Advanced Materials

Cover image for Advanced Materials

March 1994

Volume 6, Issue 3

Pages fmi–fmi, 187–254

  1. Masthead

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

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060301

  2. Essay

    1. Top of page
    2. Masthead
    3. Essay
    4. Reviews
    5. Communications
    6. Materaials Forum
    7. Research News
    8. Book Reviews
    1. Materials R&D at los alamos national laboratory (pages 187–189)

      Dr. Paul S. Follansbee

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060302

      The materials programs at Los Alamos National Laboratory (LANL) have broadend tremendously since the laboratory was originally founded to support the Mahattan Project, which led to the development of the atomic bomb. Alongside the primary national security mission of the laboratory, collaborations with industry that make use of the special expertise gathered at LANL are growing in importance. Some of the unique facilities available at LANL are described and several projects are highlighted, providing a good idea of the wide range of materials research being carried out at the laboratory today.

  3. Reviews

    1. Top of page
    2. Masthead
    3. Essay
    4. Reviews
    5. Communications
    6. Materaials Forum
    7. Research News
    8. Book Reviews
    1. Soluble Oligo- and Polyphenylenes (pages 190–198)

      Prof. James M. Tour

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060303

      Soluble main chain phenylene polymers and oligomers are much less well studied than their intractable relative poly(p-Phenylene). This review considers the synthesis and properties of poly(o-phenylene)s, poly(m-phenylene)s, and substituted polyphenylenes with alkyle-, aryl-, carbonyle-, nitro-, halo-, fused aromatic, and ladder containing substituents, together with related compounds. The figure shows a planar polyphenylene derivative that can be obtained as a flexible free-standing film.

    2. Disorder in Charge Transport in doped polymers (pages 199–213)

      Prof. Mark Van der Auweraer, Prof. Frans C. De Schryver, Dr. Paul M. Borsenberger and Prof. Heinz Bässler

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060304

      Charge transport in molecular doped polymers has important applications in xerography, as well as being a theoretical challenge. Its investigation by determination of transient photocurrents is reviewed, with experiments and pertinent theories, such as hopping in a Gaussian density of states and the small polaron model, being outlined. The temporal features of the photocurrents, the field and temperature dependence of the charge carrier mobilities, and the influence of molecular properties—and what can be inferred from these—are discussed.

  4. Communications

    1. Top of page
    2. Masthead
    3. Essay
    4. Reviews
    5. Communications
    6. Materaials Forum
    7. Research News
    8. Book Reviews
    1. Shear-induced orientation of side-group liquid-crystalline polymers (pages 214–216)

      Dr. Rangaramanujam M. Kannan, Prof. Julia A. Kornfield, Dr. Norbert Schwenk and Dr. Christine Boeffel

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060305

      Side group liquid-crystalline polymers (SG-LCP) will need to be macroscopically oriented if the applications foreseen for them are to be realized. The first observation of oscillatory-sheer-induced alignment of an SG-LCP melt (the Figure shows a schematic of the rheo-optical apparatus used) is reported. This discovery widens the potential applications of SG-LCPs, but also raises fundamental questions regarding the mechanism of flow-induced alignment.

    2. Cooperative magnetic behavior of α- and β-manganese(III) phthalocyanine tetracyanoethenide (1:1), [MnIIIPc]·⊕[TCNE]·⊖ (pages 217–221)

      Dr. Joel S. Miller, Carlos Vazquez, Joseph C. Calabrese, R. Scott McLean and Dr. Arthur J. Epstein

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060306

      Cooperative magnetic interactions have been observed in α-[MnPc][TCNE], which results from the reaction of manganese phthalocyanine with tetracyanoethylene. This is the latest in a series of molecule based materials found to exibit such unusual magnetic behaviour. The α polymorph displays very strong magnetic coupling, while the coupling in β-[MnPc][TCNE] is much weeker. The IR data suggest that the behaviour of the α polymorph is unlikely to be unique among the metallomacrocyclic electron-transfer complexes. It is proposed that uniformity of the one0-dimensional chains in α-[MnPc][TCNE] and the corresponding lack of uniformity of those in the β polymorph may give rise to the difference in behaviour.

    3. High nuclearity magnetic clusters: Magnetic properties of a nine cobalt cluster encapsulated in a polyoxometalate, [Co9(OH)3(H2O)6(HPO4)2(PW9O34)3]16 (pages 221–223)

      Jose Ramón Galán-Mascarós, Dr. Carlos J. Gómez-Garcia, Dr. Juan José Borrás-Almenar and Prof. Eugenio Coronado

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060307

      One goal in molecular magnetism is the synthesis of clusters containing large numbers of coupled spins. In the title heteropolyanion three reconstituted Keggin like fragments [PCo3 W9O40] are assembeled to increase the spin nuclearity. The Figure shows the idealizedstructure of the Co9 cluster, illustrating the connections through oxygen and HPOmath image groups. Magnetic measurements and EPR spectra are presented, and the nature of the cluster ground state discussed.

    4. A novel technique for the preparation of metal clusters in dielectric matrices (pages 223–225)

      Dr. Ryszard Lamber, Dr. Alfred Baalmann, Prof. Nils I. Jaeger, Prof. Günter Schulz-Ekloff and Stefan Wetjen

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060308

      Metal clusters trapped in solid-state matrices can be produced in various wayas. The new method presented here relies on the simultaneous plasma polymerization of a vinyltrimethylsilane monomer and deposition of metal clusters (e.g., Au, Ag, Pd) by an inert gas evaporation technique. The characterization by TEM, XPS, and UV-vis and FTIR spectroscopy of amonorphous plasma-polymer films containing gold clusters is described, which revelas that the clusters areunigorm in size and crystalline.

    5. Passivation of metals by coating with polyaniline: Corrosion potential shift and morphological changes (pages 226–228)

      Dr. Berhard Wessling

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060309

      Corrosion protection of metals can be obtained by coating them with polyaniline dispersions, resulting in a signifiecant and reproducible shift of the corrosion potential. Scanning electron micrograph indicate that the passivation is a multistep process, beginning with an etching stage in wh8ch grain boundaries become visible (see Figure). In the second step the metal surface is coated—non-electrochemically—with an oxide layer. The exact mechanism of formation of this layer remains to be explored.

    6. The deposition of aluminum nitride thin films by metal-organic CVD—an alternative precursor system (pages 229–231)

      Dr. Anthony C. Jones, John Auld, Simon A. Rushworth, Prof. Edward W. Williams, Dr. Peter W. Haycock, Dr. Chiu C. Tang and Dr. Gary W. Critchlow

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060310

      Thin films of aluminum nitride have applications in magnetooptic multilayer structures. Methods must therefore be developed for depositing thin films of this commercially important material at low to moderate substrate temperatures. Conventional CVD riquires a high substrate. The preliminary results presented here show that AIN films grown by metalorganic CVD using Me3Al combined with either tertiary butylamine of isoproplamine, a technique avoiding the above problems, are of sufficient quality for magnetooptical applications. A possible deposition mechanism is proposed.

    7. Electrochemistry of polydialkylcyclopentadithiophenes—modulation of π dimerization by interchain spacing groups (pages 231–233)

      Dr. Gianni Zotti, Dr. Anna Berlin, Prof. Giorgio Pagani, Dr. Gilberto Schiavon and Dr. Sandro Zecchin

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060311

      π dimerization in polythiophenes, leading to stabilization of the intermediate polaronic form, hasrecently been proposed as the origin of the distinctive twin process in the oxidation cycles of polythiophenes. Electrochemical measurements on polymers obtained by anodic cupling 4,4-di-n-alkylcyclopentadithiophene (see Fugure) confirm this; the π dimerization operates when the spacing groups between the polymer strands are absent of the spacing group increases.

  5. Materaials Forum

    1. Top of page
    2. Masthead
    3. Essay
    4. Reviews
    5. Communications
    6. Materaials Forum
    7. Research News
    8. Book Reviews
    1. Materials forum (page 234)

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060312

  6. Research News

    1. Top of page
    2. Masthead
    3. Essay
    4. Reviews
    5. Communications
    6. Materaials Forum
    7. Research News
    8. Book Reviews
    1. CVD routes to titanium disulfide films (pages 237–239)

      Dr. T. Suren Lewkebandara and Prof. Charles H. Winter

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060313

      Tis2 films, used in lithium batteries, can be prepared by a variety of methods, including several chemical vapor deposition (CVD) routs. The available CVD routes are briefly reviewed, together with the techniques used to check that the resulting films meet the stringent requirements of the lithium battery industry, for example. Solid-state lithium batteries used in heart pacemakers require TiS2 thinfilms of high purity, denese packing, exact stoichiometry, and a preferred crystallographic orientation, all of which can be achived by CVD methods.

    2. Rectifying junctions based on metallophthalocyanine thin films (pages 239–242)

      Prof. Dr. William J. Pietro

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060314

      The unusual electrical properties of metallophthalocyanines (M(Pc)S) have made them the centerof much interest recently, in particular as candidates for the fabrication of novel molecularelectronic devices.M(Pc)-basedrectifiers have been known for 20 years, but now a new non-Schottky-type of rectification has been discovered in a junction consisting of Ni(Pc) and Cu(PcF8), see Figure. A brief look is also taken at M(Pc)-based transistorsand future developments.

    3. Pore-size-specific modification of porous materials (pages 242–244)

      Dr. Frantisek Svec and Prof. Jean M. J. Fréchet

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060315

      Pore-size-specific functionalization is a novel approach that allowspreviously undreamed of control of the location of groups undergoing reaction in the surface modigication of preformedporous polymers. That sozespecific functionalization makes possible the simultaneous accommodation of seemingly incompatible requirements is demonstrated by the preparation of porous polyner beads with bimodal surface chemistry. Applications of this technique are foreseen in thechromatographic separation of complex miztures, sensors, catalyses, and eczyme immobilization.

    4. Polymer-protected cu/pd bimetallic clusters (pages 245–247)

      Prof. Naoki Toshima and Dr. Yuan Wang

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060316

      Polymer-protected bimetallic clusters areexcellent candidates as catalysts for various chemical reactions. For Example, Cu/Pd clusters accelerate the hydration of acrylonitrile (See Figure). However, hurdles femain to be overcome in their preparation. Following a brief overview of preparative techniques, details are given of a new method for the preparation of Cu/Pd binetallic clusters protected by poly(N-vinyl-2pyrrolidone) from bimetallic hydroxide colloids.

    5. Prediction of third-order nlo properties of organic molecules (pages 248–251)

      Dr. Dougls S. Dudis, Dr. A. Todd Yeates and Prof. Daniel Kost

      Article first published online: 15 SEP 2004 | DOI: 10.1002/adma.19940060317

      Organic materials with large nonlinear optical (NLO) responses will be important in the development of photonic technology. In the search for such materials, the ability topredict the NLO responses of molecules will be invaluable. Techniques for the computation of the second-order hyperpolarizability γ aredescribed, including molecularorbitalk models, semiempirical nethods, andab initio methods, The effects of structure on γ are discussed, together withthe remarkablelresult that in three classes of simple compounds γ can be linearly correlated with molecular mass, regardless of the polarity of the compounds.

  7. Book Reviews

    1. Top of page
    2. Masthead
    3. Essay
    4. Reviews
    5. Communications
    6. Materaials Forum
    7. Research News
    8. Book Reviews

SEARCH

SEARCH BY CITATION