title: Evidence for a reverse U-shaped conformation of single-chain bolaamphiphiles at the air-water interface.
abstract: Infrared reflection absorption spectroscopy and X-ray reflectivity have been used to elucidate the molecular orientation and hydrocarbon chain conformation and packing of the symmetric long-chain bolaamphiphiles dotriacontane-1,1'-diyl-bis-[2-(trimethylammonio)ethylphosphate] (PC-C32-PC) and dotriacontane-1,1'-diyl-bis-[2-(dimethylammonio)ethylphosphate] (Me2PE-C32-Me2PE) at the air-water interface. At low surface pressures, these bipolar amphiphiles are found to lie flat on the water surface with a disordered chain. With increasing surface pressure, the alkyl chain becomes more ordered. Concomitantly, the chain is bent pointing into the air, whereas both polar headgroups keep contact with the water subphase. At an area of 0.9-1.1 nm2 per molecule, a surface pressure plateau is reached for both bolaamphiphiles, where the molecules adopt a reverse U-shaped conformation with a strongly tilted alkyl chain. Further compression leads to the formation of 3-D aggregates.
authors: Institute of Chemistry, Martin-Luther-University Halle-Wittenberg, Mühlpforte 1, 06108 Halle, Germany.
authors: Annette
authors: A
authors: Meister
authors: Marcus J
authors: MJ
authors: Weygand
authors: Gerald
authors: G
authors: Brezesinski
authors: Andreas
authors: A
authors: Kerth
authors: Simon
authors: S
authors: Drescher
authors: Bodo
authors: B
authors: Dobner
authors: Alfred
authors: A
authors: Blume