Phase Transition in Langmuir Films of Octadecylmalonic Acid

Collins, Scott; Dhathathreyan, A.; Ramasami, T.

doi:10.1006/jcis.1998.5504

Cited by 11 publications

(6 citation statements)

References 39 publications

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“…In recent years, molecular dynamics (MD) simulations also have been widely used to investigate the molecular structures of surfactants at various interfaces or in aqueous solution [31][32][33][34][35]. Some structures and molecular orientations at the air/liquid interface predicted by these methods are in good agreement with many experimental observations [36,37].…”

Section: Introductionmentioning

confidence: 67%

Surface behavior of a model surfactant: A theoretical simulation study

Yuan¹,

Yan²,

Lv³

et al. 2010

Journal of Colloid and Interface Science

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Section: Introductionmentioning

confidence: 67%

Surface behavior of a model surfactant: A theoretical simulation study

Yuan¹,

Yan²,

Lv³

et al. 2010

Journal of Colloid and Interface Science

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“…Initial research was focused on their different behavior on the water surface depending on the position of the polar groups in the molecule. Aliphatic molecules having either identical (alkyl diols, dicarboxylic acids, , diammonium halides, aromatic amines) or different polar groups (like hydroxycarboxylic acids − ) have been studied most frequently. For both kinds of bipolar molecules, the same monolayer behavior was observed.…”

Section: Introductionmentioning

confidence: 99%

“…For both kinds of bipolar molecules, the same monolayer behavior was observed. Namely, when polar groups were placed in an adjacent position, they were acting as a common entity and the characteristics of their Langmuir monolayers resembled those for monopolar amphiphiles. − The high monolayer stability has suggested that they are anchored with both polar groups in the water surface and their orientation does not change with the compression . However, when polar groups were located further away so that a headgroup is present on each end of a hydrophobic skeleton, like for α,ω-bipolar compounds (ref and references therein ,,− ) (referred to as “bolaamphimphiles”, “bolas”, “bolytes”, or “bolaform amphiphiles”), such molecules were found to behave differently.…”

Section: Introductionmentioning

confidence: 99%

Unusual Behavior of the Bipolar Molecule 25-Hydroxycholesterol at the Air/Water Interface—Langmuir Monolayer Approach Complemented with Theoretical Calculations

et al. 2020

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In this study, 25-hydroxycholesterol (25-OH), a biamphiphilic compound with a wide range of biological activities, has been investigated at the air/water interface. We were interested in how two hydroxyl groups attached at distal positions of the 25-OH molecule (namely, at C(3) in the sterane system and at C(25) in the side chain) influence its surface behavior. Apart from traditional Langmuir monolayers, other complementary surface-sensitive techniques, such as electric surface potential measurements, Brewster angle microscopy (BAM, enabling texture visualization and film thickness measurements), and polarization modulation-infrared reflection-absorption spectroscopy (PM-IRRAS), were applied. Experimental data have been interpreted with the aid of theoretical study. Our results show that 25-OH molecules in the monomolecular layer are anchored to the water surface alternatively with C(3) or C(25) hydroxyl groups. Theoretical calculations revealed that the populations of these alternative orientations were not equal and molecules anchored with C(3) hydroxyl groups were found to be in excess. As a consequence of such an arrangement, surface films of 25-OH are of lower stability as compared to cholesterol (considered as a non-oxidized analogue of 25-OH). Moreover, it was found that, upon compression, the transition from mono- to bilayer occurred. The molecular mechanism and interactions stabilizing bilayer structure were proposed. The explanation of the observed unusual surface behavior of 25-OH may contribute to an understanding of differences in biological activity between chain- and ring-oxidized sterols.

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“…This was done for sodium dodecylsulfate,23 hexadecyltrimethylammonium chloride/bromide,24h25 phenol and p-n-pentylphenol, N,N@diethyl-p-nitroaniline,26,27,29 hexanol/water mixtures28 and octadecylmalonic acid. 31 In 32,33 In these works we used 25 surfactant molecules32 respectively 36 surfactants33 adsorbed at the water surface with a surface concentration of 0.55 nm2 molecule~1. From our studies we obtained an average tilt angle of the dodecyl chains of about 43¡ measured in respect to the surface normal vector.…”

Section: Introductionmentioning

confidence: 99%

Molecular orientation of monododecyl pentaethylene glycol (C12E5) surfactants at infinite dilution at the air/water interface. A molecular dynamics computer simulation study

Kühn

Rehage

2000

Phys. Chem. Chem. Phys.

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In this publication we used a molecular dynamics computer simulation in order to get more detailed insights into the adsorption process of monododecyl pentaethylene glycol surfactants. We investigated the (C 12 E 5 ) surface between water and air at inÐnite small surfactant concentrations. Measured in respect to the surface normal vector the average tilt angle of the chain was found to be of the order of 67.4¡ ^18.3¡. For the C 12 polar pentaethylene glycol chains we observed tilt angles of 78.0¡ ^8.5¡. These results indicate that the molecules are lying nearly Ñat on the water surface. This observation is in fairly good agreement with neutron reÑection experiments of and also with a previously performed simulation of sodium dodecylsulfate. C 12 E 3 Additionally, it turned out that the conformations of surfactant molecules adsorbed at the air/water C 12 E 5 interface are similar to the molecular arrangements of in the vacuum phase. This holds, at least, for the C 12 E 5 regime of inÐnitely small surfactant concentrations.

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Phase Transition in Langmuir Films of Octadecylmalonic Acid

Cited by 11 publications

References 39 publications

Surface behavior of a model surfactant: A theoretical simulation study

Surface behavior of a model surfactant: A theoretical simulation study

Unusual Behavior of the Bipolar Molecule 25-Hydroxycholesterol at the Air/Water Interface—Langmuir Monolayer Approach Complemented with Theoretical Calculations

Molecular orientation of monododecyl pentaethylene glycol (C12E5) surfactants at infinite dilution at the air/water interface. A molecular dynamics computer simulation study

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