ESCA studies of phase-transfer catalysts in solution: ion pairing and surface activity

Choline carboxylate surfactants are powerful alternatives to the well-known classical alkali soaps, since they exhibit substantially increased water solubility while maintaining biocompatibility, in contrast to simple quaternary ammonium ions. In the present study, we report the aqueous binary phase diagrams and a detailed investigation of the lyotropic liquid crystalline phases formed by choline carboxylate surfactants (ChCm) with chain lengths ranging from m ¼ 12-18 and at surfactant concentrations of up to 95-98 wt%. The identification of the lyotropic mesophases and their sequence was achieved by the penetration scan technique. Structural details are elucidated by small-angle X-ray scattering (SAXS). The general sequence of mesophases with increasing soap concentration was found to be as follows: micellar (L 1 ), discontinuous cubic (I 1 ), hexagonal (H 1 ), bicontinuous cubic (V 1 ) and lamellar (L a ). The main difference to the phase behavior of alkali soaps or of other mono-anionic surfactants is the appearance and large extent of a discontinuous cubic phase with two or even more different symmetries. The obtained phase diagrams further highlight the extraordinarily high water solubility of ChCm soaps. Finally, structural parameters of ChCm salts such as the cross-sectional area at the polarnonpolar interface are compared to those of alkali soaps and discussed in the terms of specific counterion binding and packing constraints.

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“…38 Upon addition of two CH 2 groups, r L increases at a given volume fraction by about 1.5-2. 4 A, which complies with reported values.…”

Section: Hexagonal Phase Hsupporting

confidence: 92%

“…[4][5][6][7] By contrast, the use of choline as a quaternary ammonium ion of biological origin sustains biocompatibility.…”

Section: 2mentioning

confidence: 99%

Aqueous phase behaviour of choline carboxylate surfactants—exceptional variety and extent of cubic phases

et al. 2011

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“…Smaller TAA cations are also used in technology as phase transfer catalysts (e.g., tetrabutylammonium (TBA) cations) [17]. As such they can transport small ions across biological tissues, which explains their potential toxicity, and they can also block cellular ion channels [18,19].…”

Section: Introductionmentioning

confidence: 99%

Selected biologically relevant ions at the air/water interface: A comparative molecular dynamics study

Hrobárik

Vrbka

Jungwirth

2006

Biophysical Chemistry

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“…Siegbahn et al have prepared a liquid flow in vacuum and measured a kinetic energy distribution of X-ray photoelectrons. [1][2][3][4][5][6][7][8] Delahay et al [9][10] and Ballard et al [11][12][13][14][15] have observed electronic structures of the molecules in the vicinity of a liquid surface by ultraviolet photoelectron spectroscopy. Penning electron spectra of the outermost layer of a liquid surface of formamide have also been measured by Morgner et al 16,17 On the other hand, Faubel et al have measured a kinetic energy distribution of molecules evaporating from a liquid surface and elucidated that they are forced by a local strain exerted each other.…”

Section: Introductionmentioning

confidence: 99%

Ion−Molecule Reactions in a Liquid Beam of Methanol, Ethanol, and 1-Propanol following Multiphoton Ionization

1996

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Methanol, ethanol, or 1-propanol was introduced into vacuum as a continuous liquid flow (liquid beam) and was subjected to nonresonant multiphoton ionization under irradiation of a 270 nm laser. Ions ejected into vacuum were mass-analyzed by means of time-of-flight mass spectrometry, where the ions were extracted by a static electric field, or a pulsed electric field with a delay time of ∼1.6 µs with respect to a pulse laser. Ions, H + (ROH) n (n g 1), were dominantly produced by ion-molecule reactions in the liquid beam. On the other hand, H + (CH 3 ) 2 O was interpreted to be produced by unimolecular dissociation of H + (CH 3 OH) 2 in the gas phase, and its rate constant was estimated to be (5 ( 3) × 10 4 s -1 . This small rate constant suggests that the internal energy of the H + (CH 3 OH) 2 is dissipated efficiently into the liquid, so that the rate constant is much smaller than that for the same process in H + (CH 3 OH) 2 produced by ionization of a gas phase cluster. In addition, the fragment ions, H + and C + , having similar kinetic energies of ∼8 eV are considered to be produced by a multiphoton process.

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ESCA studies of phase-transfer catalysts in solution: ion pairing and surface activity

Cited by 59 publications

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Aqueous phase behaviour of choline carboxylate surfactants—exceptional variety and extent of cubic phases

Aqueous phase behaviour of choline carboxylate surfactants—exceptional variety and extent of cubic phases

Selected biologically relevant ions at the air/water interface: A comparative molecular dynamics study

Ion−Molecule Reactions in a Liquid Beam of Methanol, Ethanol, and 1-Propanol following Multiphoton Ionization

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