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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 16 (1995), S. 33-43 
    ISSN: 1572-9567
    Keywords: free-standing film ; heat capacity ; layer-by-layer transition ; liquid crystal ; smectic-A hexatic-B transition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Employing our free-standing film calorimetric system. we have identified three remarkable layer-by-layer transitions in several liquid crystal compounds. Each of these transitions can be well described by the simple power-law form:L = L 0 t. The layering transitions liMind near the smectic-A- hexatic-B and smectic-A crystal-B transitions are well characterized by the exponent v≈ 1 3. This value is consistent with models based on a van der Wads-like dominant intermolecular interaction. Another novel layer-by-layer thinning transition has been discovered above the hulk smectic-A isotropic transition of a perfluorinated liquid crystal compound. The value of the exponent obtained, v ≈ 3 4. cannot he easily explained using familiar models.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    International journal of thermophysics 15 (1994), S. 1189-1197 
    ISSN: 1572-9567
    Keywords: calorimeter ; density ; film ; heat capacity ; hexatic ; liquid crystal ; smectic-A-hexatic-B transition ; two-dimensional melting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A state-of-the-art calorimetric system has been established. The system enables us to measure simultaneously heat capacity and optical reflectivity of free-standing liquid-crystal films from many hundreds down to only two molecular layers in thickness. Our experimental results on the smectic-A-hexatic-B and smectic-C-smectic-I transitions cannot be described solely in terms of the creation of bond-orientational order, indicating that additional molecular order must be present in the hexatic phases of liquid crystals.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 357-366 
    ISSN: 0887-624X
    Keywords: surface graft copolymerization ; adhesive-free adhesion ; polycarbonate ; XPS ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The surfaces of ozone-pretreated polycarbonate films were subjected to further modification by thermally induced graft copolymerization with acrylic acid (AAc), sodium salt of styrene sulfonic acid (NaSS), N,N-dimethylacrylamide (DMAA), N,N-(dimethylamino)ethyl methacrylate (DMAEMA) and 3-dimethyl(methacryloyl ethyl)-ammonium propanesulfonate (DMAPS) monomers. The structure and composition at the copolymer interface were studied by angle-resolved X-ray photoelectron spectroscopy (XPS). For polycarbonate films with a substantial amount of grafted polymer, the hydrophilic graft penetrates or becomes partially submerged beneath a thin surface layer of dense substrate chains. This microstructure was further supported by the water contact angle measurements. Adhesive-free adhesion studies revealed that the AAc, DMAA or DMAPS graft copolymerized polycarbonate film surface adhered strongly to another similarly modified surface (homo-interface) when brought into direct contact in the presence of water and subsequently dried. The development of the lap shear strength is dependent on the concentration of the surface graft, the microstructure of the grafted surface, the adhesion (drying) time, and the nature of the interfacial interaction. The simultaneous presence of chain entanglement and electrostatic interaction readily results in substantially enhanced adhesion strengths between two DMAPS graft copolymerized surfaces or between an AAc and a DMAA graft copolymerized surface (hetero-interface). XPS analyses of the delaminated surfaces suggest that failure occurred cohesively below the graft-substrate interface. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 357-366, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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