Advanced Materials

Cover image for Advanced Materials

August, 1998

Volume 10, Issue 11

Pages 827–890

    1. Soft and Wet Materials: Polymer Gels (pages 827–837)

      Yoshihito Osada and Jian-Ping Gong

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199808)10:11<827::AID-ADMA827>3.0.CO;2-L

      The unique electrical, thermal, and chemical responses of polymer gels—elastic crosslinked networks in which the interstitial spaces are filled with a fluid—are reviewed. The movements of a chemomechanical gel, such as the shape memory phenomenon illustrated in the Figure, are shown to be “gentle” and “flexible” and reminiscent more of muscle than of metallic mechanical systems.

    2. STM Investigations of Thiol Self-Assembled Monolayers (pages 839–842)

      Andreas H. Schäfer, Christian Seidel, Lifeng Chi and Harald Fuchs

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199808)10:11<839::AID-ADMA839>3.0.CO;2-9

      The most-studied thin organic monolayers—which have applications in many areas of science and technology—are self-assembled monolayers (SAMs) of alkanethiols. Scanning tunneling microscopy (STM) of alkanethiol SAMs on Au(111) surfaces reveals small holes or defects, whose origin is a current topic of discussion. The STM investigation reported here of thiosalicylic acid on Au(111) reveals not holes but disordered structures. Comparison of the two sets of measurements provides new aspects for consideration with regard to the origin of the hole defects in thiol selfassembled films.

    3. Multilayered Langmuir–Blodgett Films of Thiol-Substituted Ultrasmall Gold Clusters (pages 842–845)

      Marko Burghard, Günther Philipp, Siegmar Roth, Klaus von Klitzing, Raphael Pugin and Günter Schmid

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199808)10:11<842::AID-ADMA842>3.0.CO;2-X

      Langmuir–Blodgett (LB) deposition of thiol-stabilized gold clusters is reported to be controllable through the action of a hydrophilic thiol in the subphase, leading to reproducible monolayer transfer. The Figure is a schematic representation of a gold cluster, denoted Au55SiOS and prepared from a precursor by ligand exchange with a oligosilsesquioxane-based thiol derivative, with 12 thiol molecules in the ligand shell.

    4. Synthesis of Layered Platinum-Based Materials Through Thermal Decomposition of Self-Assembled Metal Carbonyl–Surfactant Phases (pages 846–849)

      Timothy Bell and David M. Antonelli

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199808)10:11<846::AID-ADMA846>3.0.CO;2-H

      The first attempt at using metal carbonyls as precursors for mesostructured materials, reported here, suggests that this new approach to metal carbonyl, metal carbide, and purely metallic mesostructured materials holds promise. The precipitation of platinum carbonyl anions of the type [Pr3(CO6)n]2− (n = 3 to 5) with cetyltrimethylammonium chloride is shown to lead to layered platinum carbonyl phases, which lose CO under thermal conditions to form layered platinum-based phases. Mesostructured metals are important in nanoscale electronic applications and in catalytic processes involving large molecules.

    5. Ultrathin Diblock Copolymer/Titanium Laminates—A Tool for Nanolithography (pages 849–852)

      Joachim P. Spatz, Peter Eibeck, Stefan Mößmer, Martin Möller, Thomas Herzog and Paul Ziemann

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199808)10:11<849::AID-ADMA849>3.0.CO;2-5

      A self-assembled diblock copolymer mask teamed with conventional ion etching is one approach to nanometer patterning of surfaces. An ultrathin film of polystyrene-block-poly(2-vinylpyridine) on mica is shown to yield isolated, regularly arranged clusters of polystyrene surrounded by a thin layer of poly(2-vinylpyridine)—see Figure. Subsequent selective deposition of a metal film followed by etching results in surface patterning.

    6. Novel Polymer Dyes for Nonlinear Optical Applications Using Ionic Self-Assembled Monolayer Technology (pages 853–855)

      Kristie M. Lenahan, You-Xiong Wang, Yanjing Liu, Richard O. Claus, James R. Heflin, Daniela Marciu and Charles Figura

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199808)10:11<853::AID-ADMA853>3.0.CO;2-P

      The advantages of the ionic self-assembled monolayer (ISAM) technique are demonstrated for the fabrication of non-centrosymmetric thin films of new nonlinear optical (NLO) polymers. Results are presented, e.g., from UV-vis spectroscopy, fluorescence spectroscopy, and second-harmonic generation experiments, that confirm the second-order NLO behavior of these polydye materials. One of the materials is shown to have not only a stronger ω(2) response—which should not decay over time—but also a higher degree of ordering than commercially available polymers.

    7. Holographic Data Storage in Amorphous Polymers (pages 855–859)

      Stephan J. Zilker, Thomas Bieringer, Dietrich Haarer, Richard S. Stein, Jan W. van Egmond and Sergey G. Kostromine

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199808)10:11<855::AID-ADMA855>3.0.CO;2-H

      New polymers for optical recording materials are presented. The origin of the light-induced refractive index modulation, the thermal gain effect, and the aims of future developments are discussed. The Figure shows the reconstruction of an X-ray picture of a tooth, which had previously been written into the sample by exposure to an s-polarized argon ion beam. See also the cover.

    8. Fluorine Tin Oxide as an Alternative to Indium Tin Oxide in Polymer LEDs (pages 859–863)

      Annica Andersson, Nicklas Johansson, Per Bröms, Nu Yu, Donald Lupo and William R. Salaneck

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199808)10:11<859::AID-ADMA859>3.0.CO;2-1

      Fluorine-doped tin oxide (FTO) electrodes have been investigated for use instead of indium-doped tin oxide (ITO) as the holeinjecting electrode in polymer light-emitting diodes (LEDs). The initial results presented here lead to the conclusion that the electrode–polymer interface is much more complex than a simple energy level diagram might imply. Single-layer devices that differ only in the material of the electrode (FTO or ITO) are compared, as are the effects of different methods of cleaning the electrode material. FTO is shown to offer several advantages over ITO—including its cost.

    9. Ambient-Temperature Liquid-Crystalline Bismethacrylates Based on Cholesterol: Cholesteric and Smectic Thermosets (pages 864–868)

      Dirk Hölter, Holger Frey, Rolf Mülhaupt and Joachim E. Klee

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199808)10:11<864::AID-ADMA864>3.0.CO;2-H

      Liquid-crystalline (LC) thermosets make it possible to fix LC order permanently and to produce materials with anisotropic properties of interest in electronics and optics. Branched LC bismethacrylates based on cholesterol as the mesogenic unit are described (see Figure) that exhibit stable mesophases at ambient temperature. A convenient pathway to photocrosslinkable LC monomers from a commercial bismethacrylate is introduced.

    10. Microlasers and Micro-LEDs from Disubstituted Polyacetylene (pages 869–872)

      Sergey V. Frolov, Akihiko Fujii, Douglas Chinn, Masaharu Hirohata, Rahmat Hidayat, Masahiro Taraguchi, Toshio Masuda, Katsumi Yoshino and Z. Valy Vardeny

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199808)10:11<869::AID-ADMA869>3.0.CO;2-Y

      Photopumped pulsed lasing in the green spectral range is reported for cylindrical microcavities in which the active layers are films of disubstituted polyacetylene derivatives. The various cavity-dependent laser modes observed in both micro-rings coated around thin optical fibers and microdisks deposited on flat quartz substrates are described. In addition the feasibility of fabricating high Q cylindrical light-emitting diodes (LEDs) from flat polymer microdisks is demonstrated—an important step towards the realization of electrically pumped, green-emitting, plastic laser diodes using cylindrical microcavities.

    11. Lyotropic Liquid-Crystalline Behavior in Disc-Shaped Compounds Incorporating the 3,3′-Di(acylamino)-2,2′-bipyridine Unit (pages 873–876)

      Anja R. A. Palmans, Jozef A. J. M. Vekemans, Rifat A. Hikmet, Hartmut Fischer and E. W. Meijer

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199808)10:11<873::AID-ADMA873>3.0.CO;2-H

      An extended-core liquid crystal (LC) based on the 3,3′-di(acylamino)-2,2′-bipyridine unit is investigated with respect to its behavior in alkane solvents. It is demonstrated that the lyotropic mesomorphism observed in dodecane can be tuned by varying the concentration of the sample, and the columns can be switched in an electric field. The Figure shows the structure of the columnar nematic phase present in dodecane containing 15.7 wt.-% LC.

    12. High Density Rechargeable Lithium-Ion Batteries Self-Assembled from Graphite Oxide Nanoplatelets and Polyelectrolytes (pages 877–881)

      Thierry Cassagneau and Janos H. Fendler

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199808)10:11<877::AID-ADMA877>3.0.CO;2-1

      The construction of a high-capacity intercalating cathode via an entirely new approach is reported—the self-assembly of nanometer-thick polyelectrolytes and graphite/graphite oxide nanoplatelets on a conducting substrate. The advantages of this approach as well as the charging and discharging behavior of a high-density (1232 mAhg–1 of graphitic carbon) rechargeable lithium-ion battery based on this cathode are described. This electrochemical cell holds commercial promise as it may be readily scaled up to an economically viable battery.

    13. The Role of Defects in the Formation of Mesoporous Silica Fibers, Films, and Curved Shapes (pages 883–887)

      Hong Yang, Geoffrey A. Ozin and Charles T. Kresge

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199808)10:11<883::AID-ADMA883>3.0.CO;2-D

      The growth of particular forms of mesoporous silica can be initiated and directed by topological defects in the silicate liquid crystal seed. The role of these defects in the formation of a collection of synthetic hexagonal mesoporous silica morphologies is discussed. The Figure is an image of a flat toroid, one of the morphologies that might arise from a single defect.

    14. Giant Vesicles: Micromanipulation of Membrane Bilayers (pages 888–890)

      Fredric M. Menger and Jason S. Keiper

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199808)10:11<888::AID-ADMA888>3.0.CO;2-U

      Micromanipulation of giant vesicles—spherical bilayer assemblies with a size and curvature comparable to living cells—is possible using common cytological techniques. This allows discrete colloidal particles to be controlled and experimented on, simplifying the investigation of mechanical, thermal, and (bio)chemical perturbations. Some of the approaches to giant vesicle micromanipulation as well as several recent developments are highlighted, including optical trapping and the possibility of adding or removing components to or from a vesicle's interior by direct insertion of a glass micropipet.