Advanced Materials

Cover image for Advanced Materials

November, 1998

Volume 10, Issue 16

Pages 1297–1394

    1. From Molecules to Materials: Current Trends and Future Directions (pages 1297–1336)

      Paul Alivisatos, Paul F. Barbara, A. Welford Castleman, Jack Chang, David A. Dixon, Michael L. Klein, George L. McLendon, Joel S. Miller, Mark A. Ratner, Peter J. Rossky, Samuel I. Stupp and Mark E. Thompson

      Version of Record online: 8 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199811)10:16<1297::AID-ADMA1297>3.0.CO;2-7

      The development, characterization, and exploitation of novel materials based on the assembly of molecular components is an exceptionally active and rapidly expanding field. This review presents examples of the critical role of cross-disciplinary research in achieving designed molecule-based materials. The Figure shows a near-field scanning optical microscopy image of a mesostructure of an organic thin-film sample.

    2. Trifunctional Light-Emitting Molecules Based on Rhenium and Ruthenium Bipyridine Complexes (pages 1337–1340)

      Xiong Gong, Po King Ng and Wai Kin Chan

      Version of Record online: 8 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199811)10:16<1337::AID-ADMA1337>3.0.CO;2-D

      The synthesis and light-emitting properties of two novel, trifunctional, light-emitting molecules based on rhenium(I) and ruthenium(II) bipyridine complexes are described. The hole-transporting, electron-transporting, and light-emitting functional groups are incorporated into one molecule. The authors report that their approach provides flexibility since the optoelectronic properties can be modified by varying the ligand and/or the metal component. For example, a multicolor display is claimed to be possible by preparing mixed metal complexes.

    3. Soluble Phenyl-Substituted PPVs—New Materials for Highly Efficient Polymer LEDs (pages 1340–1343)

      Hubert Spreitzer, Heinrich Becker, Edgar Kluge, Willi Kreuder, Hermann Schenk, Rob Demandt and Herman Schoo

      Version of Record online: 8 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199811)10:16<1340::AID-ADMA1340>3.0.CO;2-G

      A new class of soluble electroluminescent poly(p-phenylenevinylene)s (PPVs) is introduced here. Alkoxy-substituted 2-phenyl PPVs (see Figure for a schematic representation) are found to exhibit very good solubility in the conjugated state, good film-forming properties, high molecular weights, and excellent electroluminescence performance. With a simple device setup the researchers achieved very high efficiencies.

    4. Investigation of Exciton Coupling in Oligothiophenes by Circular Dichroism Spectroscopy (pages 1343–1348)

      Bea M. W. Langeveld-Voss, David Beljonne, Zhigang Shuai, René A. J. Janssen, Stefan C. J. Meskers, E. W. Meijer and Jean-Luc Brédas

      Version of Record online: 8 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199811)10:16<1343::AID-ADMA1343>3.0.CO;2-Z

      The solid-state photophysical properties of semiconducting polymers result from the interplay between the intrinsic features of the polymer chains and interchain interactions. Exciton coupling, which in principle can be estimated from circular dichroism (CD) spectra, is one of the major interchain interactions affecting the optical properties of semiconducting polymers. Here the authors present a combined experimental and theoretical investigation of the chiroptical properties of oligothiophenes. The results confirm that the CD spectrum provides an independent estimate of the exciton coupling.

    5. A Light-Driven Switch Based on Photochromic Dihydroindolizines (pages 1348–1351)

      Christian Weber, Felix Rustemeyer and Heinz Dürr

      Version of Record online: 8 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199811)10:16<1348::AID-ADMA1348>3.0.CO;2-5

      A molecular switching device based on a photochromic dihydroindolizine (DHI) with non-destructive read-out capacity (see Figure for a schematic representation of the erasable dual-mode optical switch) is presented. Two different DHIs based on a pyridazine and a chinoline heterocycle have been investigated and the results show that these systems can be of potential use for non-destructive readout optical memory.

    6. Inherently Electrically Conductive Fibers Wet Spun from a Sulfonic Acid–Doped Polyaniline Solution (pages 1351–1353)

      Stephen J. Pomfret, Phillip N. Adams, Nigel P. Comfort and Andrew P. Monkman

      Version of Record online: 8 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199811)10:16<1351::AID-ADMA1351>3.0.CO;2-8

      Wet spinning of fibers from a solution of polyaniline doped with 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPSA) is reported. The fibers spun into selected coagulation solvents are inherently electrically conductive and can be cold drawn to extensions of >500%with a concomitant rise in electrical conductivity of ∼1500%. The fibers appear to be void free and, when drawn, the strain-hardened fibers show final breaking strains of the order of 50 MPa. These fibers are stable in air and could be produced cheaply on an industrial scale.

    7. Development of Chromogenic Copolymers for Optical Detection of Amines (pages 1353–1357)

      Gerhard J. Mohr, Nicola Tirelli, Christian Lohse and Ursula E. Spichiger-Keller

      Version of Record online: 8 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199811)10:16<1353::AID-ADMA1353>3.0.CO;2-X

      New sensor membranes for detecting aliphatic amines have been developed by copolymerization of a polymerizable dye (see Figure) with various copolymers. Compared to existing optical sensor membranes they are reported to have a longer shelf life and are operationally more stable. The analyte recognition and color change are based on a reversible chemical reaction rather than a physical complexation.

    8. Evidence of Aggregation-Induced Copper Immobilization During Polyimide Metallization (pages 1357–1360)

      Michael Kiene, Thomas Strunskus, Ralf Peter and Franz Faupel

      Version of Record online: 8 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199811)10:16<1357::AID-ADMA1357>3.0.CO;2-9

      Research on metal diffusion into polymers and metal–polymer interfaces is mainly stimulated by applications of polyimide in microelectronics packaging and at the chip level. Since copper will increasingly replace aluminum in such applications as a result of miniaturization, the interfacial behavior of copper is of great importance. The authors use combined X-ray photoelectron spectroscopy and transmission electron microscopy to show that copper does not diffuse into polyimide from a continuous film. Strong diffusion of Cu is shown to require extremely low deposition rates, far below those of practical importance.

    9. A Novel Bis(tetrathiafulvalene) Cyclophane: Synthesis, Electrochemical Properties, and X-ray Crystal Structures of the Neutral and Radical Cation Species (pages 1360–1363)

      Andrei S. Batsanov, Derek E. John, Martin R. Bryce and Judith A. K. Howard

      Version of Record online: 8 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199811)10:16<1360::AID-ADMA1360>3.0.CO;2-C

      Dimeric tetrathiafulvalene (TTF) derivatives have been studied as π-electron donor components of organic conductors. The authors report the synthesis of a novel bis(TTF) cyclophane (see Figure), which possesses a rare “edge-to-face” double linkage of two TTF units, joined by two bridges. The solution electrochemistry of this molecule is described, as are the X-ray structures of the neutral molecule and two cation radical salts.

    10. High Resolution X-ray Diffraction Study of a Tubular Liquid Crystal (pages 1363–1366)

      Oksana Y. Mindyuk, MacKenzie R. Stetzer, Paul A. Heiney, James C. Nelson and Jeffrey S. Moore

      Version of Record online: 8 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199811)10:16<1363::AID-ADMA1363>3.0.CO;2-V

      Complexes of discotic liquid crystals would ideally possess the conductive properties of semiconductors and metals as well as the highly anisotropic mechanical, optical and structural properties of liquid crystals. High-resolution X-ray diffraction is used by the authors to study the structure of a liquid-crystalline conjugated phenylacetylene macrocycle doped with a silver salt. The results show that the silver ions are intercalated within the tubes, providing the first step towards the development of novel anisotropic liquid-crystalline ionic conductors.

    11. A Poly(bis[2]catenane) Containing a Combination of Covalent, Mechanical, and Coordinative Bonds (pages 1366–1369)

      Christoph Hamers, Oldrich Kocian, Françisco M. Raymo and J. Fraser Stoddart

      Version of Record online: 8 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199811)10:16<1366::AID-ADMA1366>3.0.CO;2-D

      The donor/acceptor template-directed synthesis of a bis[2]catenane incorporating 2,2′-bipyridine ligands within both [2]catenane subunits and the self- assembly of a poly(bis[2]catenane) (see Figure for a schematic representation) is reported here. This molecule is a rare example of a mechanically interlocked coordination polymer—a class of intriguing supramolecular polymers with potentially unusual properties.

    12. Novel Ribbon-Shaped α-Al2O3 Fibers (pages 1370–1373)

      Víctor Valcárcel, Antonio Pérez, Marek Cyrklaff and Francisco Guitián

      Version of Record online: 8 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199811)10:16<1370::AID-ADMA1370>3.0.CO;2-A

      The use of Al2O3 polycrystalline fibers and whiskers as strengtheners in high-temperature composites is of great interest owing to their high elastic modulus and their thermal and chemical stability. The authors describe in this communication a novel type of crystalline α-Al2O3 fiber. These new fibers—termed ribbons by the authors—have a high specific surface area, which, together with their optical properties and low cost, makes them suitable for use as protective films in composites and as crystalline surfaces for other α-Al2O3 fiber production methods.

    13. Organization of Hydrophilic Nanoparticles on a Hydrogel Surface and Their Gel-Assisted Transfer to Solid Substrates (pages 1373–1376)

      Nobuo Kimizuka, Shigenori Fujikawa and Toyoki Kunitake

      Version of Record online: 8 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199811)10:16<1373::AID-ADMA1373>3.0.CO;2-T

      Two-dimensional organization of water-soluble nanoparticles, by using a hydrogel (agarose gel) surface as a substrate, is described here. The nanoparticles can be subsequently transferred onto various solid surfaces, a process promoted by the agarose acting as a “molecular glue”. The Figure shows silica nanoparticles transferred to a highly oriented pyrolytic graphite surface.

    14. New Approaches to Pore Size Engineering of Mesoporous Silicates (pages 1376–1379)

      Abdelhamid Sayari, Michal Kruk, Mietek Jaroniec and Igor L. Moudrakovski

      Version of Record online: 8 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199811)10:16<1376::AID-ADMA1376>3.0.CO;2-B

      Pore size engineering of silicates has always been a critical issue in the field of mesoporous materials design. A new method for obtaining silicates with pore sizes up to 11 nm and narrow pore size distributions is described by the authors. Treating non-calcined MCM-41 silicate in aqueous emulsions of long-chain alkylamines, they generated these materials with large pores and exceptionally high pore volumes. Direct synthesis in the presence of long-chain alkylamines affords materials with up to 8 nm pores. These simple techniques are thought to be applicable to other molecular sieves.

    15. Continuous Mesoporous Silica Films with Highly Ordered Large Pore Structures (pages 1380–1385)

      Dongyuan Zhao, Peidong Yang, Nick Melosh, Jianglin Feng, Bradley F. Chmelka and Galen D. Stucky

      Version of Record online: 8 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199811)10:16<1380::AID-ADMA1380>3.0.CO;2-8

      The formation of continuous mesoporous silica films with large periodic cage and pore structures is reported here. The authors use low-cost commercially available triblock copolymers and poly(ethylene oxide) non-ionic surfactants as the structure-directing agents in conjunction with dip-coat processing. In the Figure a transmission electron microscope image of a calcined hexagonal mesoporous silica film is shown.

    16. Polymer Particles by Templating of Vesicles (pages 1387–1390)

      Jutta Hotz and Wolfgang Meier

      Version of Record online: 8 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199811)10:16<1387::AID-ADMA1387>3.0.CO;2-3

      Template-directed synthesis is an elegant approach to defined nanostructured materials. Vesicles or liposomes have already been used in the synthesis of small inorganic particles, but their use as a template for polymer synthesis is rare. Despite this, direct templating of vesicles offers interesting new possibilities for the formation of defined nanostructured polymers. While the polymer morphology is determined by the size and shape of the templates, the polymer framework can be modified by conventional chemical reactions. The authors envisage applications in separation processes or drug delivery.

    17. Supramolecular Templates as Porogenes (pages 1391–1394)

      Uwe Beginn

      Version of Record online: 8 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199811)10:16<1391::AID-ADMA1391>3.0.CO;2-0

      Well-defined mesoporous materials can be synthesized using template strategies, which resemble macroscopic metal casting processes. Templates that preform the shapes of the pores, like casting-cores, are introduced into a liquid system and subsequently embedded by hardening of the solvent. In the Figure the formation of a mesoporous solid via complexation of a linear macromolecule is schematically represented.