevention of diabetic complications and metabolic syndrome. PRACTICAL APPLICATIONS In recent years, research on traditional medicinal plants for the management of diabetes has attracted the interest of medical scientists. A suitable plant material for antidiabetes and prevention of diabetic complications should possess various biological components, such as antihyperglycemia, antioxidant activities and antihyperlipidemia, without side effects. In this study, the aqueous extract from Cleistocalyx operculatus flower buds (COB) with high polyphenolic and flavonoid content has shown beneficial biological functions in vitro and in diabetic rats, including antioxidant activity, hypolipidemic and hypoglycemic effects. The results of our study suggest that COB might have a potential role in the management of the prediabetic state and the prevention of diabetic complications. Therefore, there is the possibility for the development of C. operculatus as a beverage for the prevention of diabetes, as well as the prevention of the metabolic syndrome. [source] Molecular simulation of separation of CO2 from flue gases in CU-BTC metal-organic frameworkAICHE JOURNAL, Issue 11 2007Qingyuan Yang Abstract In this work, a computational study was performed on the adsorption separation of CO2 from flue gases (mixtures of CO2/N2/O2) in Cu-BTC metal-organic framework (MOF) to investigate the applicability of MOFs to this important industrial system. The computational results showed that Cu-BTC is a promising material for separation of CO2 from flue gases, and the macroscopic separation behaviors of the MOF were elucidated at a molecular level to give insight into the underlying mechanisms. The present work not only provided useful information for understanding the separation characteristics of MOFs, but also showed their potential applications in chemical industry. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source] The temperature dependence of the band edge energy in calcium barium niobatePHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 7 2010Urs Heine Abstract The temperature dependent band edge energy of the novel tungsten bronze type calcium barium niobate (CBN) is measured over a temperature range from 80 K to 573 K. CBN has been under investigation for serveral years and is believed to be a promising material for future applications. Czochralski-grown, colorless single crystals from the congruently melting composition with a calcium content of 0.281 were used. A numerical fit has been applied, comparing the results of CBN to those of the well known relaxor ferroelectric strontium barium niobate (SBN). The band edge energy of CBN was found to be higher than in SBN over the whole temperature range. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Review Article: ZnO: From basics towards applicationsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 9 2007C. Klingshirn The cover picture of the current issue depicts a selection of luminescence colours of zinc oxide and relates to the Review Article by Claus Klingshirn (University of Karlsruhe) [1]. Zinc oxide is a wide band gap semiconductor which shows intrinsic luminescence in the blue and near-UV spectral range as well as extrinsic emission from the blue to the infrared. The author discusses in detail why ZnO is a promising material for optoelectronics, in particular for the blue and ultraviolet region of the spectrum. His fields of research include the (non)linear, temporally or spatially resolved spectroscopy of semiconductors and their growth by molecular beam epitaxy. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fully unstrained GaN on sacrificial AlN layers by nano-heteroepitaxyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2007K. Tonisch Abstract Usually, the fabrication of microelectromechanical systems (MEMS) requires unstrained or tensile strained active layers on a selectively removable sacrificial layer, since compressive strain causes instabilities due to buckling effects. For group III-nitride based MEMS, AlN is a promising material for sacrificial layers since it can be epitaxially overgrown and etched selectively to GaN. However, due to the larger lattice constants GaN is growing compressively strained on AlN. Nanoheteroepitaxy opens a way to yield fully unstrained, high quality epitaxial GaN layers on nanocrystalline AlN thin film by means of a 3D strain relaxation mechanism. For this purpose sputtered nanocrystalline AlN films were overgrown with single crystalline GaN and AlGaN/GaN layers by metalorganic chemical vapor deposition. The high quality of the layers is proven by an atomically flat surface and a 2D electron gas at the interface of the AlGaN/GaN heterostructure (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Photo- and electroluminescent properties of a ,-conjugated copolymer containing 2,2,-bipyridyl unitsPOLYMER INTERNATIONAL, Issue 2 2007Vitor Angelo Fonseca Deichmann Abstract The synthesis, structural characteristics, and photo- and electroluminescent properties of a soluble light-emitting copolymer built up of regularly alternating segments of 1,4-dihexyloxybenzene and 2,2,-bipyridyl (PBPyDHB) are described and discussed. Optical properties of the polymer were investigated in solution and solid-state conditions, demonstrating that in film form the predominant emission centers are inter-macromolecular aggregates, either in photo- or electroluminescence. Thermogravimetric analysis indicates that PBPyDHB has very high thermal stability, with a maximum decomposition rate around 400 °C and onset with 10% mass loss at 342 °C. The polymer is a blue emitter, and the good solubility, thermal behavior, and electroluminescence properties make it a promising material for electro-optical applications. Copyright © 2006 Society of Chemical Industry [source] Elimination of light-induced degradation with gallium-doped multicrystalline silicon wafersPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 4 2003M. Dhamrin Abstract Lifetime stability of gallium-doped multicrystalline silicon wafers has been evaluated under illumination. Quality and stability of the Ga-doped multicrystalline silicon wafers were intensively studied by means of quasi-steady-state photocondcutance lifetime measurement. Results show that as-grown Ga-doped multicrystalline silicon wafers have high lifetimes, and no significant degradation was observed under illumination. The Ga-doped multicrystalline silicon wafers are a promising material for future photovoltaics. Copyright © 2003 John Wiley & Sons, Ltd. [source] The use of porous calcium phosphate scaffolds with transforming growth factor beta 1 as an onlay bone graft substituteCLINICAL ORAL IMPLANTS RESEARCH, Issue 6 2004An experimental study in rats Abstract Objectives: Autogeneous bone grafting is regarded to be the golden standard for onlay grafts, but it requires a harvesting procedure and the remodeling pattern over time is unpredictable. New materials are constantly being sought to overcome these problems. An in vivo experiment was carried out to evaluate whether (1) porous calcium phosphate cement is a suitable biomaterial for onlay bone grafting, and (2) the addition of transforming growth factor beta 1 (TGF-,1) accelerates de novo bone formation inside the cement porosity. Material and methods: A carrier of porous calcium phosphate cement (Calcibon®) was designed and 16 rats received one preshaped implant each. In 8 out of 16 implants 0.75 ,g TGF-,1 was applied. The animals were killed after 4 weeks and the characteristics of tissue ingrowth into the onlay graft were evaluated. Results: Histologic and quantitative histomorphometrical measurements demonstrated osteoid-like tissue formation in both experimental groups. The addition of TGF-,1 did not induce significantly more osteoid-like tissue formation. On the other hand, in TGF-,-loaded implants, a higher number of pores contained an inflammatory infiltrate. Conclusion: This study indicated that porous calcium phosphate cement is a promising material for clinical situations where bone formation has to be supported. Résumé La greffe osseuse autogčne est considérée comme la meilleure technique actuelle pour les greffons onlay mais elle requiert un processus de prélevement et le remodelage qui s'en suit est imprévisible. De nouveaux matériaux sont donc constamment recherchés. Cette étude in vitro a essayé d'évaluer si 1) le cément phosphate calcium poreux était un biomatériel favorable pour le greffage osseux onlay, 2) si l'addition de TGF-,1 accélérait la néoformation osseuse ŕ l'intérieur de la porosité du cément. Un porteur de cément phosphate calcium poreux (Calcibon®) a été fabriqué et seize rats ont reçu chacun un implant prédécoupé. Au niveau de huit des seize implants 0,75 ,g de TGF ,1 a été appliqué. Les animaux ont été euthanasiés aprčs quatre semaines et les caractéristiques de la croissance interne tissulaire dans le greffon onlay ont étéévaluées. Les mesures histologiques et histomorphométriques quantitatives ont démontré une formation tissulaire semblable ŕ l'ostéogénie dans les deux groupes expérimentaux. L'addition de TGF-ß1 n'induisait pas plus de formation tissulaire ressemblant ŕ celle d'ostéogénie. D'un autre côté, dans les implants chargés de TGF-,1, un nombre plus important de pores contenaient un infiltrat inflammatoire. Cette étude indique que le cément phosphate calcium poreux est un matériau prometteur pour les situations cliniques dans lesquelles la formation osseuse doit ętre améliorée. Zusammenfassung Ziel: Die Transplantation von autologem Knochen wird heute als Goldstandard für die Onlay-Transplantate betrachtet. Es braucht dazu aber einen zusätzlichen Eingriff für die Entnahme und eine Prognose bezüglich der anschliessenden Remodellationsvorgänge sind kaum möglich. Man sucht ständig nach neuen Produkten, um diese Probleme zu überwinden. Man führte eine in vivo Studie durch und untersucht, ob (1) ein poröser Kalziumphosphatzement ein brauchbares Biomaterial für ein Onlay-Transplantat ist, und (2) der Zusatz von TGF-,1 die Neubildung von Knochen in den Porositäten des Zementes positiv beeinflusst. Material und Methode: Man entwickelte einen Trägerzement aus porösem Kalziumphosphat (Calcibon®) und 16 Ratten erhielten je ein vorgeformtes Implantat eingesetzt. Bei 8 der 16 Implantate fügte man zusätzlich 0.75 ,g TGF-,1 dazu. Vier Wochen später opferte man die Tiere und konnte nun die Charakteristika des in die Implantate einwachsenden Gewebes untersuchen. Resultate: Die histologischen und quantitativen histomorphometrischen Messungen zeigten in beiden experimentellen Gruppen osteoidähnliche Gewebsbildungen. Der Zusatz von TGF-,1 bewirkte keine signifikante Zunahme dieser osteoidähnlichen Gewebsbildungen. Die mit TGF-,1 durchsetzten Implantate enthielten aber mehr mit entzündlichem Infiltrat angefüllte Poren. Zusammenfassung: Diese Arbeit zeigte uns, dass ein poröser Kalziumphosphatzement bei klinischen Situationen, wo die Knochenbildung unterstützt werden muss, ein erfolgsversprechendes Material ist. Resumen Objetivos: El injerto de hueso autógeno está considerado como el estándar de oro para injertos superpuestos, pero requiere un procedimiento de recolección y el patrón de remodelado a lo largo del tiempo es impredecible. Constantemente se están buscando materiales nuevos para superar estos problemas. Se llevó a cabo un experimento in vivo para evaluar si (1) el cemento de fosfato cálcico poroso es un biomaterial apropiado para injerto óseo superpuesto, y (2) la adición de TGF-,1 acelera la formación de hueso de novo dentro de la porosidad del cemento. Material y Métodos: Se diseńó un portador de cemento de fosfato cálcico (Calcibon®) y 16 ratas recibieron un implante preformado cada una. En 8 de 16 implantes se aplicaron 0.75 ,g de TGF-,1. Los animales se sacrificaron tras 4 semanas y se evaluaron las características del tejido crecido hacia adentro del injerto superpuesto. Resultados: Las mediciones histológicas e histomorfométricas cuantitativas demostraron formación de tejido tipo osteoide en ambos grupos experimentales. La adición de TGF-,1 no indujo significativamente más formación de tejido tipo osteoide. Por otro lado, en los implantes cargados con TGF-,1, un mayor número de de poros contenían infiltrado inflamatorio. Conclusión: Este estudio indica que el cemento de fosfato cálcico poroso es un material prometedor para situaciones clínicas donde la formación de hueso ha de ser favorecida. [source] New Insights on Near-Infrared Emitters Based on Er-quinolinolate Complexes: Synthesis, Characterization, Structural, and Photophysical Properties,ADVANCED FUNCTIONAL MATERIALS, Issue 14 2007F. Artizzu Abstract Erbium quinolinolates, commonly assumed to be mononuclear species with octahedral co-ordination geometry, have been proposed as promising materials for photonic devices but difficulties in obtaining well defined products have so far limited their use. We report here the conditions to obtain in high yields three different kinds of pure neutral erbium quinolinolates by mixing an erbium salt with 8-quinolinol (HQ) and 5,7-dihalo-8-quinolinol (H5,7XQ: X,=,Cl and Br): i),the trinuclear complex Er3Q9 (1) which is obtained with HQ deprotonated by NH3 in water or ethanol/water mixtures; ii),the already known dimeric complexes based on the unit [Er(5,7XQ)3(H2O)2] [X,=,Cl (2) and Br (3)]; iii) the mononuclear [Er(5,7XQ)2(H5,7XQ)2Cl] [X,=,Cl (4) and Br (5)] complexes, obtained in organic solvents without base addition, where the ion results coordinated to four ligands, two deprotonated chelating, and two as zwitterionic monodentate oxygen donors. These results represent a further progress with respect to a recent reinvestigation on this reaction, which has shown that obtaining pure and anhydrous octahedral ErQ3, the expected reaction product, is virtually impossible, but failed in the isolation of 1 and of the neutral tetrakis species based on H5,7XQ ligands. Structural data provide a detailed description of the molecules and of their packing which involves short contacts between quinoxaline ligands, due to ,,, interactions. Electronic and vibrational studies allow to select the fingerprints to distinguish the different products and to identify the presence of water. The structure/property relationship furnishes a satisfactory interpretation of the photo-physical properties. Experimental evidence confirms that the most important quenchers for the erbium emission are the coordinated water molecules and shows that the ligand emission is significantly affected by the ,,, interactions. [source] Rietveld structure and in vitro analysis on the influence of magnesium in biphasic (hydroxyapatite and ,-tricalcium phosphate) mixturesJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2009S. Kannan Abstract The structure of two different Mg-substituted biphasic (HAP and ,-TCP) mixtures along with the biphasic mixtures without substituted Mg2+ was investigated using Rietveld refinement technique. The substituted Mg2+ was found in the ,-TCP phase and its influence on the composition has led to an increase in HAP content of Mg-containing biphasic mixtures when compared with the HAP content detected in pure biphasic mixtures. The refined structural parameters of Ca10(PO4)6(OH)2 and ,-Ca3(PO4)2 confirmed that all the investigated compositions have crystallized in the corresponding hexagonal (space group P63/m) and rhombohedral (space group R3c) structures. The substitution of lower sized magnesium was found preferentially incorporated at the sixfold-coordinated Ca (5) site of ,-TCP, which is due to the strong Ca (5)·O interaction among all the five different Ca sites of ,-Ca3(PO4)2. The in vitro tests using primary culture of osteoblasts showed that all the tested samples are biocompatible and promising materials for in vivo studies. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source] A versatile approach for the syntheses of poly(ester amide)s with pendant functional groupsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2009Katelyn M. Atkins Abstract Poly(ester amide)s (PEAs) are emerging as promising materials for a wide range of biomedical applications due to their potential for both hydrolytic and enzymatic degradation, as well as the ease with which their properties can be tuned by the choice of monomers. The incorporation of pendant functional handles along the PEA backbone has the potential to further expand their applications by allowing the charge and hydrophilicity of the polymers to be altered, and facilitating the conjugation of active molecules such as drugs, targeting groups, and cell signaling molecules. Described here is a simple and versatile strategy based on orthogonal protecting groups, by which L -lysine and L- aspartic acid can be incorporated into several families of PEAs based on monomers including the diacids succinic and terephthalic acid, the diols 1,4-butanediol and 1,8-octanediol, and the amino acids L- alanine and L- phenylalanine. All polymers were thoroughly characterized by nuclear magnetic resonance spectroscopy, infrared spectroscopy, size exclusion chromatography, thermogravimetric analysis, and differential scanning calorimetry. It was demonstrated that the side chain protecting groups could be readily removed, allowing the pendant amines or carboxylic acids to be functionalized. In particular, the carboxylic acid groups on a polymer containing L- aspartic acid units were converted to N -hydroxysuccinimidyl esters, providing a useful template for further derivatization. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3757,3772, 2009 [source] Hybrid linear dendritic macromolecules: From synthesis to applicationsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2008Ivan Gitsov Abstract Linear-dendritic copolymers are intriguing macromolecules, which offer challenge and fascination as purely synthetic objects at the crossroad of organic and polymer chemistry and as promising materials for diverse advanced applications. This review traces their discovery and highlights the synthetic strategies used for their construction. The ambivalent character of the linear-dendritic architecture opens numerous avenues towards emerging and potential applications. Specific solution properties enable the construction of nanometer-sized nanoreactors for reactions in environmentally friendly media, and the creation of "nanosponges" for selective passive binding of fluorescent pH-indicators for environmental or biomonitoring. Another structure,property relationship is used for noncovalent and site-specific modification of glycoproteins, which leads to the formation of "semiartificial" enzymes with enhanced and broadened catalytic activity. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5295,5314, 2008 [source] Indication of Local Phase Separation in Polyimide/Silica Hybrid Polymers,MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2010Antonino Bartolotta Abstract PI/SiO2 hybrid polymers involving the in situ generation of SiO2 particles through the sol/gel route have emerged as promising materials in many fields of modern technology thanks to their unique structural characteristics. In this paper their structural and dynamic properties were investigated by FT-IR and DMTA as a function of SiO2 content. All data consistently highlight a loosening of polymeric structure due to the presence of SiO2 nanoparticles and suggest a silica-induced structural change most probably due to a sub-micrometer scale SiO2 phase separation. Our results demonstrate how the analysis of sub-glass ,-relaxation dynamics can be exploited to investigate sub-micro phase segregation in such materials. [source] Ferrimagnetism and antiferro- magnetism in half-metallic Heusler alloysPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2008Iosif Galanakis Abstract Half-metallic Heusler alloys are among the most promising materials for future applications in spintronic devices. Although most Heusler alloys are ferromagnets, ferrimagnetic or antiferromagnetic (also called fully-compensated ferrimagnetic) alloys would be more desirable for applications due to the lower stray fields. Ferrimagnetism can be either found in perfect Heusler compounds or achieved through the creation of defects in ferromagnetic Heusler alloys. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Sulfonated poly(phenylene oxide) membranes as promising materials for new proton exchange membranesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 5 2006Shifang Yang Abstract Poly(phenylene oxide) (PPO) was sulfonated to different ion exchange capacities (IECs) using chlorosulfonic acid as the sulfonating agent. Tough, ductile films were successfully cast from sulfonated PPO (SPPO) solutions in N -methyl-2-pyrrolidone or N,N -dimethylformamide. The obtained membranes had good thermal stability revealed by thermogravimetric analysis (TGA). Compared with an unsulfonated PPO membrane, the hydrophilicity and water uptake of the SPPO membranes were enhanced, as shown by reduced contact angles with water. The tensile test indicated that the SPPO membranes with IEC ranging from 0.77 to 2.63,meq/g were tough and strong at ambient conditions and still maintained adequate mechanical strength after immersion in water at room temperature for 24,hr. The results of wide-angle X-ray diffraction (WAXD) showed amorphous structures for PPO and SPPO while the peak intensity decreased after sulfonation. The proton conductivity of these SPPO membranes was measured as 1.16,×,10,2,S/cm at ambient temperature, which is comparable to that of Nafion 112 at similar conditions and in the range needed for high-performance fuel cell proton exchange membranes. Copyright © 2006 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||||||||