Advanced Materials

Cover image for Advanced Materials

October, 2000

Volume 12, Issue 20

Pages 1481–1549

    1. Surface Modification of Fluoropolymers via Molecular Design (pages 1481–1494)

      E. T. Kang and Y. Zhang

      Article first published online: 23 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:20<1481::AID-ADMA1481>3.0.CO;2-Z

      Fluoropolymer surfaces with new and specific functionalities, such as metal-free conductivity, biocompatability, and bondability to metals, can be obtained through the intelligent choice of functional monomers for graft copolymerization on pre-activated fluoropolymer surfaces, as highlighted in this review. The Figure shows a gold/fluoropolymer laminate held together by crosslinked glycidyl methacrylate polymer grafted on both surfaces.

    2. Change of Liquid-Crystal Domains by Vibrational Excitation for a Columnar Mesophase (pages 1495–1499)

      H. Monobe, K. Awazu and Y. Shimizu

      Article first published online: 23 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:20<1495::AID-ADMA1495>3.0.CO;2-9

      Molecular alignment of liquid crystals using infrared light is presented as a viable alternative to UV-vis irradiation. In this technique, a free electron laser (FEL) is used to vibrationally excite the columnar mesophase of the triphenylene-based discotic liquid crystal HHOT. Upon FEL irradiation the microscopic texture of the HHOT film changes (see Figure), associated with a change in the alignment of the columns.

    3. Photonic Crystal Films with High Refractive Index Contrast (pages 1499–1503)

      M. Müller, R. Zentel, T. Maka, S. G. Romanov and C. M. Sotomayor Torres

      Article first published online: 23 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:20<1499::AID-ADMA1499>3.0.CO;2-M

      Large-area inverted photonic crystals of SnS2 are prepared here by infilling poly(methylmethacrylate) (PMMA) opaline thin films with SnS2 by chemical vapor deposition. Dissolution of the polymer beads leaves a large inverted replica with good optical properties (see Figure), owing to the high bulk refractive index and wide electronic gap of the material.

    4. The Interplay of Colloidal Organization and Oxo-Cluster Chemistry: Polyoxometalate–Silica Hybrids—Materials with a Nanochemical Function (pages 1503–1507)

      S. Polarz, B. Smarsly, C. Göltner and M. Antonietti

      Article first published online: 23 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:20<1503::AID-ADMA1503>3.0.CO;2-X

      Polyoxometalates of colloidal size have been immobilized in a silica-matrix via sol-gel synthesis. The resulting (porous) materials exhibit the unique properties of both the polyoxometalates (POMs) and of the host silica. The pocket molded into the silica by the POM-cluster acts as a special nano-dimensional “reaction vessel”, where the POMs can undergo chemical transformations without leaching of the molybdato units.

    5. Nanoscale Assembly of Metal Clusters in Block Copolymer Films with Vapor of a Metal–Acetylacetonato Complex Using a Dry Process (pages 1507–1511)

      S. Horiuchi, M. I. Sarwar and Y. Nakao

      Article first published online: 23 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:20<1507::AID-ADMA1507>3.0.CO;2-9

      A dry route to nanosized palladium clusters, involving the vaporization of Pd(acac)2 in the presence of block copolymer films, is introduced here. It is demonstrated that the Pd clusters grow selectively in one of the phases of the block copolymer, aligning themselves along the polymer's lamellar microdomains (see Figure). Clusters of small size and narrow distribution are obtained.

    6. Colloidal Ellipsoids with Continuously Variable Shape (pages 1511–1514)

      E. Snoeks, A. van Blaaderen, T. van Dillen, C. M. van Kats, M. L. Brongersma and A. Polman

      Article first published online: 23 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:20<1511::AID-ADMA1511>3.0.CO;2-6

      Oblate and prolate ellipsoidal inorganic colloids can be synthesized by combining colloidal chemistry and ion irradiation techniques, as reported here. It is found that dramatic anisotropic plastic deformation of monodisperse silica and zinc sulfide microspheres occurs under 4 MeV Xe ion irradiation (see Figure). Possible application in the assembly of liquid crystals is demonstrated.

    7. Ultraflat Nanosphere Lithography: A New Method to Fabricate Flat Nanostructures (pages 1515–1519)

      W. Frey, C. K. Woods and A. Chilkoti

      Article first published online: 23 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:20<1515::AID-ADMA1515>3.0.CO;2-J

      Ultraflat nanopatterned surfaces can be created by combining the techniques of nanosphere lithography and ultraflat template stripping, as highlighted here. In this new method—ultraflat nanosphere lithography (UNSL)—nanostructures of one material are embedded in a matrix of a second material (see Figure). The feasibility of UNSL is demonstrated for several pairs of materials.

    8. Au@SnO2 Core–Shell Nanocapacitors (pages 1519–1522)

      G. Oldfield, T. Ung and P. Mulvaney

      Article first published online: 23 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:20<1519::AID-ADMA1519>3.0.CO;2-W

      The reproducible synthesis of metal–semiconductor core–shell nanoparticles consisting of 15 nm gold colloids homogeneously coated with a 10 nm layer of SnO2 is reported (see Figure). The surface plasmon band is drastically red-shifted from 521 to 542 nm. These materials display a high electrical capacitance and slow discharge rates in solution, indicating potential applications as electro-optical switches, supercapacitors, and redox catalysts.

    9. A Novel Peanut-like Nanostructure of II–VI Semiconductor CdS and ZnS (pages 1523–1526)

      Y. Xie, J. Huang, B. Li, Y. Liu and Y. Qian

      Article first published online: 23 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:20<1523::AID-ADMA1523>3.0.CO;2-T

      Metal sulfide cores self-encapsulated in shells of the same material are formed via the in-situ source–template interface reaction route described by these authors. In this method, reaction occurs at the static organic/aqueous interface to produce peanut-shaped nanostructures of either CdS or ZnS (see Figure). A mechanism for the formation of these novel structures is proposed.

    10. Surfactant-Induced Mesoscopic Assemblies of Inorganic Molecular Chains (pages 1526–1528)

      B. Messer, J. H. Song, M. Huang, Y. Wu, F. Kim and P. Yang

      Article first published online: 23 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:20<1526::AID-ADMA1526>3.0.CO;2-B

      A disassembly–reassemblyapproach is used here in the self-organization of [Mo3Se3] chains—possible molecular wires. Either lamellar or hexagonal mesostructures (see Figure) are formed in the presence of oppositely charged surfactants and the spacing between these inorganic chains can be varied (20–40 Å) by using surfactants with different alkane lengths.

    11. Structural Control of Surfactant-Templated Hexagonal, Cubic, and Lamellar Mesoporous Silicate Thin Films Prepared by Spin-Casting (pages 1529–1533)

      I. Honma, H. S. Zhou, D. Kundu and A. Endo

      Article first published online: 23 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:20<1529::AID-ADMA1529>3.0.CO;2-U

      Large-area mesoporous silicate thin films are reported to be formed on solid silica substrates by the simple technique of spin-coating. The mesophase of the films can be controlled to be one-dimensional hexagonal, cubic, or lamellar by adjusting the casting solution composition, i.e., mainly the ratio of surfactant to tetraethyl orthosilicate (TEOS). The X-ray diffraction results leading to the assignment of the mesophase types are presented and reasons for the change of phase with solution composition discussed. The films are expected to have applications in catalysis, molecular separation, and sensors.

    12. Photorefractivity in Ferroelectric Liquid Crystal Composites Containing Electron Donor and Acceptor Molecules (pages 1533–1536)

      G. P. Wiederrecht, B. A. Yoon and M. R. Wasielewski

      Article first published online: 23 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:20<1533::AID-ADMA1533>3.0.CO;2-R

      The first observation of photorefractivity in ferroelectric liquid crystals (FLCs) is reported here. Dopant chromophores chosen to optimize production of mobile ions and careful control of the wavevector and light polarization are believed to play a decisive role in the observed behavior. The Figure is a schematic illustration of the experimental geometry used.

    13. Flexible Smart Window via Surface Graft Copolymerization of Viologen on Polyethylene (pages 1536–1539)

      J. T. Sampanthar, K. G. Neoh, S. W. Ng, E. T. Kang and K. L. Tan

      Article first published online: 23 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:20<1536::AID-ADMA1536>3.0.CO;2-9

      Transparent “smart” windows comprising a thin layer of viologen on low-density polyethylene are fabricated here via graft polymerization. The transmittance of this system is reduced when exposed to light as the viologen dication is converted to monocation (see Figure). A rapid and reproducible response is observed.

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      Electron Transport in Fluorinated Copper-Phthalocyanine (pages 1539–1542)

      J. H. Schön, C. Kloc, Z. Bao and B. Batlogg

      Article first published online: 23 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:20<1539::AID-ADMA1539>3.0.CO;2-S

      Air-stable n-type organic semiconductorswith high mobilities have been actively pursued since organic transistors have proven their importance in the development of low-cost electronics. A promising candidate, fluorinated copper-phthalocyanine, is investigated here. Electron transport properties are presented here for polycrystalline thin films and for single crystals of this compound, and it is reported that stable device performance in air can be achieved. The intrinsic transport mechanism is found to be band-like charge transport. Effects of trapping and grain boundaries are also discussed.

    15. Polymer/Calcium Carbonate Layered Thin-Film Composites (pages 1543–1546)

      T. Kato

      Article first published online: 23 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:20<1543::AID-ADMA1543>3.0.CO;2-P

      Formation of the nacre of a shellis mimicked here to synthesize layered polymer/calcium carbonate composites such as that shown in the Figure. The combination of insoluble chitin or chitosan solid matrices with soluble acidic macromolecules such as poly(acrylic acid) is used to induce thin-film crystallization of CaCO3 on the solid matrices. The polymorph formed can also be controlled employing this method.

    16. Electrochemical Growth of Nanosized Conducting Polymer Wires on Gold Using Molecular Templates (pages 1547–1549)

      S.-J. Choi and S.-M. Park

      Article first published online: 23 OCT 2000 | DOI: 10.1002/1521-4095(200010)12:20<1547::AID-ADMA1547>3.0.CO;2-1

      Conducting polymer nanowires and nanorings(see Figure) can be synthesized using the strategy described here—electrochemical growth on gold electrodes modified with self-assembled monolayers (SAMs) of well-separated thiolated cyclodextrins in an alkanethiol “forest”. Thiolated aniline monomer is anchored to the surface within the cyclodextrin cavity and forms an initiation point for polymer wire growth.

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