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  • Digitale Medien  (2)
  • Optical spectroscopy  (1)
  • t-butyl methacrylate  (1)
  • 1
    ISSN: 1572-8927
    Schlagwort(e): Optical spectroscopy ; bolaform electrolytes ; ion pairs ; ion-pair aggregation ; glyme-separated ion pairs ; α,ω-(9-fluorenylsodium)-polymethylenes ; fluorenylsodium ; tetraglyme ; tetrahydrofuran ; tetrahydropyran
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: 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.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 363-368 
    ISSN: 0887-624X
    Schlagwort(e): 2-vinylpyridine ; t-butyl methacrylate ; anionic polymerization ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The synthesis of well defined and monodisperse (Mw/Mn ≤ 1.2) narrow molecular weight distribution poly (2-vinylpyridine)-poly (t-butyl methacrylate) (P2VP-PTBMA) AB block copolymers is carried out by initiation of 2-vinylpyridine polymerization by 1,1-diphenylhexyllithium in THF at-78°C, followed by addition of TBMA and termination at -78°C using MeOH. The formation of the BAB block copolymer is carried out in a similar fashion except that 1,4-dilithio-1,1,4,4-tetraphenylbutane is used as initiator. The corresponding synthesis of P2VP-PMMA block copolymers is carried in a similar manner, except that 1-2 equivalents of TBMA is used to end-functionalize the living P2VP before the addition of MMA. Without the addition of TBMA, trimodal molecular weight distributions in P2VP-b-PMMA are obtained. All the block copolymers are characterized by Size Exclusion Chromatography (SEC), Nuclear Magnetic Resonance (NMR), and Differential Scanning Calorimetry (DSC). © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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