Advanced Materials

Cover image for Advanced Materials

August 1995

Volume 7, Issue 8

Pages fmi–fmi, 687–762

  1. Masthead

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

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19950070801

  2. Essay

    1. Top of page
    2. Masthead
    3. Essay
    4. Articles
    5. Communications
    6. Research News
    1. The national science foundation advanced materials and processing program (pages 687–690)

      Dr. Seymour J. Lapporte

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19950070802

      The national science foundation (NSF) has been providing support for materials science research since 1972. The interacting components making up NSF's Advanced Materials and Processing Program, which began initially as a federal initiative in 1993, are described. The goals, levels and modes of support are briefly discussed, whereby the importance of partnerships, particularly between university, industrial and government laboratories, is emphasized. The article concludes with a look into the future.

  3. Articles

    1. Top of page
    2. Masthead
    3. Essay
    4. Articles
    5. Communications
    6. Research News
    1. Substituted Rigid Rod-Like Polymers—Building Blocks for Photonic Devices (pages 691–702)

      Dr. Dieter Neher

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19950070803

      Substituted rigid rod-like polymers (RRPs) can be exploited to control the microscopic order in, and the fabrication of, devices with potential uses in photonics. The supermolecular structures formed by these interesting materials (e.g. see Figure) are considered, attention being focused on the correlation between structural properties and macroscopic properties such as nonlinear susceptibilities

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    2. Dielectrics for Field Effect Technology (pages 703–710)

      Dr. Pieter Balk

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19950070804

      The operaion of semiconductor devices is based on current control by means of electrically variable potential barriers. Dielectric materials such as SiO2, which can be produced simply through the thermal oxidation of a silicon substrate, and Si3N4 and Ta2O5, which offer higher dielectric constants, are used for such purpose, some also offering the opportunity to develop nonvolatile storage in capacitor structures. The applications of dielectric materials in field effect transitor and capacitor technology are reviewed.

  4. Communications

    1. Top of page
    2. Masthead
    3. Essay
    4. Articles
    5. Communications
    6. Research News
    1. Synthesis of AIPO4-5 aluminumphosphate molecular sieve crystals for membrane applications by microwave heating (pages 711–714)

      Dr. Irina Girnus, Dr. Marga-Martina Pohl, Dr. Jürgen Richter-Mendau, Dr. Matthias Schneider, Dr. Manfred Noack, Dr. Dieter Venzke and Dr. Jürgen Caro

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19950070805

      Aluminum phosphate molecular sieves with well-shaped hexagonal column-like morpholgoy (see Figure) have been produced by applying microwave heating to a gel. The crystals are effective materials for application in one-dimensional membranes for molecular sieving. As can be seen in the figure, crystals containing a central tubular void can also be produced

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    2. Photochemical fabrication of nonlinear optical polymer waveguides (pages 715–718)

      Dr. Iain McCulloch, Dr. George Boudoughian and Dr. Hong-Tai Man

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19950070806

      Waveguides based on methacrylate polymers containing active dinitrostilbene chromophores have been fabricated by photobleaching using a xenon lamp. The efficiency of photobleaching, as well as the effective refractive index changes obtainable, represent a singnificant improvement over currently used materials, single-mode waveguides being formed with a optical loss of less than 1 dB cm−1.

    3. Polar inclusion compounds of perhydrotriphenylene (phtp) and efficient nonlinear optical molecules (pages 719–721)

      Prof. Jürg Hulliger, Olaf König and Dr. Ralf Hoss

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19950070807

      Host lattices based on piperazines, which can include a large variety of linear “rod-shaped” π systems, are presented. One example is the inclusion of efficient nonlinear optical molecules (e.g. see Figure, and the cover picture this month) which leads to materials exhibiting attractive electro-optical properties

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    4. Photoelectron and optical spectroscopic investigations of the electronic structure of oligo(p-phenylenevinylene)s in the solid state (pages 722–726)

      Dr. Albert Schmidt, Michele L. Anderson, Darren Dunphy, Thomas Wehrmeister, Prof. Klaus Müllen and Prof. Neal R. Armstrong

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19950070808

      The performance of organic light-emitting diodes based, for example, on poly(p-phenylenevinylene) could be more easily optimized on the basis of a thorough knowldge of the energies of the electron affinities and the ionization potentials of the materials. Here, results from UV-photoelectron spectroscopy are presented which allow the determination of the absolute binding energies of the occupied molecular orbitals of oligo-PPV. These results are compared with values calculated using semiempirical methods.

    5. Synthesis of novel polymers containing cyclobutadiene thiophene and alkyne units: polymeric organometallic mesogens (pages 726–728)

      Markus Altmann, Dr. Volker Enkelmann, Dr. Günther Lieser and Dr. Uwe H. F. Bunz

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19950070809

      A new class of organometallic liquid-crystalline rigid-rod polymers containing thiophene (see Figure) are reported and it is shown how their phase behavior can be tuned through variation of the side groups. The crystallization of the compound shown in the Figure proceeds through a transient lyotropic smectic state, a state hitherto unknown in polymeric organometallic systems

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    6. Surface acoustic wave chemical microsensors based on covalently bound self-assembled host monolayers (pages 729–731)

      Louie W. Moore, Dr. Kendall N. Sprjnger, Jing-Xuan Shi, Dr. Xiaoguang Yang, Dr. Basil I. Swanson and Dr. Dequan Li

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19950070810

      Novel asymmetric cyclodextrin derivatives have been synthesized. The materials form self-assembled host monolayer thin films under the action of silane coupling reagents. Ultrasensitive (low-ppm) sensors for volatile organic compounds have been developed based on these and related materials, and it is suggested that pattern recognition with an array of such sensors could be a feasible approach to the identification of a particular organic material.

    7. Noble metal loaded block lonomers: micelle organization, adsorption of free chains and formation of thin films (pages 731–735)

      Joachim P. Spatz, Arno Roescher, Dr. Sergei Sheiko, Dr. Georg Krausch and Prof. Martin Möller

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19950070811

      Monitoring the formation of ultrathin films by scanning force microscopy provides information, for example, on the concentration dependence of the film structure (the Figure shows micelle agglomeration from high concentration solutions to form a layer with holes) and insight into the process from micelle formation to structural transformation in the films

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    8. Origins of the spontaneous magnetization in MnPS3 Intercalates: A Magnetic Susceptibility and Powder Neutron Diffraction Study (pages 735–739)

      Dr. John S. O. Evans, Dr. Dermot O'Hare, Prof. René Clement, Dr. Anne Leaustic and Dr. Pierre Thuéry

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19950070812

      A link between metal vacancy sites and magnetic ordering in the ion exchange intercalates of MnPS3 has been established. High-temperature X-ray pattersn show that the formation of a metal vacancy superstructure and the transition to the magnetically ordered state are intimately linked, providing strong evidence that spontaneous magnetization results from the imblanace of spins on the two sublattices of the antiferromagnetically ordered host lattice leading to net ferrimagnetism.

    9. Porous etching: A means to enhance the photoresponse of indirect semiconductors (pages 739–742)

      Dr. Ben H. Erné, Dr. Daniël Vanmaekelbergh and Prof. John J. Kelly

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19950070813

      A strategy for improving the photoresponse for junctions based on crystalline and polycrystalline semiconductors is presented. Porous etching is used to produce a layer (e.g., see Figure) within which the light is more effectively absorbed. By tailoring the porous layer, it is possible to ensure that the minority carriers, while generated deep within the semiconductor, are nevertheless able to reach the junction without recombining

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    10. Tunable electroluminescence and photoluminescence in phenylenevinylene-naphthylenevinylene copolymers (pages 742–745)

      Enez Z. Faraggi, Haim Chayet, Gil Cohen, Dr. Ronny Neumann, Prof. Yain Avny and Prof. Dan Davidov

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19950070814

      Color tuning of the electro- and photoluminescence from naphthalenevinylene–PPV–based light-emitting diodes between yellow-green and red is reported. Band structure considerations are employed to explain that chemical selectivity and selective band-gap tuning are observed in some of the copolymers studied but not in others. It is also found that light emission can be tuned by changing the thickness of the copolymer film in the LED.

    11. Single crystal ß-Si3N4 fibers obtained by self-propagating high temperature synthesis (pages 745–747)

      Dr. Miguel A. Rodriguez, Dr. Nikolay S. Makhonin, Juan A. Escriña, Dr. Inna P. Borovinskava, Dr. María I. Osendi, Dr. Maria F. Barba, Prof. Juan E. Iglesias and Prof. José S. Moya

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19950070815

      The growth of single crystal β-silicon nitride fibers (see Figure) several millimeters long through the application of self-propagating high-temperature synthesis is demonstrated. Advantages include the igh purity of the fibers obtained, the fact that the fibers are stable up to 2000°C, and the low cost of the SHS process

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    12. Nature and dynamics of radicals in polyaramide as studied by pulsed electron nuclear double resonance (pages 747–750)

      Axel Sammet, Dr. Michael Hubrich, Dr. Günter Maresch and Prof. Hans Wolfgang Spiess

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19950070816

      Chain scission is one of the factors which leads to the failure of high-performance materials based on main-chain liquid crystalline polymers. Stable radical species are formed wich can be studied using the ENDOR technique, thus throwing some light on the degradation mechanism, dynamics and kinetics in a range of commercial polymers

  5. Research News

    1. Top of page
    2. Masthead
    3. Essay
    4. Articles
    5. Communications
    6. Research News
    1. Mesomorphous polyelectrolyte-surfactant complexes (pages 751–753)

      Prof. Markus Antonietti, Dr. Christian Burger and Dr. Jochem Effing

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19950070817

      Polyelectrolyte–surfactant complexation allows the design and synthesis of a variety of highly ordered materials (sch as that modeled in the Figure). The variation of the polyelectrolyte and surfactant properties enables the tuning of the mechanical, electrical, and optical properties of the materials. The highly ordered media produced could be combined with a number of functional componentn (e.g., NLO dyes, conducting subunits, or gas selective groups)

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    2. 2-D. charge-transfer molecules for second order nlo: off-diagonal orientation (pages 754–758)

      Dr. Hari Singh Nalwa, Dr. Toshiyuki Watanabe and Prof. Seizo Miyata

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19950070818

      Second order nonlinear optical materials based on two-dimensional charge-transfer molecules rather than one-dimensional molecules offer a number of advantages. For example, the 2-D CT molecules retain their second order nonlinearity even if they are inclined away from normal to the substrate. This interesting class of new materials is presented and the factors influencing the performances of the materials, such as the incorporation of long π-conjugated segments into the molecules, are discussed.

    3. Electrochemically polymerizable self-assembled monolayers (pages 759–762)

      Robert J. Willicut and Prof. Robin L. McCarley

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19950070819

      Surface-confined monomer-containing monolayers based on pyrroles on an electrode offer the possibility for a high level of control over the electrochemical polymerization of the monomers within the monolayer. This is of importance for the development of molecular-scale electronic devices. The materials and the technique of surface-confined polymerization are presented.

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