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  • 1
    Electronic Resource
    Electronic Resource
    Influence of ligand structure and solvent effects on complexation of neutral guests by several crown ethers (1994)
    Springer
    Journal of solution chemistry 23 (1994), S. 53-61 
    Details
    ISSN: 1572-8927
    Keywords: Crown ethers ; benzocrown ethers ; non-charged complexes ; host-guest complexes ; calorimetric titration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The formation of complexes between crown ethers and acetonitrile, chloroform, and nitromethane were investigated in carbon tetrachloride at 25°C. A significant influence of the ring size on the selectivity of the host is evident. The host 18-crown-6 forms complexes for which the reaction enthalpy and entropy are quite high. Host molecules with benzene side groups form complexes of lower reaction enthalpy and entropy and therefore the complexes formed are less stable than that of the analogous crown ethers without aromatic groups. Solvent effects on the stability constant K, the reaction enthalpy ΔH, and the reaction entropy ΔS were studied for the complexation of malonitrile by 18-crown-6. The reaction enthalpy and entropy values change in accordance with the dielectric constant of the solvent used, but no overall effect on complex stability with change in solvent dielectric constant was observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00972607
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  • 2
    Electronic Resource
    Electronic Resource
    The effect of vacuum-ultraviolet laser wavelengths on the surface treatment of polyolefinic polymers (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 887-890 
    Details
    ISSN: 0887-6266
    Keywords: surface modification ; UV-F2-excimer laser ; stress field ; surface morphology ; fibers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The laser-induced modification of the surface morphology of poly(propylene) fibers and films was investigated. It is known that strongly absorbing fibers such as poly(ethylene terephthalate) and polyamide obtain characteristic surface morphologies after treatment with 193 or 248 nm laser irradiation. Polyolefinic material cannot be modified directly (i.e., without doping) by irradiation with these wavelengths. Therefore experiments were carried out using a 157 nm F2-laser. After irradiation in a vacuum chamber at fluences in excess of 50 mJ/cm2 poly(propylene) also reveals the well-known surface morphology. Compared with aromatic polymers a rather high number of pulses is needed to generate the effect. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1993.090310717
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