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  • 1
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    Materials science. Playing nature's game with artificial muscles (2005)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2005-04-02
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Baughman, Ray H -- New York, N.Y. -- Science. 2005 Apr 1;308(5718):63-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉NanoTech Institute and Department of Chemistry, University of Texas at Dallas, Richardson, TX 75083, USA. ray. baughman@utdallas.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15802593" target="_blank"〉PubMed〈/a〉
    Keywords: *Artificial Organs ; Biomechanical Phenomena ; *Biomimetic Materials ; Elastomers ; Electric Capacitance ; Electric Conductivity ; Electrochemistry ; Electrodes ; *Muscles/physiology ; Nanostructures ; Nanotubes, Carbon ; *Polymers ; Robotics ; Static Electricity ; Stress, Mechanical
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 2
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    Fuel-powered artificial muscles (2006)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2006-03-18
    Description: Artificial muscles and electric motors found in autonomous robots and prosthetic limbs are typically battery-powered, which severely restricts the duration of their performance and can necessitate long inactivity during battery recharge. To help solve these problems, we demonstrated two types of artificial muscles that convert the chemical energy of high-energy-density fuels to mechanical energy. The first type stores electrical charge and uses changes in stored charge for mechanical actuation. In contrast with electrically powered electrochemical muscles, only half of the actuator cycle is electrochemical. The second type of fuel-powered muscle provides a demonstrated actuator stroke and power density comparable to those of natural skeletal muscle and generated stresses that are over a hundred times higher.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ebron, Von Howard -- Yang, Zhiwei -- Seyer, Daniel J -- Kozlov, Mikhail E -- Oh, Jiyoung -- Xie, Hui -- Razal, Joselito -- Hall, Lee J -- Ferraris, John P -- Macdiarmid, Alan G -- Baughman, Ray H -- New York, N.Y. -- Science. 2006 Mar 17;311(5767):1580-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry and NanoTech Institute, University of Texas at Dallas, Richardson, TX 75083-0688, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16543453" target="_blank"〉PubMed〈/a〉
    Keywords: *Artificial Organs ; Biomechanical Phenomena ; *Biomimetic Materials ; Bionics ; Electric Power Supplies ; Electrochemistry ; *Electrodes ; Hydrogen/chemistry ; Lifting ; *Muscle, Skeletal/physiology ; *Nanotubes, Carbon ; Oxidation-Reduction ; Oxygen/chemistry ; Robotics ; Stress, Mechanical
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
    Electronic Resource
    Electronic Resource
    Deformation and microstructure of extended-chain polydiacetylene crystals (1975)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 13 (1975), S. 1871-1879 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The mechanical properties (Young's modulus, ultimate tensile strength, deformation processes) of extended-chain polydiacetylene crystals are investigated. The properties observed are similar to those of metal and ceramic whiskers. The elastic modulus is strain-dependent and the ultimate tensile strength increases with decreasing crystal size. The maximum tensile strength observed was 1700 Nmm-2. The ultimate tensile strength seems to be controlled by the presence of a small number of defects near the surface at which fracture nucleates. Irreversible deformation of the crystals was observed to occur by crack propagation normal and parallel to the direction of the macromolecules. The observed mechanical behavior corresponds to exceptionally high per-chain properties. The per-chain modulus obtained for these crystals is nearly as high as that of diamond. A chain-aligned polyethylene fiber with the same per-chain mechanical properties would have an ultimate strength as high as 0.9 × 104 Nmm-2.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1975.180131002
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  • 4
    Electronic Resource
    Electronic Resource
    Negative thermal expansion of a polydiacetylene single crystal (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 11 (1973), S. 2453-2466 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Macroscopic thermal expansion in the chain direction has been measured for the first time on organic polymeric single crystals. Negative linear thermal expansion coefficients αM are reported and related to chain torsional motion and equilibrium point-defect formation for a solid-state polymerized phase of 2,4-hexadiyne-1,6-diol bisphenylurethane (HDU) which contains crystallographically located interstitial dioxane and for a dioxanefree phase obtained by thermal annealing. Data for as-polymerized single crystals (which are probably of extended chain morphology) between -50 and 100°C give αM = -(1.686 ± 0.039) × 10-5 - (1.35 ± 0.18) × 10-7 t with t in °C. During volatilization of 11.7 ± 1.0 wt-% interstitial dioxane and a resulting crystal structure change, the as-polymerized fibers fibrillate and shrink irreversibly by 0.16 ± 0.04%. Although dichroism and diffraction measurements indicate both a high degree of crystallinity and chain alignment for the dioxane-free phase, the average thermal expansion coefficient, (-3.0 ± 1.0) × 10-6 °C-1 between -50 and 150°C, is about an order of magnitude less than for the as-polymerized single crystals.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1973.180111213
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  • 5
    Electronic Resource
    Electronic Resource
    Relevance of cage recombination in the plastic deformation of polymers (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 11 (1973), S. 2441-2451 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: For a polymer in which permanent rupture of individual molecules is the rate-limiting process for plastic deformation, the kinetics of chain-end diffusion and secondary radical reactions should be compared with the kinetics of caged radical recombination in the calculation of activation parameters for plastic deformation. If mechanisms of cage escape are slower than those for cage recombination, the activation parameters for plastic deformation will differ from those for the initial bond-breaking process. For the case of polyethylene deformed in the vicinity of 250°K, the critical thermally activated event appears to involve scission of the polymer molecule near the site of an abstracted hydrogen atom. For this system the dominant cage-escape mechanism is diffusion, which is faster than either hydrogen abstraction or unzipping to the monomer. However, at low stresses the rate of cage recombination is expected to be higher than the rate of cage escape, so that the activation parameters for deformation should be the sum of those for chain scission and diffusion. The contribution of diffusion (ca. 15 kcal/mole) to the activation energy for deformation (E*, extrapolated to zero stress conditions) is relatively modest. However, the calculated molar activation volume for deformation V* increases by almost an order of magnitude, i.e., from ca. 10 to ca. 76 cm3/mole when diffusion is required. Consideration of experimental values of E* and V* for high molecular weight polyethylene indicates that, in the regime examined, chain scission plus chain-end diffusion is required to effect plastic deformation.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1973.180111212
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  • 6
    Electronic Resource
    Electronic Resource
    Electron delocalization contribution to single crystal thermal expansion of a polydiacetylene (1974)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 12 (1974), S. 2189-2193 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermal expansion contribution due to temperature-dependent π-electron delocalization is evaluated from spectral measurements on a single crystal polydiacetylene (poly-2,4-hexadiyne-1,6-diol bisphenylurethane). The observed temperature independence of backbone associated vibrations (less than ±1 cm-1 change in νC=C and νC≡C between 25 and 90°C) implies that thermal conformational fluctuations and equilibrium defect formation (which produce a negative thermal expansion coefficient) do not measurably affect π-electron delocalization. The separation of equilibrium defects is either much longer than that of nonequilibrium defects or much longer than required to appreciably limit π-electron delocalization in an effectively defect-free polymer. Arguments presented indicate that, in the experimental temperature interval, the observed thermal expansion coefficient in the chain direction is over an order of magnitude larger than the delocalization-associated contribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1974.180121102
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  • 7
    Electronic Resource
    Electronic Resource
    Comments on the optical properties of fully conjugated polymers: Analogy between polyenes and polydiacetylenes (1976)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 2037-2045 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The similarity of the π-electron backbones of the polyenes and the polydiacetylenes suggests an analogy between these two fully conjugated, linear polymers. The extent of the analogy is discussed through the examination of a series of model compounds: the polyenes and the polyenynes. The optical band gaps and the polarizabilities of polyenynes are compared to those of the polyenes and to the predictions of a modified free-electron model. It is concluded that the chain-dependent electronic properties of the polyenes may be extrapolated with some confidence to the polydiacetylenes.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1976.180141109
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  • 8
    Electronic Resource
    Electronic Resource
    The nature and origin of structural defects in polymeric sulfur nitride (1976)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 2019-2035 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Defect structures in (SN)x crystals obtained by solid-state polymerization are so numerous and varied that they are likely to conceal inherent property aspects of the defect-free polymer. In addition to frequent macroscopic twinning, three different kinds of defect sites are observed. These sites are related to the disruption of molecular orientational order about the chain axis direction and the sequencing of chain types in the periodic phase. The origin of these defects is explained by the nonuniqueness of solid-state polymerization and recrystallization processes, which transform the initial dimer phase to the final polymer phase. The orientational relationship between the dimer and polymer phase is predicted from the observed twinning mode and the structural relationship between these phases. The change from dimer phase (at zero and at intermediate conversions involving solid solution formation) to polymer phase can be described by a shear transformation on the (001) dimer plane. This observation suggests an analogy with known martensitic reactions and a method for improving the perfection of (SN)x.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1976.180141108
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  • 9
    Electronic Resource
    Electronic Resource
    Raman spectral changes during the solid-state polymerization of diacetylenes (1973)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 11 (1973), S. 603-619 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Raman spectral changes resulting from the solid-state 1,4-addition polymerization of conjugated diacetylenes are reported. The monomers show an intense C≡C stretching frequency near 2260 cm-1, where as the polymers showed two strong bands, a C≡C vibration near 2100 cm-1 and a C=C vibration near 1500 cm-1. The presence of both double and triple bonds in the polymers suggests the backbone structure (=C—C≡C—C=)n. The alternate mesomeric structure (—C=C=C=C—)n can be eliminated as a possibility by the presence of the strong C≡C vibration in the polymer. Sequential Raman spectra obtained during radiation-induced polymerization revealed intermediate spectral states between the initial monomer and final polymer. Intermediate-state vibrations first increase and then decrease in intensity as polymerization proceeds. However, the observed vibtrational frequencies of intermediate states were not dependent upon the extent of polymerization. Whether polymerization occurred thermally or as a result of radiation did not appear to influence the spectrum of the final polymer, but the observed number of intermediate states differed. Polymerization mechanisms, required molecular motions, and resulting structural changes are discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1973.180110401
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  • 10
    Electronic Resource
    Electronic Resource
    Solid-state synthesis of large polymer single crystals (1974)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 12 (1974), S. 1511-1535 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Criteria for the solid state synthesis of large, nearly defect-free, polymer crystals are derived and related to experimental observations. Polydiacetylene single crystals are of principal concern, although the concepts presented can be easily generalized. In particular, a least-motion criterion is developed whereby the solid-state reactivity of different diacetylene phases and the most likely polymerization mode of a particular phase can be predicted from a two-parameter description of the relationship between neighboring monomer molecules. Phase stability criteria are considered for four characteristic free energy diagrams which explain the phase behaviors that have been observed for various polymerizing diacetylenes. Reaction uniqueness criteria are discussed as they relate to monomer site point group symmetry, symmetry relations between mutually reacting monomer molecules, and dimensional changes during polymerization.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1974.180120801
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