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  • Electronic Resource  (5)
  • 1995-1999  (5)
  • Polymer and Materials Science  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Polymer chain organization and orientation in ultrathin films: A spectroscopic investigation (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 2335-2349 
    Details
    ISSN: 0887-6266
    Keywords: morphology ; polysilanes ; thin film ; chain orientation ; spectroscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effect of confinement on the crystallinity and chain orientation of ultrathin poly(di-n-hexylsilane) films has been investigated using UV absorption, fluorescence and IR spectroscopies. UV absorption measurements in a series of poly(di-n-hexylsilane) films having thicknesses between 50 and 3500 Å have shown that, for thicknesses less than 500 Å, the polymer backbone disorders and extensive crystallization of the films is hindered irrespective of molecular weight or surface hydrophobicity. Fluorescence studies showed that rapid energy transfer occurs from the disordered chain segments to the crystalline ones. The orientation of both the polymer backbone and side chains was probed with IR absorption and grazing incidence reflection measurements. The side chains are extended, although not completely in the all-trans conformation, with their carbon plane mostly perpendicular to the substrate. The backbone lies extended, with the polymer axis parallel to the plane of the film. The hexyl side-chains disorder in films less than 2000 Å thick and this disordering occurs through the introduction of gauche bonds. Our findings suggest the possibility of using thickness to control the chain organization and morphology of a polymer thin film. © 1996 John Wiley & Sons, Inc.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Transmission electron microscopy of 3F/PMDA-polypropylene oxide triblock copolymer based nanofoams (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1067-1076 
    Details
    ISSN: 0887-6266
    Keywords: transmission electron microscopy ; block copolymer ; polyimide ; nanofoam ; porous films ; polymer foam ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Transmission electron microscopy was performed on a polymeric nanofoam material, derived from a triblock copolymer composed of a fluorinated polyimide center block, 3F/PMDA (derived from pyromelletic dianhydride (PMDA) and 1,1-bis(4-aminophenyl)-1-phenyl-2,2,2-trifluoroethane (3F)) and polypropylene oxide (PO) end blocks. The cast and imidized polymer exhibits a microphase-separated morphology consisting of PO microdomains within a polyimide matrix. The final nanofoam material is obtained by decomposing PO microdomains into low molecular weight products, which diffuse out of the polyimide matrix leaving nanometer length scale voids. Ruthenium tetroxide staining prior to microscopy was used to enhance the contrast between the 3F/PMDA matrix and the PO microdomains or voids, which permitted a more detailed view of the microstructure of both the foamed and unfoamed materials. From the power spectra of the micrographs, spatial correlation between the PO microdomains in the unfoamed material and between the voids in the foam were found. An interdomain separation distance of ca. 37 nm was observed. Analysis of the image yielded an average area of 411 nm2 for the PO domains. The analysis indicated that the PO domains were oblong, having average major and minor dimensions of 35 and 12.5 nm, respectively. An autocorrelation of the image showed that the domain center of masses were positioned 41 nm apart, in close agreement with the domain spacing (ca. 37 nm) found as described above. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1067-1076, 1997
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Molecular probe techniques for studying diffusion and relaxation in thin and ultrathin polymer films (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2795-2802 
    Details
    ISSN: 0887-6266
    Keywords: ultrathin polymer films ; fluorescence nonradiative energy transfer ; second harmonic generation ; polymer relaxation ; small-molecule diffusion ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Two optically based, molecular probe techniques are employed to study relaxation and small-molecule translational diffusion in thin and ultrathin (thicknesses 〈 ∼200 nm) polymer films. Second harmonic generation (SHG) is used to study the reorientational dynamics of a nonlinear optical chromophore, Disperse Red 1 (DR1) (previously shown to be an effective probe of α-relaxation dynamics) either covalently attached or freely doped in polymer films. Our studies on films ranging in thickness from 7 nm to 1 μm show little change in Tg with film thickness; however, a substantial broadening of the relaxation distribution is observed as film thickness decreases below approximately 150 nm. Experimental guidelines are given for using fluorescence nonradiative energy transfer (NRET) to study translational diffusion in ultrathin polymer films. Appropriate choice of a fluorescence donor species is important along with ensuring that diffusion is slow enough to be measured appropriately. Initial results on the diffusion of a small-molecule probe, lophine, in poly(isobutyl methacrylate) indicates that there is little change in probe diffusion coefficients in films as thin as 90 nm as compared to bulk films. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2795-2802, 1997
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    Application of solubility parameter theory to dentin-bonding systems and adhesive strength correlations (1998)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 41 (1998), S. 237-243 
    Details
    ISSN: 0021-9304
    Keywords: solubility parameters ; dentin ; adhesives ; interpenetrating polymer networks ; bioadhesives ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The principal aim of this study was to investigate the relationships between the solubility parameters of etched dentin, and adhesive primer solutions and adhesive bond strength. Solubility parameters characterize the molecular interactions which determine physical properties such as wetting, and thus can serve as tools to aid development of polymeric adhesives and interpenetrating polymer networks. If an adhesive monomer has a solubility parameter close to that of a polymer substrate, then the monomer may act as a solvent for the polymer and penetrate below the surface. Subsequent polymerization of the monomer may then produce an interpenetrating network, thus adhering without necessarily forming primary chemical bonds to the substrate. The dentin substrate considered in this study was abraded dentin treated with ethylenediaminetetraacetic acid. Solubility parameters δp, δh, and δd calculated for the etched dentin substrate were 20.3, 23.6, and 16.0 (J/cm3)1/2, respectively. Solubility parameters of the primers were expressed using Hansen's three-dimensional scheme. The data indicate a correlation between the calculated solubility parameters of the etched dentin, and dentin primers and the resulting bond strengths. The results corroborate the significance of solubility parameter considerations for adhesive bonding to dentin. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 41, 237-243, 1998.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    Surface orientation of liquid crystalline poly(alkylsilanes) (1995)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 46 (1995), S. 60-63 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: X-ray diffraction measurements on thin films of poly(hexyl-pentylsilane) cast on silicon substrates are presented. The polymer chains pack in a hexagonal lattice which is oriented such that the chains lie parallel to the surface. In addition, a remarkable degree of orientational order was found with the planes containing the neighbor molecules lying in the surface plane. Parallel to the film surface, the average crystallite size is 600 Å, while perpendicular to the surface, there is nearly perfect interchain stacking of the polymers throughout the thickness of the film.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1995.010460108
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