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A New Synthetic Approach to Novel Polymers Exhibiting Large Electrooptic Coefficients and High Thermal Stability

Haythem A. Saadeh、Liming Wang、Luping Yu2000-02-17Macromolecules

The Stille coupling reaction was explored to synthesize novel polymers with a pending NLO chromophore exhibiting a large μβ value but high chemical sensitivity. This approach enabled the synthesis of aromatic polyimides through the careful design of dibromo monomers bearing NLO chromophores. The resulting polyimide wa…

Nonlinear Optical Materials ResearchAcoustic Wave Resonator TechnologiesSynthesis and properties of polymers

Reentrant melting of two-dimensional colloidal systems

Clemens Bechinger、Qi‐Huo Wei、P. Leǐderer2000-02-17Journal of Physics Condensed Matter

When a two-dimensional colloidal suspension of highly charged particles is subjected to a periodic one-dimensional (1D) light field, a liquid-solid transition can be induced. This phase transition is well known as light-induced freezing. However, upon further increase of the intensity, the crystal is found to remelt (…

Material Dynamics and PropertiesSpectroscopy and Quantum Chemical StudiesElectrostatics and Colloid Interactions

Influence of the Synthesis Additive on the Textural and Structural Characteristics of Sol−Gel Al2O3−TiO2

José Escobar、J.A. de los Reyes、Tomás Viveros2000-02-17Industrial & Engineering Chemistry Research

Al 2 O 3 −TiO 2 materials were prepared by the sol−gel method using different additives (HNO 3, NH 4 OH, and CH 3 COOH) and their physical properties were evaluated by various techniques. The materials at two compositions (Al/Ti atomic ratios = 2 and 25) were synthesized at 278 K and calcined at temperatures from 573…

Catalytic Processes in Materials ScienceMesoporous Materials and CatalysisCatalysis and Oxidation Reactions

Protein interactions near crystallization: a microscopic approach to the Hofmeister series

Roberto Piazza、Matteo Pierno2000-02-17Journal of Physics Condensed Matter

The salting-out effect of simple electrolytes on lysozyme has been studied by measuring the second virial coefficient B 2 of the osmotic pressure as a function of salt concentration, and for different salts. The aim of this work has been to find a microscopic counterpart of the empirical Hofmeister series for the effi…

Phase Equilibria and ThermodynamicsThermodynamic properties of mixturesCrystallization and Solubility Studies

Synthesis, Crystal Structure, Magnetic, and Electron Paramagnetic Resonance Properties of a Spiroconjugated Biradical. Evidence for Spiroconjugation Exchange Pathway

Natia L. Frank、Farzaneh Fadaei‐Tirani、Jean‐Pascal Sutter 等 9 位作者2000-02-17Journal of the American Chemical Society

A spiroconjugated nitronyl nitroxide biradical, 6,6‘-(4,4,5,5-tetramethylimidazolidine-3-oxide-1-oxyl)-3,3,3‘,3‘-tetramethyl-1,1‘-spirobisindane ( 1 ), has been prepared by functionalization of a 3,3,3‘,3‘-tetramethyl-1,1‘-spirobisindane framework followed by Ullman condensation and subsequent oxidation. The biradical…

Magnetism in coordination complexesOrganic and Molecular Conductors ResearchElectron Spin Resonance Studies

Polymerization of Lactides and Lactones. 10. Synthesis, Characterization, and Application of Amino-Terminated Poly(ethylene glycol)-co-poly(ε-caprolactone) Block Copolymer

Minglong Yuan、Yahui Wang、Xiaohong Li 等 5 位作者2000-02-17Macromolecules

The synthesis of hydroxy-terminated poly(ethylene glycol)- co -poly(ε-caprolactone) (MPEG−PCL) was investigated by the reaction of poly(ethylene glycol) and ε-caprolactone in the presence of stannous octoate. The polymerization was proved to be carried out in a controllable way. Bromo-terminated MPEG−PCL copolymer has…

Advanced Polymer Synthesis and Characterizationbiodegradable polymer synthesis and propertiesBiopolymer Synthesis and Applications

Water in confined geometries: experiments and simulations

Maria Antonietta Ricci、Fabio Bruni、Paola Gallo 等 5 位作者2000-02-17Journal of Physics Condensed Matter

This paper presents the state-of-the-art in studies of structure and dynamics of water confined in a prototype hydrophilic substrate: porous Vycor glass. Experimental data and molecular dynamics simulations are compared.

Phase Equilibria and ThermodynamicsMaterial Dynamics and PropertiesTheoretical and Computational Physics

Dehydration of the molybdenum trioxide hydrates MoO3·nH2O:in situx-ray absorption spectroscopy study at the Mo K edge

Alexei Kuzmin、J. Purāns2000-02-17Journal of Physics Condensed Matter

The process of dehydration for the molybdenum trioxide hydrates, MoO 3 2H 2 O 2-MoO 3 H 2 O -MoO 3 , was studied for the first time by in situ Mo K-edge x-ray absorption spectroscopy. A regularization procedure was applied to reconstruct the radial distribution functions around the molybdenum at all stages of the proc…

Transition Metal Oxide NanomaterialsX-ray Spectroscopy and Fluorescence AnalysisCatalysis and Oxidation Reactions

Evidence of Nonlinear Chain Stretching in the Rheology of Transient Networks

Y. Séréro、V. Jacobsen、Jean‐François Berret 等 4 位作者2000-02-17Macromolecules

We report on telechelic associating polymers in aqueous solutions that self-assemble into starlike flowers in the dilute regime and develop a fully connected network of flowers above some threshold concentration φ* (∼1 wt %). The peculiarity of these telechelics is that the end caps are partially fluorinated. Small-an…

Polymer Nanocomposites and PropertiesSurfactants and Colloidal SystemsPolymer composites and self-healing

Crystal Structures of Fully La3+-Exchanged Zeolite X: an Intrazeolitic La2O3 Continuum, Hexagonal Planar and Trigonally Monocapped Trigonal Prismatic Coordination

Hyun Sook Park、Karl Seff2000-02-17The Journal of Physical Chemistry B

Three single crystals of sodium zeolite X were fully La 3+ -exchanged at 90 °C from aqueous solution (pH = 7.45, 7.45, and 6.89 at 22 °C, respectively). One was vacuum dehydrated at 400 °C (crystal 1), another at 22 °C (crystal 2), and the third remained fully hydrated (crystal 3). Their structures at 22 °C were deter…

Crystal Structures and PropertiesNuclear materials and radiation effectsChemical Synthesis and Characterization

Simultaneously imaging of dielectric properties and topography in a PbTiO_3 crystal by near-field scanning microwave microscopy

Y. G. Wang、M. E. Reeves、F. J. Rachford2000-02-17arXiv

We use a near-field scanning microwave microscope to simultaneously image the dielectric constant, loss tangent, and topography in a PbTiO_3 crystal. By this method, we study the effects of the local dielectric constant and loss tangent in the geometry of periodic domains on the measured resonant frequency, and qualit…

Materials Science

Silence of magnetic layers to magnetoresistive process and electronic separation at low temperatures in (La, Sm)Mn$_2$Ge$_2$

E. V. Sampathkumaran、R. Mallik、P. L. Paulose 等 4 位作者2000-02-17arXiv

A closer look at the temperature (T) dependence of magnetoresistance (MR) of two polycrystalline magnetic compounds, LaMn$_2$Ge$_2$ and SmMn$_2$Ge$_2$, previously reported by us, is made. A common feature for both these compounds is that the low temperature MR is positive (say, below, 30 K) in spite of the fact that b…

Materials ScienceStrongly Correlated Electrons

SODIUM AND ZINC IONOMERS OF SULFONATED MALEATED EPDM RUBBER

Swapan K. Ghosh、P. P. De、Dipak Khastgir 等 4 位作者2000-02-16Polymer-Plastics Technology and Engineering

Sulfonation of maleated EPDM (m-EPDM) rubber followed by its neutralization by sodium hydroxide or zinc acetate leads to the formation of an ionomer consisting of two types of ionic association, namely carboxylate and sulfonate anions with Na+ or Zn2+ as the counterion. The products were characterized by infrared spec…

Polymer Nanocomposites and PropertiesHigh voltage insulation and dielectric phenomenaDielectric materials and actuators

TENSILE PROPERTY OF EPOXIDIZED NATURAL RUBBER/NATURAL RUBBER BLENDS

B. T. Poh、G. K. KHOK2000-02-16Polymer-Plastics Technology and Engineering

The tensile strength and elongation at break of epoxidized natural rubber (ENR) blended with natural rubber (NR) was studied. ENR 25, ENR 50, and one grade of natural rubber (SMR L) were used as the elastomers. The composition of ENR was varied from 0% to 100% rubber. The accelerated sulfur vulcanization system was us…

Polymer crystallization and propertiesPolymer Nanocomposites and Propertiesbiodegradable polymer synthesis and properties

Solid State NMR Study of Water Binding on the Surface of CdS Nanoparticles

Vladimir Ladizhansky、Gary Hodes、Shimon Vega2000-02-16The Journal of Physical Chemistry B

CdS nanoparticles precipitated from aqueous solution were studied by 1 H NMR. The nanoparticles were deliberately not capped by any surface termination agent. The samples had porous structure. Proton high spinning speed magic angle spinning (MAS) NMR spectra revealed that there are three abundant proton species in nan…

Quantum Dots Synthesis And PropertiesChalcogenide Semiconductor Thin FilmsAdvanced NMR Techniques and Applications

Synthesis and Characterization of Various Benzyl Diethylenetriaminepentaacetic Acids (dtpa) and Their Paramagnetic Complexes, Potential Contrast Agents for Magnetic Resonance Imaging

Sophie Laurent、Luce Vander Elst、Sylvain Houzé 等 5 位作者2000-02-16Helvetica Chimica Acta

Four derivatives of diethylenetriaminepentaacetic acid (=3,6,9-tris(carboxymethyl)-3,6,9-triazaundecanedioic acid (H5dtpa)), potential contrast agents for magnetic resonance imaging (MRI), carrying benzyl groups at various positions of the parent structure were synthesized and characterized by a thorough multinuclear…

Magnetism in coordination complexesLanthanide and Transition Metal ComplexesMRI in cancer diagnosis

Modeling Gold Nanoparticles: Morphology, Electron Structure, and Catalytic Activity in CO Oxidation†

L. Guczi、Dániel Vajk Horváth、Zoltán Pászti 等 7 位作者2000-02-16The Journal of Physical Chemistry B

Morphology, electron structure, and catalytic activity in CO oxidation over a Au/FeO x /SiO 2 /Si(100) model sample prepared by pulsed laser deposition (PLD) have been investigated by X-ray photoelectron spectroscopy (XPS), UV photoelectron spectroscopy (UPS), and transmission electron microscopy (TEM). Two types of s…

Catalytic Processes in Materials ScienceCatalysis and Oxidation Reactionsnanoparticles nucleation surface interactions

A STUDY ON MECHANICAL PERFORMANCE OF JUTE-EPOXY COMPOSITES

H K Mishra、B. N. Dash、S. S. Tripathy 等 4 位作者2000-02-16Polymer-Plastics Technology and Engineering

Jute fibers in the form of slivers have been reinforced with epoxy resins to prepare composites. The solution impregnation method has been adopted in an attempt to increase the percentage of fiber loading. Both untreated (control) and chemically modified (bleached) slivers have been used to prepare composites. The opt…

Mechanical Behavior of CompositesNatural Fiber Reinforced CompositesTextile materials and evaluations

ENVIRONMENTALLY FRIENDLY PROCESSING OF POLYURETHANE FOAM FOR THERMAL INSULATION

Chan-Joong Kim、Jae Ryoun Youn2000-02-16Polymer-Plastics Technology and Engineering

An environmentally friendly processing method of polyurethane foam was proposed and evaluated for the application of thermal insulation. For the production of polyurethane foam, chlorofluorocarbon (CFC) gases were eliminated to minimize environmental destruction. Carbon dioxide gas was used as a blowing agent instead…

Electrospun Nanofibers in Biomedical ApplicationsPolymer composites and self-healingPolymer Foaming and Composites

Divalent and Mixed-Valence Samarium Clusters Supported by Dipyrrolide Ligand

Tiffany Dubé、Sabrina Conoci、Sandro Gambarotta 等 4 位作者2000-02-16Organometallics

The nature of the substituents present on a dipyrrolide dianion ligand determines the assembly of Sm(II) clusters which participate to various extents in cluster formation and THF cleavage.

Organometallic Complex Synthesis and CatalysisMetal complexes synthesis and propertiesMagnetism in coordination complexes