Advanced Materials

Cover image for Advanced Materials

Juli 1997

Volume 9, Issue 8

Pages fmi–fmi, 597–680

  1. Masthead

    1. Top of page
    2. Masthead
    3. Materials Forums
    4. Article
    5. Reviews
    6. Communications
    7. Research News
    1. Masthead (page fmi)

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090801

  2. Materials Forums

    1. Top of page
    2. Masthead
    3. Materials Forums
    4. Article
    5. Reviews
    6. Communications
    7. Research News
    1. Materials Forum (page 597)

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090802

  3. Article

    1. Top of page
    2. Masthead
    3. Materials Forums
    4. Article
    5. Reviews
    6. Communications
    7. Research News
    1. The UK research assessment exercise (pages 599–600)

      Prof. Jack Harris

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090803

      In the Research Assessment Exercise, carried out roughly every four years, each university department in the UK is given a “mark” according to research performance. In the recently announced 1996 results, the materials science and metallurgy departments did extraordinarily well, five scoring the top mark (5). A compilation of the results is presented.

  4. Reviews

    1. Top of page
    2. Masthead
    3. Materials Forums
    4. Article
    5. Reviews
    6. Communications
    7. Research News
    1. Aromatic Poly(1, 3, 4-Oxadiazoe)s as Advanced materials (pages 601–613)

      DR. Burkhard Schulz, DR. Maria Bruma and Prof. Ludwig Brehmer

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090804

      The specialized-performance polymers poly(arylene-1,3-oxadiazole)s—see Figure for an example—have high-value end uses based on their electronic, optical, and thermal properties. The syntheses, solid-state structure, properties, and applications of poly(arylene-1,3,4-oxadiazole)s are reviewed.

    2. B/C/N Materials Based on the Graphite Network (pages 615–625)

      Prof. Masayuki Kawaguchi

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090805

      New semiconductors and host materials are expected to be found among newly synthesized boron/carbon/nitrogen (B/C/N) materials based on the graphite network. The synthesis, structure, and properties of such materials, including solid solutions, more-ordered B/C/N hybrids, and compounds (e.g., BC3, C5N, BC2N, BC3N, BC4N, BC6N2H3), are reviewed. Particular attention is paid to their electrical properties, luminescenc characteristics, and intercalation chemistry, together with the application of B/C/N materials as a battery electrode matrix.

  5. Communications

    1. Top of page
    2. Masthead
    3. Materials Forums
    4. Article
    5. Reviews
    6. Communications
    7. Research News
    1. Multiplexing optical systems: Multicolor-bifluorescent-biredox photochromic mixtures (pages 627–630)

      DR. Gerasimos M. Tsivgoulis and Jean-Marie Lehn

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090806

      Optical memory systems that exhibit multiplexity and multifunctionality may allow high-density storage and multiple addressing and readout. In a first step towards such systems, it is shown that two-component mixtures of dithienylethene compounds (e.g., see Figure) can be switched reversibly between four different color states, using light as a trigger. The fluorescence of redox behavior increases the multiplexity (see front cover).

    2. Thermally responsive rigid polymer monoliths (pages 630–633)

      Eric C. Peters, DR. Frantisek Svec and Prof. Jean M. J. Fréchet

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090807

      A composite that changes its permeability with temperature–leading to the possibilites of a thermal gate, thermal valve, or thermal cotnrol of hydrophobicity/hydrophilicity–is reported. A method is described to modify the internal pore surface of rigid polymer moonoliths by grafting-on PNIPAAm, a temperature-responsive polymer. Isocratic hydrrophobic interaction chromatography of proteins is presented, which is a novel separation technique based on the changes in surface polarity (and thus adsorption) accompanying the temperature-induced phase transition of the grafted PNIPAAm.

    3. Structures and properties of MeDTDM salts (pages 633–635)

      Yohji Misaki, Masateru Taniguchi, Takeshi Miura, Hideki Fujiwara, Tokio Yamabe, Tadashi Kawamoto and Takehiko Mori

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090808

      Unsymmetric tetrathifulvalene (TTF) derivatives, especially when fused with 1,3-dithiol-2-ylidenes (DT-TTFs), have yielded a large number of metallic salts and even some superconductors. The synthesis and characterization of teh methyl-substituted DT-TTF MeDTDM (see Figure) are reported as part of the search for new superconductors, the conductivities and X-ray structure analysis of the new metallic salts being emphasized.

    4. Polyazulenes and Polybiazulenes: Chiroptical Switching and Electron Transfer Properties of Structurally Segmented Systems (pages 635–639)

      DR. Michael Porsch, DR. Gabriele Sigl-Seifert and Prof. Jörg Daub

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090809

      The characterization of polyazulenes is reported with regard to two main aspects. First, results of circular dichroism spectroelectrochemistry of a carbohydrate-modified azulene indicate that structural reorganization and chiroptical switching occur on oxidative doping. Second, the investigation of phenylene/azulene polymeric films with meta- or para-phenylenes as bridging units provides information about electron transport and shows that phenylenic bridging allows structurally separated electron-transfer-active subunits to be created within the polymeric chain.

    5. Oligophenylenevinylenes for light-emitting diodes (pages 639–643)

      DR. Theodore Goodson III, Wenjie Li, DR. Ali Gharavi and Prof. Luping Yu

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090810

      Details of the structure–property correlation in organic light-emitting diodes (LEDs) are reported for the oligophenylenevinylene (OPV) system. The electroluminescence (EL) characteristics of 6-OPV (n equals; 2 in the Figure) and 10-OPV (n equals; 4 in the Figure) are compared and an explanation is proposed for the shift and broadening of the EL spectra under different driving voltages.

    6. Self-Propagating High Temperature Synthesis of Hexagonal Ferrites MFe12O19 (M = Sr, Ba) (pages 643–645)

      Dr. Ivan P. Parkin, Gareth Elwin, DR. Luis Fernández Barquin, Quang T. Bui, Dr. Quentin A. Pankhurst, DR. Alexei V. Komarov and Dr. Yuri G. Morozov

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090811

      Hexagonal ferrites, materials widely used for permanent bard magnets, are currently commercially synthesized by multistep ceramic methods. Alternative routes are also multistep as well as being time-consuming and expensive. Teh self-propagating, high-temperature synthesis (SHS) presented here is convenient, quick, inexpensive, and single-step and it enables a range of ferrites, SrxBayFe12O19 (x + y equals; 1), to be prepared. The principles of SHS are briefly explained before the characterization of the reaction products, including their magnetic properties, is described.

    7. Magnetic field induced reversed (Negative) magnetization for electrochemically deposited Tc = 260 K Oxidized Films of Chromium Cyanide Magnets (pages 645–647)

      Wayne E. Buschmann, Dr. Scott C. Paulson, Dr. Charles M. Wynn, Mihai A. Girtu, Prof. Arthur J. Epstein, Prof. Henry S. White and Prof. Joel S. Miller

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090812

      Molecule-based magnets with high ordering temperaturesTc (above room temperature) include some mixed-oxide hexacyanometallates. The example studied here, Cr2.12(CN)6 · ½ H2O (the Figure shows its crystalline and amorphous phases), is shown to have Tc equals; 260 K and exhibit negative (reverse) magnetization. An explanation is suggested for this behavior and the temperature and field dependences of the magnetization.

    8. Crystallization of CaCO3 in the presence of PEO-block-PMAA copolymers (pages 647–651)

      Joanne M. Marentette, Jochen Norwig, Elnar Stöckelmann and Wolfgang H. Meyer

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090813

      How copolymers affect the crystallization of inorganic materials has been studied, using as an example the effect of poly(ethylene oxide)-block-poly(methacrylic acid) (PEO-bl-PMAA) on calcite (CACO3). It si shown that the presence of PEO-bl-PMAA can lead to a drastic alteration of the crystal habit of calcite, producing a different morphology as a result of the changed crystallization kinetics. It is hoped that this work will eventually lead to a high degree of control of crystallization in the laboratory, approaching that found in nature.

    9. Solvent-assisted microcontact molding: A convenient method for fabricating three-dimensional structures on surfaces of polymers (pages 651–654)

      DR. Enoch King, DR. Younan Xia, Xiao-Mei Zhao and Prof. George M. Whitesides

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090814

      Solvent-assisted micro-contact molding (SAMIM), a non-photo-lithographic technique for fabriation of patterned, quasi-three-dimensional structures on surfaces of many different polymers, is described. The basis of the technique–an embossing/molding process in which a solvent softens a polymer–is out lined and many examples are given. The Figure shows a polystyrene structure produced using SAMIM with acetone as the solvent.

    10. Effect of surface fractality on the permeability of transparent gas barrier coatings (pages 654–658)

      DR. Gema Garcfa-Ayuso, DR. Roberto Salvarezza, DR. Jos Ea M. Martinez-Duart, DR. Olga Sánchez and DR. Luis Vázquez

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090815

      The permeability of inorganic barrier coatings on polymers is important in applications in the flexible packaging industry, for exmaple. Relationships are reported between the film surface nanostructure, in particular the film pore surface fractality, and the permeability of water and oxygen molecules through different SiO2–Al2O3 films. Following a brief out-line of the various contributions to transport of gases through a porous solid, it is shown that water undergoes surface-mediated permeation, the permeability thus varying with the surface fractal dimension D, while oxygen does not.

    11. Synthesis of cellular inorganic films from self-organized Media (pages 658–662)

      DR. Dominic Walsh and Prof. Stephen Mann

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090816

      Cellular and honeycomb structures of inorganic materials are of interest for applications requiring, e.g., catalyst supports or heat-resistant membranes. The synthesis fo cellular films from solvent-extracted metal-ion-containing microemulsions (the Figure shows a resulting hollow spherical shell of calcium carbonate) is extended here to FeIII, MnIII/IV, and CoIII oxides. The preparation is detailed and the mechanism of formation discussed.

    12. Shell mimetics (pages 662–667)

      Prof. Geoffrey A. Ozin, Hong Yang, DR. Igor Sokolov and DR. Neil Coombs

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090817

      The synthesis of mesoporous silica sell-shapes, with spiral and gyroid forms and ornate surface designs (see the inside front cover for examples), is described. High-resolutioin SEM, TEM, and AFM were used to establish the spatial relationship between the bulk and surface mesosstructure and the overall morphpology of the shell mimies. The various stages in the growth of the shell-shapes are described, which create silicified shell forms with periodic mesopores but devoid of microcystalline order.

  6. Research News

    1. Top of page
    2. Masthead
    3. Materials Forums
    4. Article
    5. Reviews
    6. Communications
    7. Research News
    1. New low-dimensional solids: Tellurium-rich alkali metal tellurides (pages 669–675)

      Prof. William S. Sheldrick, DR. Michael Wachhold, DR. Stephane Jobic, Prof. Raymond Brec and DR. Enric Canadell

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090818

      Tellurium-rich alkali metal tellurides tend to contain defective square planer tellurium lattices as part of their structures, and band structure calculations show that these lattices could be low-dimensional metals with interesting properties. The crystal and electronic structure of several recently reported Te-rich alkali metal tellurides, such as Rb4–xSn4Te17 ( 0 ⩽ x ⩽ 1) shown in the Figure, are briefly reviewed.

    2. The crystallization of polar, channel-type inclusion compounds: Property-directed superamolecular synthesis (pages 677–680)

      Prof. Jürg Hulliger, DR. Peter Rogin, Andrea Quintel, Peter Rechsteiner, Olaf König and DR. Michael Wübbenhorst

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090819

      How can the efficiency of formation of polar materials be improved? The work presented ehre makes use of the concept of supramolecular synthons, resulting in an inclusion formation approach that produces a nearly four times higher yield of polar crystal structures than the crystallization of dipolar molecules alone. The xample of co-crystallization of racemic all-trans perhydrotriphenylene (PHTP) with linear acceptors or donors is analyzed, and it is suggested that thie “Property-directed” synthesis has a potentially high degree of predictability.

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