Advanced Materials

Cover image for Advanced Materials

1997

Volume 9, Issue 12

Pages fmi–fmi, 941–998

  1. Masthead

    1. Top of page
    2. Masthead
    3. Materials Forum
    4. Review
    5. Communications
    6. Research News
    7. Book Reviews
    8. Correction
    1. Masthead (page fmi)

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19970091201

  2. Materials Forum

    1. Top of page
    2. Masthead
    3. Materials Forum
    4. Review
    5. Communications
    6. Research News
    7. Book Reviews
    8. Correction
    1. Materials Forum (page 941)

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19970091202

  3. Review

    1. Top of page
    2. Masthead
    3. Materials Forum
    4. Review
    5. Communications
    6. Research News
    7. Book Reviews
    8. Correction
    1. Entrapment of biocatalysts in hydrophobic sol-gel materials for use in organic chemistry (pages 943–954)

      Prof. Manfred T. Reetz

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19970091203

      Lipases trapped in hydrophobic organic/inorganic materials result in chemically and thermally stable heterogeneous catalysts that display unusually high catalytic activities. The entrapment of lipases and other biocatalysts by sol-gel encapsulation is an interesting approach to enzyme immobilization, which has the aim of increasing enzyme activity in organic solvents. Investigations that have been carried out to optimize encapsulation and to characterize the lipase-containing gels are reviewed. Possible applications in organic synthesis are indicated.

  4. Communications

    1. Top of page
    2. Masthead
    3. Materials Forum
    4. Review
    5. Communications
    6. Research News
    7. Book Reviews
    8. Correction
    1. Soluble organosilicon micronetworks with spatially confined reaction sites (pages 955–958)

      Dr. Frank Baumann, Dr. Bernhard Deubzer, Dr. Michael Geck, Dr. Jochen Dauth, Dr. Sergio Sheiko and Prof. Manfred Schmidt

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19970091204

      Extremely small monodisperse micronetworks have potential applications as molecular containers or reaction vessels. The advantages of the sol-gel synthesis reported here, involving endcapping with Si-O-SiR3 groups, are pointed out and the characterization of the resulting spherical particles (radius between 5 nm and 20 nm), see Figure, is described. The variety of functional groups and the high density of potential reaction sites are stressed.

    2. Structural chemistry and guest inclusion of a new supramolecular material showing sensitivity to organic solvent vapors (pages 958–961)

      Dorit Meinhold, Dr. Wilhelm Seichter, Dr. Kurt Köhnke, Dr. Jürgen Seidel and Prof. Edwin Weber

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19970091205

      Clathrate formation—the formation of crystalline inclusion compounds—is one approach to chemical sensing of vapors and gases. The synthesis of a new diol host compound is described and absorptive clathrate formation and thermal clathrate decomposition are reported for acetone as the guest. It is shown that the sorptive uptake of a guest vapor by the crystalline host compound is not merely surface adsorption but true clathrate formation, involving a solid-state transformation. It is suggested that the use of the host as a chemical sensor is not far off.

    3. Unprecedented thermo- and ion-responsive behavior of a non-ionic water-soluble polysilane (pages 961–964)

      Dr. Thomas J. Cleij, Prof. Leonardus W. Jenneskens and Dr. Sebastiaan G. S. J. M. Kluijtmans

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19970091206

      Polysilanes display remarkable optical and electronic properties that are affected by teh degree of σ-conjugation, which depends on the conformation of the silicon backbone. The thermo- and ion-responsive behavior of aqueous solutions of 1 (Figure) is described, including «inverse» abrupt termochromism and the tunability of the lower critical solution temperature (LCST) by addition of inorganic salts.

    4. Direct determination of the emission zone in a polymer light-emitting diode (pages 964–968)

      Dr. Johannes Grüner, Dr. Marcus Remmers and Dr. Dieter Neher

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19970091207

      Many operating mechanisms of polymer light-emitting diodes (LEDs) are still not fully understood, among them the crucial step of recombination of oppositely charged carriers to form excitons. Questions related to this step are: What is the shape of the recombination zone and what is the quenching loss at the metal electrode layers? An investigation is reported in which the emission zone is directly determined by analyzing the polarization of teh electroluminescence. It is shown that exciton quenching near the electrodes is a crucial parameter for the overall device efficiency.

    5. Solid-state droplet laser made from an organic blend with a conjugated polymer emitter (pages 968–971)

      Dr. Magnus Berggren, Dr. Ananth Dodabalapur, Dr. Zhenan Bao and Dr. Richart E. Slusher

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19970091208

      Lasers based on organic materials have been produced with a wide range of resonator design and in a variety of geometries. A new strategy is presented for fabricating permanently near-spherical whispering gallery mode (WGM) lasers from a blend of PPV7 and PBD (see Figure) by a melting and resolidification process. The thresholds and quality factors of these resonators are estimated and discussed.

    6. A conjugated polymer-based voltage-regulator device (pages 972–974)

      Ana C. Arias, Prof. Ivo A. Hümmelgen, Alvaro Meneguzzi and Prof. Carlos A. Ferreira

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19970091209

      A voltage-regulator multilayer device based on teh conjugated polymer PAN (poly(5-amino-I-naphthol)) sandwiched between silver and tin oxide electrodes is reported. It is shwon that after breakdown at Vcrit the devices is self-regulatory, maintaining an approximately constant potential difference Vstab between the tin oxide and silver electrodes; Vcrit and Vstab depend on the polymer film thickness. The current–voltage characteristic is compared with that of another voltage regulator, the Zener diode.

    7. Room temperature growth of mesoporous silica fibers: A new high-surface-area optical waveguide (pages 974–978)

      Dr. Qisheng Huo, Dr. Dongyuan Zhao, Dr. Jianglin Feng, Dr. Kenneth Weston, Prof. Steven K. Buratto, Prof. Galen D. Stucky, Dr. Stefan Schacht and Prof. Ferdi Schüth

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19970091210

      High-quality, hexagonal phase, mesoporous silica fibers (see Figure) can be grown by the general procedure for one-step, two-phase, room temperature synthesis reported here. The silica fibers, which are 1–5 μm in diameter and up to 5 cm long, have excellent long-range order, a narrow pore size distribution, and a pore volume of up to 0.78 cm3/g. The birefringent fibers can be used as high-surface-area optical fibers.

    8. An alternative synthetic route to soluble polyetherimide derivatives with high second-order optical nonlinearity (pages 978–981)

      Prof. Kwang-Sup Lee, Dr. Ki-Jeong Moon, Han Young Woo and Prof. Hong-Ku Shim

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19970091211

      Processible polytherimide-based polymers that display nonlinear optical (NLO) activity are reported to have been synthesized by the Mitsunobu reaction, in which the polyimide structure is synthesized directly in a single step from a diimide and a diol, without a high-temperature thermal imidization step. The resulting polymers, with pendant-incorporated tricyanovinyl azobenzene chromophores, showed very large second-order NLO activity with good temporal and thermal stability—in one case no decay of the signal was observed up to 125°C.

    9. Design of strongly NLO-active molecularly-based ferromagnets (pages 981–984)

      Dr. Sophie Bénard, Dr. Pei Yu, Dr. Thibaud Coradin, Dr. Eric Rivière, Dr. Keitaro Nakatani and Prof. René Clément

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19970091212

      Molecule-based ferromagnets that exhibit strong second-harmonic generation (SHG) are presented here for the first time. The strategy for producing such materials—replace the “innocent” bulky cations (C) in the C[M′M(ox)3] family of bimetallic magnets (M′ is e.g. Mn and M = CrIII or FeIII; the Figure shows the structure) by hyperpolarizable cationic chromophores—is described and X-ray, magnetic, and SHG results are reported.

    10. Magnetic molecular metals based on the organic donor molecule BET (BET = Bis(ethylenethio)tetrathiafulvalene): The series BET2[MCI4] (M3⊕ = Ga, Fe) (pages 984–987)

      Prof. Eugenio Coronado, Prof. Lawrence R. Falvello, José R. Galán-Mascarós, Carlos Giménez-Saiz, Dr. Carlos J. Gómez-García, Dr. Vladimir N. Lauhkin, Aaron Pérez-Benítez, Dr. Concepció Rovira and Prof. Jaume Veciana

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19970091213

      The molecular metals BET2[MCl4] with M = Fe, Ga (see article title for BET) have been prepared and their structural, transport, and magnetic properties investigated. It is shwon that the conducting layers of the organic donor BET are interleaved by the inorganic ions, which are fairly well isolated from each other in the crystal. However, in the case of the Fe, the ions are found not to be magnetically isolated but coupled by exchange interactions. A mechanism is suggested to account for the observed Fe–Fe interaction in this magnetic molecular metal.

    11. Weathering investigation of PVC coatings on iron sheets by the NMR MOUSE (pages 987–989)

      Dr. Gisela Zimmer, Andreas Guthausen, Udo Schmitz, Dr. Koji Saito and Prof. Bernhard Blümich

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19970091214

      A new kind of MOUSE–the NMR mobile universal surface explorer–makes NMR investigations possible on composites with ferromagnetic components, which were previously excluded from such studies, because inhomogeneous magnetic fields are used in the first place. An example application is described, to relaxation measurements of polyvinylchloride (PVC) coatings on iron sheets. It is demonstrated that new and artificially weathered PVC coatings can be distinguished by means of their different transverse relaxation times.

  5. Research News

    1. Top of page
    2. Masthead
    3. Materials Forum
    4. Review
    5. Communications
    6. Research News
    7. Book Reviews
    8. Correction
    1. Photorefractive materials for holographic interferometry (pages 991–993)

      Stefan Schloter and Prof. Dietrich Haarer

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19970091215

      The photorefractive properties of polymers for holographic interferometry are currently often better than those of their inorganic counterparts. The theory of the photorefractive effect is briefly outlined before the relevant experimental techniques and chemical approaches are reviewed. Applications are mentioned, for example the possibility of visualizing vibrations as a fringe pattern (see Figure).

  6. Book Reviews

    1. Top of page
    2. Masthead
    3. Materials Forum
    4. Review
    5. Communications
    6. Research News
    7. Book Reviews
    8. Correction
  7. Correction

    1. Top of page
    2. Masthead
    3. Materials Forum
    4. Review
    5. Communications
    6. Research News
    7. Book Reviews
    8. Correction
    1. You have free access to this content
      Correction (page 998)

      Article first published online: 29 OCT 2004 | DOI: 10.1002/adma.19970091220

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