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  • 1
    Electronic Resource
    Electronic Resource
    Ion Pair Amphiphiles from Sodium Dodecyl Sulfate and Ammonium Amphiphiles Carrying Functionalized Azobenzene Units (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1719-1724 
    Details
    ISSN: 0947-3440
    Keywords: Thermotropic and lyotropic phase behavior ; Amphotropes ; Surfactants ; Liquid crystals ; Chromophores ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New ammonium amphiphiles having a N,N-dimethyl-N-hydroxyethylammonium headgroup and various azobenzene mesogenic units connected by a decyl or dodecyl spacer have been synthesized. The azobenzene unit is functionalized at the 4-position with a cyano, methoxy or fluoro substituent. For the cyano-substituted amphotropes and the fluoro compound with a dodecyl spacer a smectic phase is formed as was observed by differential scanning calorimetry and polarization microscopy. Complexation with sodium dodecyl sulfate, SDS, in a 1:1 molar ratio induces the formation of a smectic phase for the compounds with a decyl spacer. The compounds with a dodecyl spacer showed rather complex behavior attributed to different crystal morphologies. The ammonium amphotropes form aggregates in water when heated above their Krafft temperature. However, these aggregates are not stable and crystallize upon cooling. The ion pair amphiphiles with SDS as second component form vesicles in water as observed by optical and electron microscopy. The observed blue shift in the UV absorption maximum of the amphotropes upon addition of SDS indicates π-π stacking between mesogenic units resulting from aggregation.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970813
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  • 2
    Electronic Resource
    Electronic Resource
    Interactions between Chromophore-Labelled Ammonium Surfactants and Hydrophobically Modified Polyelectrolytes (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 305-312 
    Details
    ISSN: 1434-193X
    Keywords: UV spectroscopy ; Poly(maleic acid-co-alkyl vinyl ether)s ; Azobenzene ; (Cyanobiphenylyl)oxy ; Cooperative binding ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The interaction of poly(maleic acid-co-alkyl vinyl ether)s and poly(sulfonylethyl maleic acid monoamide-co-alkyl vinyl ether)s with and without (cyanobiphenylyl)oxy chromophores with N-[ω-(substituted azobenzoxy)alkyl]-N,N-dimethyl-N-hydroxyethylammonium bromide surfactants has been studied by UV spectroscopy. The azobenzene unit is functionalized at the 4′-position with a cyano or fluoro substituent and is connected to the surfactant headgroup via a decyl or dodecyl spacer. Upon addition of surfactants to poly(maleic acid-co-butyl vinyl ether) the absorption maxima (λmax) of the azobenzene chromophores immediately show their maximum blue shift. This indicates cooperative binding of surfactant to this polymer, and the formation of micelle-like aggregates surrounded by polyelectrolyte is assumed. Upon addition of the surfactants to the other polyelectrolytes λmax values of the azobenzoxy chromophores gradually shift to lower values indicating a lower cooperativity of surfactant binding. This is attributed to the formation of microdomains by the polyelectrolytes themselves. For these systems the formation of mixed micelles is assumed. The compactness of the microdomains of the maleic acid copolymers is influenced by the pH and binding with surfactants is also influenced by pH. The sulfonylethyl maleic acid monoamide copolymers show no pH dependence in binding above neutral pH. For these polyelectrolytes the cooperativity also becomes less with a longer spacer between backbone and chromophore. Upon elongation of the surfactant spacer or changing the end group from a cyano to the more hydrophobic fluoro substituent a lower λmaxis observed for the chromophores upon initial binding to the polyelectrolytes indicating more cooperative binding. When surfactants and polyelectrolytes are both labelled with chromophores, binding proceeds noncooperatively and the formation of mixed micelles is assumed.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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