Temperature-dependent aggregation behavior of symmetric long-chain bolaamphiphiles at the air-water interface

The behavior of the symmetric long-chain bolaamphiphiles dotriacontane-1,32-diyl bis[2-(trimethylammonio)ethyl phosphate] (PC-C32-PC), and dotriacontane-1,32-diyl bis[2-(dimethylammonio)ethyl phosphate] (Me(2)PE-C32-Me(2)PE) at the air-water interface was investigated by means of temperature-depende...

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Veröffentlicht in:Langmuir : the ACS journal of surfaces and colloids. - 1992. - 22(2006), 6 vom: 14. März, Seite 2668-75
1. Verfasser: Köhler, Karen (VerfasserIn)
Weitere Verfasser: Meister, Annette, Dobner, Bodo, Drescher, Simon, Ziethe, Friederike, Blume, Alfred
Format: Aufsatz
Sprache:English
Veröffentlicht: 2006
Zugriff auf das übergeordnete Werk:Langmuir : the ACS journal of surfaces and colloids
Schlagworte:Journal Article
Beschreibung
Zusammenfassung:The behavior of the symmetric long-chain bolaamphiphiles dotriacontane-1,32-diyl bis[2-(trimethylammonio)ethyl phosphate] (PC-C32-PC), and dotriacontane-1,32-diyl bis[2-(dimethylammonio)ethyl phosphate] (Me(2)PE-C32-Me(2)PE) at the air-water interface was investigated by means of temperature-dependent film-balance measurements and Brewster angle microscopy. Upon compression of the monolayer the isotherms show a strong surface pressure increase. We assume that at high pressure the monolayer consists of molecules in a reversed U-shaped conformation. At an area of 0.9-1.1 nm(2) per molecule a plateau is reached for both bolaamphiphiles, which marks the beginning of an aggregate formation on the water surface. The plateau pressure increases with increasing temperature. For PC-C32-PC at 6.7 degrees C curved shorter fibrous domains with a diameter of 20-30 mum are seen on the water surface, whereas at 29.2 degrees C stripelike domains with a thickness of 200-500 mum are observed. Isotherms recorded within this temperature range show a characteristic break within the steep slope marking a region where a mixture or a hybrid form of both structures exists. Me(2)PE-C32-Me(2)PE in its zwitterionic state at low pH forms microcrystals on the water surface, whose formation is kinetically retarded. Depending on the temperature, the aqueous subphase is more or less homogeneously covered with a crystalline-like film. In contrast, no aggregates are observed at pH 10 when the bolaamphiphile is negatively charged
Beschreibung:Date Completed 26.02.2007
Date Revised 07.03.2006
published: Print
Citation Status PubMed-not-MEDLINE
ISSN:1520-5827