Advanced Materials

Cover image for Advanced Materials

Mai 1997

Volume 9, Issue 5

Pages fmi–fmi, 373–446

  1. Masthead

    1. Top of page
    2. Masthead
    3. Editorial
    4. Articles
    5. Communications
    6. Research News
    7. Book Reviews
    8. Conference Calendars
    1. Masthead (page fmi)

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090501

  2. Editorial

    1. Top of page
    2. Masthead
    3. Editorial
    4. Articles
    5. Communications
    6. Research News
    7. Book Reviews
    8. Conference Calendars
    1. You have free access to this content
      Guiding european materials science (page 373)

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090502

  3. Articles

    1. Top of page
    2. Masthead
    3. Editorial
    4. Articles
    5. Communications
    6. Research News
    7. Book Reviews
    8. Conference Calendars
    1. Phasmids and Polycatenar Mesogens (pages 375–388)

      Dr. Huu-Tinh Nguyen, Prof. Christian Destrade and Dr. Jacques Malthécte

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090503

      Polycatenar mesogens have a shape intermediate between classical rod-like and disc-like liquid crystals which allows practically all the mesomorphic symmetrics to be obtained with the same molecular core by varying the temperature or the number and position of grafted chains (see Figure: R = H(CH2)nO). The synthesis, mesomorphic properties, and structures of polycatenar mesogens are reviewed, with emphasis on the structure–properties relationship.

  4. Communications

    1. Top of page
    2. Masthead
    3. Editorial
    4. Articles
    5. Communications
    6. Research News
    7. Book Reviews
    8. Conference Calendars
    1. Improved field-effect mobility in short oligothiophenes: Quaterthiophene and quinquethiophene (pages 389–391)

      Dr. Riadh Hajlaoui, Prof. Gilles Horowitz, Dr. Francis Garnier, Dr. Alexandre Arce-Brouchet, Dr. Laurent Laigre, Dr. Ahmed El Kassmi, Dr. Frédéric Demanze and Dr. Fayçal Kouki

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090504

      Organic field effect transistors (OFETs) made from quaterthiophene (4T) and quinquethiophene (5T) have been fabricated with greatly enhanced field-effect mobilities. It is shown that the problem seems to lie in achieving efficient charge injection rather than in poor charge transport within the material. Dopping of the drain and source contacts with a thin layer of the electron acceptor TCNQ is demonstrated to improve charge injection in 4T devices. Other factors affecting performance are considered briefly.

    2. Microlithographic process for patterning conjugated emissive polymers (pages 392–395)

      Michelle L. Renak, Prof. Guillermo C. Bazan and Dr. Daniel Roitman

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090505

      The spatially confined synthesis of emissive conjugated polymers—compatible with existing 1C fabrication technology—is described, which can be used to create well-defined micrometerscale patterned organic LEDs (see cover). The Figure shows the first step in the photolithographic process, which is followed by irradication, to produce a latent image, and development, resulting in patterned polymer.

    3. Measurements of optical electric field intensities in microcavities using thin emissive polymer films (pages 395–398)

      Seamus E. Burns, Dr. Nicola Pfeffer, Dr. Johannes Grüner, Dr. Marcus Remmers, Dr. Thomas Javoreck, Prof. Dieter Neher and Prof. Richard H. Friend

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090506

      The behavior of chromophores in microcavities—Fabry-Perot resonators with thickness of the order of the wavelength of light that are introduced into light-emitting devices to improve performance—is reported. Strong modification of the absorption and the spontaneous emission rates of the chromophores is demonstrated for thin luminescent layers of polyphenylene derivatives placed at different positions in the cavities. The technique of measurement is detailed and the implications of the results are discussed.

    4. Poly(propyleneimine) dendromesogens with hexagonal columnar mesophase (pages 398–403)

      Dr. James H. Cameron, Andreas Facher, Günter Lattermann and Siegmar Diele

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090507

      Dendritic mesogens—dendrimers that form mesophases—are the third group of liquid crystalline polymers (LCPs), following main-chain and side-chain LCPs. The synthesis of a series of different generations of dendromesogens (see Figure) is reported and their thermal behavior, molecular shape, and the textures observed by polarizing microscopy described. The role of hydrogen bonds in the formation of such mesophases is discussed.

    5. Electrochemical redox behavior and electroluminescence in the mixed energy-sufficient system thianthrene and 2-(4-Biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (pages 403–407)

      Silvia Janietz and Armin Wedel

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090508

      Efficient use of organic compounds in electroluminesent devices requires detailed knowledge of their redox potential values and their ability to form stable radical ions, information available from electrochemical investigations. The electrochemical behavior of the title compounds (TH and PBD) is described, followed by the preparation of light-emitting diodes (LEDs) based on them. The characteristics of mixed single-layer and separated double-layer devices presented here suggested that PBD and TH could be used for the construction of LEDs.

    6. Elastomeric light valves (pages 407–410)

      Dr. Dong Qin, Dr. Younan Xia and Prof. G. M. Whitesides

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090509

      Two types of elastomeric light valves, their fabrication, performance, and application, are described. Both are thin blocks of poly(dimethylsiloxane), PDMS, with relief structures on their surfaces, either an array of square pyramids or an array of retroreflective corner cubes (see Figure). Use of the valves in a display device is demonstrated, in which the transparency can be controlled by mechanical compression.

    7. 3D organized self-assembled monolayer electrodes: A novel biosensor configuration (pages 410–413)

      Srinivasan Sampath and Prof. Ovadia Lev

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090510

      A leak-free, reagentless biosensor for glucose is demonstrated as one application of the bulk modified electrode with three-dimensional self-assembled monolayers reported here. The preparation of the electrode and the electrochemical investigations of its behavior are described. It is shown that model enzymes can be incorporated in these materials so that the biomolecules retain their activity and the SAMs their dense structure and charge-mediation properties. A range of electrochemical applications are foreseen for such electrodes.

    8. Synthesis of nanometer-scale silver crystallites via a room-temperature electrostatic spraying process (pages 413–417)

      Dr. Peter J. Hull, Dr. John L. Hutchison, Dr. Oleg V. Salata and Prof. Peter J. Dobson

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090511

      Thin films of silver nanoparticles have been prepared by a room temperature electrospraying technique—the apparatus is shown schematically in the Figure. The characterization of the particles by optical absorption spectroscopy and high-resolution transmission electron microscopy is described. The behavior is compared with theory and a tentative mechanism proposed for the reduction of the silver.

    9. Room temperature silicon wafer bonding with ultra-thin polymer films (pages 417–420)

      Dr. Gertrud Kräuter, Andreas Schumacher, Ulrich Gösele, Thomas Jaworek and Prof. Gerhard Wegner

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090512

      Bonding of silicon wafers is required in microelectronics fabrication, for example. A room-temperature bonding process that leads to sufficient bond strength is necessary for bonding semi-processed wafers, i.e., those already containing temperature-sensitive structures. The room-temperature bonding of hydrophobic wafers is reported for the first time, an ultra-tin Langmuir-Blodgett film of a “hairy” rod-like polymer being used as an intermediate layer. The effect of the polymer layer on the surface roughness is investigated and possible directions o future work are indicated.

    10. Sequential gas-phase formation of Al2O3 and SiO2 layers on aerosol-made TiO2 Particles (pages 420–423)

      Dr. George P. Fotou and Prof. Toivo T. Kodas

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090513

      Barrier alumina-silica bilayers coated on titania aerosol particles (see Figure) may allow titania pigment with improved properties to be manufactured—e.g., the coatings protect the particles from sunlight. A single-step coating process is presented and coating pathways for silica and alumina proposed. The characterization of the particles is described and key parameters controlling the morphology of the coating layers discussed.

    11. An alternative design strategy for thin photorefractive polymer structures (pages 423–426)

      Prof. Fernando Agulló-López, Dr. Mercedes Carrascosa and Dr. María Aguilar

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090514

      Optimization of polymer photorefractive materials is complicated in conventional devices because the photorefractive material usually contains both a charge photosensitizer and a nonlinear chromophore and optimization can lead to compatibility problems. In the device design presented here, the photoconductive and electrooptic components are separated, allowing them to be optimized individually. The design strategy is described and analyzed theoretically. Its limitations are pointed out and example measures of performance given.

    12. Preserving a globular protein shape on glass slides: A self-assembled monolayer approach (pages 426–429)

      Zhihno Yang and Hyuk Yu

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090515

      The manufacture of low-cost, protein-friendly, biocompatible materials is important for biomedical applications. A method is presented for making glass surfaces—on which the globular protein shape is often lost –benign to proteins by covalently grafting relatively short poly((ethylene glycol)) chains (functionalized with trimethylsilane, see Figure), which form a brush-like self-assembled monolayer.

  5. Research News

    1. Top of page
    2. Masthead
    3. Editorial
    4. Articles
    5. Communications
    6. Research News
    7. Book Reviews
    8. Conference Calendars
    1. Mesoporous materials by templating of liquid crystalline phases (pages 431–436)

      Christine G. Goltner and Markus Antonietti

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090516

      The first mesoporous materials (pore diameter between 20 and 100 Å) were discovered just five eyars ago. A new approach to mesoporous materials by direct templating of lyotropic liquid crystals is reviewed and compared with strategies reported previously. The direct templating method is shown to be very verstile. It is suggested that the resulting materials can almost be termed “second generation” mesoporous materials, mesoporous materials, owing to the broad variety of mesoporous structure and size, high degree of ordering, and low incidence of defects.

    2. Nanofibers (pages 437–439)

      Guojun Liu

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090517

      The preparation of nanofibers—fibers with nanometer diameters—is briefly reviewed. Particular attention is paid to the synthesis based on locking-in the mesophasic structures formed by diblock copolymers. Examples of the resulting nanofibers with a core-shell structure (prepared for transmission electron microscopy by a freeze-drying method) are shown in the Figure.

  6. Book Reviews

    1. Top of page
    2. Masthead
    3. Editorial
    4. Articles
    5. Communications
    6. Research News
    7. Book Reviews
    8. Conference Calendars
  7. Conference Calendars

    1. Top of page
    2. Masthead
    3. Editorial
    4. Articles
    5. Communications
    6. Research News
    7. Book Reviews
    8. Conference Calendars
    1. Conference Calendar (pages 444–446)

      Version of Record online: 29 OCT 2004 | DOI: 10.1002/adma.19970090524

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