Advanced Materials

Cover image for Advanced Materials

June 1995

Volume 7, Issue 6

Pages fmi–fmi, 513–594

  1. Masthead

    1. Top of page
    2. Masthead
    3. Essay
    4. Articles
    5. Communications
    6. Research News
    1. Masthead (page fmi)

      Version of Record online: 15 SEP 2004 | DOI: 10.1002/adma.19950070601

  2. Essay

    1. Top of page
    2. Masthead
    3. Essay
    4. Articles
    5. Communications
    6. Research News
    1. Materials technology in automotive recycling (pages 513–518)

      Dr. Arnulf Frisch and Dr. Claus Razim

      Version of Record online: 15 SEP 2004 | DOI: 10.1002/adma.19950070602

      The growing number of dissed cars and the resulting amount of waste contribute to the increasing pressure on disposal sites. The materials selection for, and the design of, new motor veicles are influenced by teh need to reuse the constituent materials. The current situation often involves shredding old vehicles and sorting the resulting mixture of materials before disposing of a large proportion of the remainder on a dump. The possibilities for the future, including a new concept developed by Mercedes Bez involving the reuse of the energy potential of the materials, is dscussed.

  3. Articles

    1. Top of page
    2. Masthead
    3. Essay
    4. Articles
    5. Communications
    6. Research News
    1. Polymeric Electro-Optic Modulators: Matereials synthesis and processing (pages 519–540)

      Prof. Larry R. Dalton, Dr. Aaron W. Harper, Dr. Bo Wu, Dr. Rima Ghosn, Dr. Joyce Laquindanum, Dr. Ziyong Liang, Dr. Andrea Hubbel and Dr. Chengzeng Xu

      Version of Record online: 15 SEP 2004 | DOI: 10.1002/adma.19950070603

      The commercialization of new NLO materials will depend not only on the mastery of the technical problems but also on the availability of investment capital. Here, the research issues most relevant to commercialization are viewed and the advantages and disadvantages of new systems, both inorganic and organic, for example the cross-linked thin-film structure shown in the figure, presented and discussed.

  4. Communications

    1. Top of page
    2. Masthead
    3. Essay
    4. Articles
    5. Communications
    6. Research News
    1. Microcavity effect in a single-layer polymer light-emitting diode (pages 541–544)

      Dr. Hermann F. Wittmann, Dr. Johannes Grüner, Prof. Richard H. Friend, Dr. George W. C. Spencer, Dr. Steve C. Moratti and Dr. Andrew B. Holmes

      Version of Record online: 15 SEP 2004 | DOI: 10.1002/adma.19950070604

      The luminescence of conjugated polymers is of great interest both as a tool for the investigation of electronic processes in these materials and ecause of its significance for applications in light-emitting devices. The first demonstration of an electroluminescence-pumped microcavity using a conjugated polymer is reported, representing the first step towards the development of an electrically or optically pumped organic laser.

    2. Unsaturated ladder polymers: Structural variations and improved molecular weights (pages 544–546)

      Benediki Schlicke, Heike Schirmer and Prof. Arnutlf-Dieter Schlüter

      Version of Record online: 15 SEP 2004 | DOI: 10.1002/adma.19950070605

      All-carbon ladder polymers with extended π systems are of interest for electroluminescence and photovoltaics applications. The synthesis of two new ladder polymers (e.g. see Figure) exhibiting relatively high molecular weights and pronounced film-forming abilities, is reported. It is also shown that the degree of saturation in these polymers can be chemically closly controlled.

    3. An oligothiophene cation radical that forms π-stacks: A model for polaron aggregation in conducting polymers (pages 547–548)

      Prof. Larry L. Miller, Dr. Yuan Yu, Dr. Esmir Gunic and Dr. Robert Duan

      Version of Record online: 15 SEP 2004 | DOI: 10.1002/adma.19950070606

      A new class of functional units for preparing charge transfer salts, based on π-stacks of a conducting oligomer in analogy to the well-known stacks of TTF units, is reported and provides a connection between CT salts and conducting polymers. The synthesis of the new water-soluble thiophene oligomer is presented and it is suggested that π-stacks may be present in some oxidized polythiophenes and similar polymers.

    4. Chemical imaging by scanning force microscopy (pages 549–551)

      Dr. Sabri Akari, Dr. Dieter Horn, Dr. Harald Keller and Dr. Wolfgang Schrepp

      Version of Record online: 15 SEP 2004 | DOI: 10.1002/adma.19950070607

      The chemical imaging of surfaces with high lateral resolution i.e. the chemical identification of the materials which make up the surface was recently reported by Lieber et al. in Science. Here, work carried out partially in parallel using chemically modified SFM tips (see Figure) confirms the power of the technique and emphasizes its use for technical surfaces which normally show little contrast in SFM.

    5. Efficient two layer leds on a polymer blend basis (pages 551–554)

      Dr. Jörn Pommerehne, Dr. Horst Vestweber, Dr. Werner Guss, Dr. Rainer F. Mahrt, Prof. Heinz Bässler, Dr. Michael Porsch and Prof. Jörg Daub

      Version of Record online: 15 SEP 2004 | DOI: 10.1002/adma.19950070608

      Polymer blends in organic LEDs offer the advantage of processibility coupled with flexibility with respect to the chromophores which can be incorporated into their structures. The polymer matrix is also though to have a positive effect on the quantum efficiency and other LED performance indicators. Two-layer devices have also been shown recently to yield improved performances. Here, a two-layer device based on polymer blends is reported.

    6. Rectifying properties and photoconductivity of tetraruthenated nickel porphyrin films (pages 554–559)

      Prof. Koiti Araki, Lúcio Angnes and Henrique E. Toma

      Version of Record online: 15 SEP 2004 | DOI: 10.1002/adma.19950070609

      Oxidation-state selective modified electrodes based on tetraruthenated nickel porphyrin (see Figure) thin films are reported. The films are prepared by dip coating and are highly homogeneous and adherent, exhibiting a well-controlled electrochemical and photoelectrochemical response. The films simulate a rectifying junction.

    7. Bright blue electroluminescence from an oxadiazole-containing copolymer (pages 559–561)

      Dr. Qibing Pei and Dr. Yang Yang

      Version of Record online: 15 SEP 2004 | DOI: 10.1002/adma.19950070610

      Blue electroluminescence from a copolymer containing oxadiazole units is reported. The copolymer is separated in the light emitting diode device from the ITO anode by an additional layer of polyaniline in order to increase the quantum efficiency, resulting an external quantum efficiencies of 0.1%, and an intensity of the blue emitted light of 40 cm/m2.

    8. Triplet radical pairs of 3-carboxyproxyl encapsulated in a dendritic box (pages 561–564)

      Prof. E. W. Meijer, Dr. Johan F. G. A. Jansen, Dr. René A. J. Janssen, Dr. Ellen M. M. de Brabandero-van den Berg and Prof. E. W. Meijer

      Version of Record online: 15 SEP 2004 | DOI: 10.1002/adma.19950070611

      The encapsulation of small molecules inside a dendrimeric “box” has recently been reported. Here, the encapsulation and mobility of triplet radical moieties is described. For “boxes” (e.g. see Figure) containing two or more radicals the intermolecular ferromagnetic alignment of the encapsulated radicals to triplet state radical pairs is observed.

    9. Dielectric relaxation processes in an antiferroelectric liquid crystal (pages 564–568)

      Prof. M. Rosario de la Fuente, Santos Merino, Dr. Yolanda González, Miguel A. Pérez Jubindo, Dr. Blanca Ros, Dr. José A. Puértolas and Miguel Castro

      Version of Record online: 15 SEP 2004 | DOI: 10.1002/adma.19950070612

      The dielectric properties in a liquid crystal exhibiting ferro, ferri, and antiferroelectric mesophases have been studied. The dielectric response, although complex, allows the characterization of teh various phase transitions in the material. The modes corresponding to the antiferroelectric mesophases are found to be particularly complex and cannot be interpreted on the basis of previously published theories.

    10. Lateral deposition of polypyrrole lines over insulating gaps. Towards the development of polymer-based electronic devices (pages 568–571)

      Christine Kranz, Markus Ludwig, Prof. Herrmann E. Gaub and Dr. Wolf Gang Schuhnrann

      Version of Record online: 15 SEP 2004 | DOI: 10.1002/adma.19950070613

      Molecular wires connecting gold electrodes separated by a 100 μm insulating gap (see Figure) have been produced using a novel method for the microstructured deposition of polypyrrole lines on conducting substrates. The scanning electrochemical microscope used to deposit the lines is described and a microelectrochemical transitor produced using the technique presented.

    11. Polyalkylthiophenes as electrochromic materials: A comparative study of poly(3-methylthiophenes) and poly(3-hexylthiophenes) (pages 571–574)

      Dr. Catia Arbizzani, Porf. Alessandro Bongini, Porf. Marina Mastragostino, Dr. Alberto Zanelli, Dr. Giovanna Barbarella and Massimo Zambianchi

      Version of Record online: 15 SEP 2004 | DOI: 10.1002/adma.19950070614

      Tuning of the undoped–doped color contrast can be obtained in poly(3-hexylthiophenes) through the electropolymerization of oligomers of different length and regiochemistry. The regiochemistry affects the optical properties of the materials and molecular design allows the production of complementary electrochromic materials for variable light transmission devices.

    12. A new class of electron transport compounds: 1,3-bis-dicyanomethylene indanes (pages 574–576)

      Johan Rommens, Prof. Mark van der Auweraer, Frans C. De Sclryver and Dr. Paul M. Borsenberger

      Version of Record online: 15 SEP 2004 | DOI: 10.1002/adma.19950070615

      Electron transport layers, comprised of polymers doped with electron acceptor compounds have proved difficult to develop as teh inclusion of the acceptors generally results in poor solubility in coating solvents, limited miscibility and even toxic properties. The title compounds (see Figure) are soluble, miscible with a wide range of polymers, and show essentially to absorption in the visible region of the spectrum.

    13. Photo-induced cross-linking of poly(ethynyl)carbosilane fibers in the solid state: New insights on the application of atomic force microscopy (pages 576–578)

      Prof. Stephen E. Johnson, Homan Mostafavi, Jay Rahman and Prof. Kevin J. Thorne

      Version of Record online: 15 SEP 2004 | DOI: 10.1002/adma.19950070616

      The cross-linking of carbosilane polymers is part of the process used to produce silicon carbide fibers. AFM observations of the photo-induced reactions occurring on the surface of the materials during the cross-linking process reveal substantial material transport during the phase transformations. It is also reported that the cross-linking occurs through the ethynyl and hydrosilyl moieties of the title materials. The AFM also allows the study of the details of the reactions as the information obtained is not averaged out as in other surface analytical techniques.

    14. Unconventional mesogens of hyperbranched amides and corresponding ammonium derivatives (pages 578–581)

      Uwe Stebani and Dr. Gunter Lattermann

      Version of Record online: 15 SEP 2004 | DOI: 10.1002/adma.19950070617

      A cyclic core is not essential for mesomorphism. But just how flexible, or “open” can be central units in a branched compound be before liquid crystallinity is no longer exhibited? Here, the influence on the substitution patterns and in particular of hydrogen bonding in the title compounds is examined and it is found that protonation of some of the less-substituted compounds is required in order to impart the required degree of rigidity.

  5. Research News

    1. Top of page
    2. Masthead
    3. Essay
    4. Articles
    5. Communications
    6. Research News
    1. Graphene in 3-dimensions: Towards graphite origami (pages 582–586)

      Dr. Thomas W. Ebbesen and Dr. Hidefumi Hiura

      Version of Record online: 15 SEP 2004 | DOI: 10.1002/adma.19950070618

      The systematic construction of graphite structures (for example see Figure and Cover picture) is within reach. These structures are formed accidentally on the surface of HOPG graphite due to the friction exerted by the tip of an atomic force microscope but could also be designed “to order”. The origin of the structures and various approaches for their design are discussed.

    2. Reversible photoisomerizable monolayers for the transduction of optical signals (pages 587–589)

      Prof. Itamar Willner and Dr. Bilha Willner

      Version of Record online: 15 SEP 2004 | DOI: 10.1002/adma.19950070619

      Bioelectronic devices based on te photostimulation of the chemical and physical properties of molecules are presented. Assemblies consisting of photoswitchable biomaterials and conducive interfaces have opened new avenues in the design of architectures for molecular devices. Photosensitive self assembled monolayers on electrode surfaces provide the means for the nanoscale design of optoelectronic systems for information storage and processing, signal amplification, and biosensor devices. Recent progress in the area is reviewed.

    3. Molecular organization of bacterio- rhodopsin films in optoelectronic devices (pages 590–594)

      Dr. Koichi Koyama, Dr. Naoto Yamaguchi and Dr. Tsutomu Miyasaka

      Version of Record online: 15 SEP 2004 | DOI: 10.1002/adma.19950070620

      Bacteriorhodopsin (bR) is a protein with a molecular weight of 26 000 found in the plasma membrane of Halobacterium sarinarium. The versatile optical functions of bR, especially when it is organized in oriented membranes, make it a material of potential interest for the development of intelligent optoelectronic devices. Recent progress in the orientation of the bR moieties and in the application of the oriented structures in devices is reviewed.