Advanced Materials

Cover image for Advanced Materials

December 1996

Volume 8, Issue 12

Pages fmi–fmi, 957–1034

  1. Masthead

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

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19960081201

  2. Essay

    1. Top of page
    2. Masthead
    3. Essay
    4. Review
    5. Communications
    6. Research News
    1. The proposals to split-up Japan's NTT (pages 957–958)

      Prof. Masatomo Fujimoto

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19960081202

      The fate of researchers at NTT, Japan's telecommunications company, has been hanging in the balance since 1982, when the debate first began about whether to split-up NTT. The next decision is due in March 1997. Professor Fujimoto briefly traces the history of the debate and considers the possible consequences of a split: Would it encourage or discourage competitiveness? What would be the effect on long-term, fundamental research compared to short-term, product-oriented projects? The present organizational structure of NTT's R & D is outlined.

  3. Review

    1. Top of page
    2. Masthead
    3. Essay
    4. Review
    5. Communications
    6. Research News
    1. The design and synthesis of Heterogeneous Catalyst Systems (pages 959–968)

      Dr. Norman Herron and Dr. William E. Farneth

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19960081203

      A Maxwell's Demon approach to catalysis, in which individual molecules can be distinguished, has come closer to reality in recent years. Two new approaches to catalyst synthesis are described that are leading the way to catalyst design. The Figure shown n-octane proceeding through the 8-ring window of zeolite A toward the iron active site for oxidation. The relative size of the window and alkaline causes selectivity for oxidation towards the end of the chain.

  4. Communications

    1. Top of page
    2. Masthead
    3. Essay
    4. Review
    5. Communications
    6. Research News
    1. The interaction of poly (p-phenylenevinylene) with air (pages 971–974)

      Dr. Kezhao Xing, Dr. Mats Fahlman, Dr. Michael Lögdlund, Dr. Doni A. dos Santos, Dr. Vincent Parenté, Dr. Roberto Lazzaroni, Prof. Jean-Luc Brédas, Dr. Richard W. Gymer and William R. Salaneck

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19960081204

      The exposure of poly(p-phenylenevinylene), PPV, to air affects its performance in polymer-based light-emitting devices. An investigation is described in which exposure to air is demonstrated to give rise to reversible affects associated with the absorption of water vapor, leading to determinal changes in the outer electronic structure (see also the cover of this issue). In particular the resulting increase in torsion angle is shown to lead to a reduction in conjugation. A method of preparing clean PPV films is proposed.

    2. Laser action in poly (m-phenylenevinylene-co-2,5-dioctoxy-p-phenylenevinylene) (pages 974–978)

      Wolfgang Holzer, Prof. Alfons Penzkofer, Sung-Huan Gong, Dr. Andreas Bleyer and Prof. Donal D. C. Bradley

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19960081205

      The lasing action of a new conjugated copolymer in tetrahydrofuran (THF), xylene, toluene, and chloroform is reported. The title copolymer differs from many of the other conjugated copolymers that have been studied in that it includes meta-linked phenylene rings in its backbone (see Figure). The results presented—e.g., lasing threshold energy of 25 μJ, spectral halfwidth of 8 nm in THF, an expected wide tuning range—hold promise for the realization of solid state polymer lasers.

    3. Efficient green electroluminescent diodes based on poly (2-dimethyloctylsilyl-1,4-phenylenevinylene) (pages 979–982)

      Sung Tae Kim, Dr. Do-Hoon Hwang, Dr. Xiao Chang Li, Dr. Johannes Grüner, Prof. Richard H. Friend, Dr. Andrew B. Holmes and Dr. Hong Ku Shim

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19960081206

      An exceptionally high photoluminescene efficiency (60%) is reported for the title compound, a nwe, solution-processable derivative of PPV. It is shown that the compound can be used to make relatively efficient green electroluminescent diodes, and methods of further improving the efficiency of the device, e.g., incorporation of an electron-conducting, hole-blocking material, are described. Electroluminescence, photoluminescence, and UV-vis absorptioni spectra are presented, together with the I[BOND]V and light characteristics of the devices.

    4. Efficient blue-light emitting devices from conjugated polymer blends (pages 982–985)

      Jonas Birgerson, Prof. Koji Kaeriyama, Prof. Piotr Barta, Dr. Per Bröms, Dr. Mats Fahlman, Dr. Thomas Granlund and Prof. William R. Salaneck

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19960081207

      A polymer light-emitting device with an external quantum efficiency of 2%, one of the highest values in polymer-based devices reported to date, had been fabricated from a blend of PDHPT (see Figure) and PDPP (poly(2,5-diheptyl-2′,5′-dipentoxybiphenylene)). The optical properties of the polymers and the device are presented. A particularly important point is the processability of the active media.

    5. Imaging the structure of the p-n junction in polymer light-emitting electrochemical cells (pages 985–987)

      Dr. David J. Dick, Prof. Alan J. Heeger, Dr. Yang Yang and Dr. Qibing Pei

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19960081208

      Light-emitting electrochemical cells (LECs) offer a new approach to light-emitting devices fabricated from semiconducting polymers. The p-n junction formed in situ in an LEC through electrochemical doping has been imaged in the surface cell configuration by measuring the doping profile, the electric field profile within the junction, and the electroluminescence emission profile. The methods used are described and the results interpreted to provide a detailed picture of the structure of the p-n junction.

    6. Molecularly imprinted polymers for optochemical sensors (pages 987–990)

      Prof. Franz L. Dickert and Sylvia Thierer

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19960081209

      Molecular imprinting can be used to generate selective cavities—which are required for sensors—more easily than traditional synthesis. Polyurethanes with exactly adapted cavities, created by the evaporation of solvent vapors, are used to demonstrate the principle and also how the embedding of a dye enables optical detection to be employed. The Figure shows a polyurethane host with ethanol guest molecules.

    7. Thiophene-based conjugated oligomers and polymers with high electron affinity (pages 990–994)

      Dr. Hoang Anh Ho, Dr. Hugues Brisset, Dr. El Hadj Elandaloussi, Dr. Pierre Frère and Prof. Jean Roncali

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19960081210

      The control of the bandgap of thiophene-based polymers and oligomers has become an important topic in recent years. One strategy is the introduction of electron-withdrawing groups in particular positions in the conjugated chain. An extension of this strategy is reported here: the synthesis and electrochemical investigation (e.g., analysis of the electropolymerization behavior) of a new series of π-conjugated oligomers containing 3, 4, and 5 heterocycles and two CN groups at various positions of the ethylene linkage.

    8. A new method for the preparation of conductive polyaniline solutions: Application to liquid crystal devices (pages 994–997)

      Dr. Eli Harlev, Dr. Tamila Gulakhmedova, Dr. Ilia Rubinovich and Gentadi Aizenshtein

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19960081211

      Transparent “all-polymer” electrodes are promising candidates for applications in LCDs and LEDs and LEDs. A novel approach for making a new polyaniline-based polymer is described, efficient solubilization of the conductive from of polyaniline is reported, and use of the resulting conductive polymer solutions for LCDs demonstrated. The Figure shows a bent polymer-dispersed LCD with transparent “all-polymer” electrodes in the “on” (transparent) state.

    9. Novel vitrifiable liquid crystals as optical materials (pages 998–1001)

      Prof. Shaw H. Chen, Dr. Hongqin Shi, Brooke M. Conger, Dr. John C. Mastrangelo and Dr. Tersuo Tsutsui

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19960081212

      Vitrifiable liquid crystals (VLCs) have several advantages in optical applications: long-term mesomorphic stability, environmental durability, ease of processing into thin films, and the capability of large aperture. A generic approach is demonstrated for the molecular design of VLCs with an elevated glass-transition temperature, in which a subtle balance must be struck between order (LC mesomorphism) and disorder (glass). Selected samples are used to illustrate potential applications in the control of light polarization and polarized photoluminescence.

    10. Oligo(siloxane) rings and cages possessing nickel-containing liquid crystal side chains (pages 1001–1005)

      Dr. Isabel M. Saez and Dr. Peter Styring

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19960081213

      A liquid-crystalline coordination compound immobilized on an oligomeric superstructure free from cross-linking (see Figure) is reported for the first time. A highly versatile synthetic methodology is described that allows unsymmetrical, mono-functionalized, metal-containing liquid-crystalline coordination complexes to be prepared. Related materials may find uses as novel catalysts.

    11. Optical and structural properties of new discotic acrylates polymerized in the discotic nematic phase (pages 1005–1008)

      Christine D. Favre-Nicolin, Dr. Johan Lub and Dr. Paul van der Sluis

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19960081214

      Discotic liquid crystals can be used as optical compensation layers to improve the viewing angle of twisted nematic liquid crystal displays, for example. The in situ photopolymerization of newly synthesized acrylates is shown to result in oriented films with a negative birefringence. The transition temperatures, birefringence, and thermal stability were measured and the structure of the polymers was determined by wide-angle X-ray diffraction in order to explain the difference in optical properteis between various polymers.

    12. Oriented growth of molecular sieves on inorganic membranes (pages 1008–1012)

      Prof. Chih-Ning Wu, Prof. Kuei-Jung Chao, Prof. Tzeng-Guang Tsai, Dr. Yuan-Horng Chiou and Prof. Han-Chang Shih

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19960081215

      A molecular sieve film with vertically oriented and closely packed crystals has been prepared by a novel method. The Figure shows VAP4-5 (zeolite-like) crystals anchored inside the straight channel walls of an anodic alumina membrane. The novel method of synthesis is outlined and the effect of varying the growth conditions, e.g., temperature, solution dilution, chemical composition, reactant source, described.

    13. Purification and opening of carbon nanotubes via bromination (pages 1012–1015)

      Prof. Yao K. Chen, Prof. Malcolm L. H. Green, Prof. Julian L. Griffin, Dr. Jens Hammer, Dr. Rachel M. Lago and Dr. Shik C. Tsang

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19960081216

      The purification and opening of carbon nanotubes via bromination is reported. Refluxing raw cathodic soot containing a mixture of nanotubes, nanoparticles, and amorphous carbon in liquid bromine, followed by oxidation in air, is shown to yield 10–20; w/w pure and opened nanotubes. The role of bromine in the purification steps is discussed, based on the results of transmission electron microscopy, temperature programmed oxidation, X-ray diffraction, and X-ray photoelectron spectroscopy investigations.

    14. Microcontact printing with a cylindrical rolling stamp: A practical step toward automatic manufacturing of patterns with submicrometer-sized features (pages 1015–1017)

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

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19960081217

      Microcontant printing using self-assembled monolayers has been extended to the patterning of large areas by the introduction of a rolling elastomeric stamp (see Figure). The procedure is described and scanning electron microscope images of silver test patterns are presented. The ability to form large areas of micropatterns rapidly is important for potential applications in sensors, microelectrode arrays, consumer electronic systems, and supports for cell cultures.

    15. Self-organization of size-selected, nanoparticles into three-dimensional superlattices (pages 1018–1020)

      Dr. Laurence Motte, Dr. Françoise Billoudet, Dr. Emanuelle Lacaze and Prof. Marie-Paule Pileni

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19960081218

      Three-dimensional quantum dot superlattices with fcc structure have been formed using reverse micelles and self-organization of Ag2S nanocrystals. It is reported that the size distribution of the nanoparticles can be narrowed by a chemical treatment of the interface and by particle extraction from the micelles. The formation of well-defined tow- or three-dimensional ordered arrays is required for the development of new types of optical gratings, optical filters, antireflective surface coatings, data storage systems, and microelectronics.

    16. Gold particle generation by spray pyrolysis (pages 1020–1022)

      Prof. Diptarka Majumdar, Prof. Toivo T. Kodas and Howard D. Glicksman

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19960081219

      Phase-pure, micrometer-sized, spherical gold particles (see Figure) have been generated for the first time by spray pyrolysis of gold nitrate at temperatures well below the melting point of gold. The effects of reaction atmosphere, temperature, and residence time on the morphology of the final product are described. The resulting gold powder is shown to be suitable for a variety of microelectronics applications.

    17. Lamellar semiconductor–organic nanostructures from self-assembled templates (pages 1022–1025)

      Paul Osenar, Paul V. Braun and Prof. Samuel I. Stupp

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19960081220

      A templating synthesis of nanocomposite materials with lamellar morphology is described in which the unique structure of the polyol amphiphiles—leading to a highly stabilized lamellar mesophase—is exploited. The use of these mesophases in the formation of semiconducting–organic nanocomposites that copy the symmetry and spacing of the mesophase is demonstrated. It is suggested that the regular arrangement of organic and semiconducting components on the molecular length scale could lead to novel optoelectronic materials.

  5. Research News

    1. Top of page
    2. Masthead
    3. Essay
    4. Review
    5. Communications
    6. Research News
    1. Self-assembled wires and channels (pages 1027–1030)

      Dr. Cornelus F. van Nostrum

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19960081221

      Supramolecular wires and channels are one-dimensional molecular materials capable of transporting charge, etc. in a predefined direction. Examples are given of wires and channels that have been formed by self-assembly in the liquid-crystalline state or in solution, for example from alkoxy-substituted triphenylenes (see Figure; R = aliphatic chain), using various approaches. The underlying principles are stressed.

    2. Parallel patterning with nanochannel glass replica membranes (pages 1031–1034)

      Dr. Douglas H. Pearson and Dr. Ronald J. Tonucci

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19960081222

      Nanochannel glass replica membranes, a recent invention, can be used for parallel patterning of substrates, for example as a shadow mask in reactive ion etching. The preparation of the membranes—formed by physical vapor deposition on wafers that have been cut from bundles of two types of glass fibers that are repeatedly drawn down to the correct dimensions—their uses and their advantages are described. How the size, position, geometric pattern, and packing density of the voids in the membranes can be controlled to a high degree is outlined.

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