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  • 1
    Electronic Resource
    Electronic Resource
    Effect of chain length on the glyme-separated ion-pair formation in bolaform salts of α,ω-(9-fluorenyl)polymethylenes (1978)
    Springer
    Journal of solution chemistry 7 (1978), S. 9-18 
    Details
    ISSN: 1572-8927
    Keywords: Optical spectroscopy ; bolaform electrolytes ; ion pairs ; ion-pair aggregation ; glyme-separated ion pairs ; α,ω-(9-fluorenylsodium)-polymethylenes ; fluorenylsodium ; tetraglyme ; tetrahydrofuran ; tetrahydropyran
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Formation constants of tetraglyme (glyme 5) separated ion pairs of bolaform electrolytes of the type Na+,−Fl(CH2) n Fl−, Na+ (Fl− denoting a fluorenyl carbanion) were measured spectrophotometrically in tetrahydrofuran (THF) and tetrahydropyran (THP) at 25°C as a function of the chain lengthn, withn=2, 3, 4, or 6. The ratiosK 1/K 2 of the first and second glyme ion-pair separation steps were found to be equal to the statistical factor 4 in all cases except in THP for the compoundn=2, where the ratio is 15. Values ofK 1 as well as K 2 increase considerably with chain length, the former by a factor 19 asn increases from 2 to 6. The ion-pair separation with glyme 5 is easier in THP than in THF. The results are discussed in terms of differences in external cation solvation and the possible involvement of cyclized structures or curled conformations as a result of interactions between the terminal ion pairs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00654214
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Ion binding properties of poly(ethylene oxide)-based networks in dioxane and toluene (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 1819-1824 
    Details
    ISSN: 0887-624X
    Keywords: poly(ethylene oxide) networks ; alkali picrates ; alkali ion binding ; poly(crown ether) ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Binding constants of alkali picrates to poly(ethylene oxide)-based networks were measured spectrophotometrically in dioxane at 25 and 40°C. The networks were synthesized from aliphatic tri- or tetrafunctional isocyanates and α,ω-diamino-poly-(ethylene glycol)s. The slopes of the Klotz binding plots appear to decrease in the lower picrate concentration range, suggesting that binding of the salt becomes more difficult at high picrate content. It was shown that under saturation conditions six to seven ethylene oxide units are required to bind a sodium picrate ion pair. The affinity of the PEO-resins for the alkali picrate can be enhanced by immobilizing a poly(crown ether) in the network. A number of competition experiments for sodium picrate in toluene was also carried out to obtain the affinity of soluble ligands for alkali salts. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1819-1824, 1997
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
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