Advanced Materials

Cover image for Advanced Materials

March, 1998

Volume 10, Issue 4

Pages 279–353

    1. Heteroatom-Based Dendrimers (pages 279–293)

      Holger Frey, Christian Lach and Klaus Lorenz

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199803)10:4<279::AID-ADMA279>3.0.CO;2-F

      Heteroatom-based dendrimers, i.e., dendrimers whose connectivity is based on atoms other than carbon, are reviewed, with emphasis being placed on recent developments and how these materials can be exploited for the rational design of ordered molecular materials. The Figure shows a palladium-metallized organophosphine dendrimer, phosphorus-based dendrimers being one of the three main groups of dendrimers based on heteroatoms.

    2. Metallodendrimers: Structural Diversity and Functional Behavior (pages 295–309)

      Christopher Gorman

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199803)10:4<295::AID-ADMA295>3.0.CO;2-N

      This review of metallodendrimers has two main goals: first, to illustrate the various structure types of metallodendrimers, demonstrating their substantial structural diversity, and second, to highlight their applications, either potential or already coming into existence. Applications include metallodendrimers as nanoparticle equivalents, for sensing and imaging, for catalysis, and as molecular antennas or for producing controlled microenvironments. Their electrochemical behavior is also considered. The difficulty of representing the three-dimensional structure of metallodendrimers is touched upon.

    3. Picking Needles from Nano-Haystacks (pages 311–313)

      Seamus Curran, David L. Carroll, Pulickel M. Ajayan, Philipp Redlich, Siegmar Roth, Manfred Rühle and Werner Blau

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199803)10:4<311::AID-ADMA311>3.0.CO;2-U

      The selection, manipulation, and deformation of individual nanotubes are demonstrated using the scanning tunneling microscope (STM). For example, the Figure shows two tubes in the foreground that have been removed from the loose bundle of nanotubes behind. The technique explained here will make taking measurements on individual nanotubes less like looking for a needle (to measure) in a haystack.

    4. A Non-surfactant Templating Route to Mesoporous Silica Materials (pages 313–316)

      Yen Wei, Danliang Jin, Tianzhong Ding, Wei-Heng Shih, Xinghua Liu, Stephen Z. D. Cheng and Qiang Fu

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199803)10:4<313::AID-ADMA313>3.0.CO;2-M

      The templated synthesis of mesoporous materials using surfactant templates has been known since 1992. The discovery reported here, that non-surfactant organic molecules, e.g., optically active organic compounds such as D-glucose, also act as templates for the formation of mesoporous silica materials with large surface areas and pore volumes and narrow pore size distribution, opens new opportunities for the preparation of mesostructural materials because of the vast diversity of organic compounds that may function as templates.

    5. Single-Molecule Force Spectroscopy on Xanthan by AFM (pages 316–319)

      Hongbin Li, Matthias Rief, Filipp Oesterhelt and Hermann E. Gaub

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199803)10:4<316::AID-ADMA316>3.0.CO;2-A

      Single-molecule force spectroscopy, a new technique that is useful for exploring the mechanical properties of single polymer coils and also for examining polymers with specific secondary structures, is described. The Figure shows the principle of the experiment. A thin layer of the sample is placed on a piezo crystal and stretched using the tip of the atomic force microscope, allowing force–extension curves to be derived.

    6. The Vibrational Signature of the Aluminum/Polythiophene Interface (pages 319–324)

      Vincent Parente, Geoffrey Pourtois, Roberto Lazzaroni, Jean-Luc Brédas, Gianpiero Ruani, Mauro Murgia and Roberto Zamboni

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199803)10:4<319::AID-ADMA319>3.0.CO;2-Z

      An understanding and control of metal–polymer interfaces is important for the development of conjugated polymer–based light-emitting diodes. For example, do interactions at the interface modify the geometric structure and electronic properties of the conjugated system? This question is addressed here by a combined theoretical and experimental approach that has allowed the vibrational properties—which are intimately related to molecular structure and bonding—of interfaces between aluminum and oligothiophenes to be determined.

    7. Specific Recognition of Nucleobase-Functionalized Polythiophenes (pages 324–330)

      Peter Bäuerle and Andreas Emge

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199803)10:4<324::AID-ADMA324>3.0.CO;2-E

      The first nucleobase-functionalized polythiophenes, e.g., the uracil-substituted polythiophene shown in the Figure, produced by electrochemical oxidation of bithiophenes covalently linked to the nucleobases uracil and adenine, are reported. Their synthesis, characterization, and polymerization are detailed and the influence of molecular recognition processes on their electronic properties are described.

    8. A New Family of Sulfur Dioxide–Containing TTF Derivatives (pages 330–334)

      Josep Llacay, Ignasi Mata, Elies Molins, Jaume Veciana and Concepció Rovira

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199803)10:4<330::AID-ADMA330>3.0.CO;2-Q

      One sulfone group substituted into the tetrathiafulvalene (TTF) core is reported to influence the crystal packing of this family of compounds by permitting hydrogen bonds to be established. In addition, the incorporated 3-sulfolene moiety is shown to open up a new direction in TTF chemistry by allowing Diels–Alder reactions and related cycloadditions. The synthesis of this family of compounds is described along with the results of a crystal structure investigation. It is shown that the introduction of the 3 sulfolene moiety does not affect the properties of the π-electron system.

    9. Syntheses, Charge Distribution, and Molecular Second-Order Nonlinear Optical Properties of Push–Pull Bisdithiolene Nickel Complexes (pages 334–338)

      Chin-Ti Chen, Sish-Yuan Liao, Kuan-Jiuh Lin and Long-Li Lai

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199803)10:4<334::AID-ADMA334>3.0.CO;2-A

      The second-order nonlinear optical (NLO) properties of some bisdithiophene d8 metal complexes, for example, the donor–acceptor unsymmetrically substituted bisdithiophene nickel(II) complex shown in the Figure, are reported for the first time. The synthesis and characterization of the complexes are described and the relationship between their charge distributions and NLO properties is discussed.

    10. Nonlinear Optical Properties of Polyelectrolyte Thin Films Containing Gold Nanoparticles Investigated by Wavelength Dispersive Femtosecond Degenerate Four Wave Mixing (DFWM) (pages 338–341)

      Wolfgang Schrof, Stanislav Rozouvan, Edward Van Keuren, Dieter Horn, Johannes Schmitt and Gero Decher

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199803)10:4<338::AID-ADMA338>3.0.CO;2-V

      The nonlinear optical (NLO) properties of gold nanoparticles embedded in polyelectrolyte multilayer thin films, in particular the dispersion of the third-order nonlinearity and its relaxation around the plasmon band, have been investigated by femtosecond wavelength dispersive degenerate four wave mixing. The experimental results are discussed in terms of a simple model for the third-order optical nonlinearity of nanoparticle systems. The results demonstrate that not only is the color of metallic nanoparticles dominated by surface plasmon optical resonance but surface plasmons govern NLO phenomena as well.

    11. Opalescent Cholesteric Networks from Chiral Polyisocyanates in Polystyrene (pages 341–345)

      Georg Maxein, Harald Keller, Bruce M. Novak and Rudolf Zentel

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199803)10:4<341::AID-ADMA341>3.0.CO;2-I

      The cholesteric polymer films described here, i.e., the “locked in” chiral nematic phase of polymer liquid crystals, have several advantages as materials for optical applications. The Figure shows schematically a cholesteric network based on a chiral isocyanate terpolymer in styrene in which the cholesteric liquid-crystalline structure is “locked in” by photopolymerization.

    12. Redox-Active Polyelectrolyte Multilayers (pages 347–349)

      Joseph B. Schlenoff, Delphine Laurent, Hiep Ly and Jason Stepp

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199803)10:4<347::AID-ADMA347>3.0.CO;2-V

      Uniform multilayer films of polyelectrolytes (charged polymers) that incorporate redox-active polyelectrolytes are demonstrated to be formed by a simple electrostatic layer-by-layer approach. On conducting substrates, the redox sites within these films are addressable by electrochemical methods. This is verified by considering two examples—the electrochromism and electrocatalysis of polyviologen multilayers—to check that the physical properties of these films are modulated by electrochemistry.

    13. Surprising Superstructures: Rings (pages 351–353)

      Tobias Vossmeyer, Sung-Wook Chung, William M. Gelbart and James R. Heath

      Version of Record online: 26 JAN 1999 | DOI: 10.1002/(SICI)1521-4095(199803)10:4<351::AID-ADMA351>3.0.CO;2-E

      The symmetries of superstructures are often determined by the shape of the subunits, e.g., spheres, disks, or rods. Ring superstructures would not be predicted for any of these subunit shapes, but have in fact recently been found, as can be seen from the Figure, a scanning electron micrograph of carbon nanotube rings. The ring superstructures observed for three diverse materials are discussed and the systems compared and contrasted.