Phase Transitions and Structures in Monolayers of Water Soluble and Insoluble Amphiphilic Acid Amides

Melzer, V.; Weidemann, G.; Wagner, Roland; Vollhardt, D.; DeWolf, Christine; Brezesinski, Gerald; Möhwald, H.

doi:10.1002/(sici)1521-4125(199801)21:1<44::aid-ceat44>3.0.co;2-n

Cited by 16 publications

(17 citation statements)

References 8 publications

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“…Despite the multiple presence of the amide group in biological compounds, there are only a few model studies of unsubstituted fatty acid amide monolayers. , However, systematic information was obtained about the main monolayer characteristics of various tailored amphiphiles, whose headgroup consists of an acid amide group and one or two hydroxyl groups separated by one or more methylene groups. − …”

Section: Introductionmentioning

confidence: 99%

Quantum Chemical Analysis of the Thermodynamics of 2D Cluster Formation of Aliphatic Amides at the Air/Water Interface

et al. 2012

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The semiempirical quantum chemical PM3 method is used to calculate the thermodynamic and structural parameters of formation and clusterization of aliphatic amides with the general composition C n H2n+1CONH2 (n = 6–16) at 293 and 298 K. Enthalpy, absolute entropy, and Gibbs’ energy of the formation for two stable conformations of monomers are calculated. The correlation dependencies of the calculated parameters on the alkyl chain length are found to be linear. The structures found for the monomers are used to build clusters (dimers, trimers, tetramers). The thermodynamic parameters of formation and clusterization for all cluster series are calculated. The obtained clusterzation parameters show stepwise dependencies on the alkyl chain length. It is demonstrated that the formation of two structurally different 2D films is possible. In the first film, the aliphatic amide molecules are oriented at the angles δ1 = 10° and φ1 = 20.5° to the normal to the sides of the unit cell, and in the second film, the values of these angles are δ2 = 23° and φ2 = 10°, respectively. The parameters of the unit cells of regarded monolayers are a 1 = 4.74 Ǻ, b 1 = 4.26 Ǻ, the angle between them θ1 = 89°, and a 2 = 4.51 Ǻ, b 2 = 4.74 Ǻ, θ2 = 84°, respectively. The values of θ, δ, and φ angles determine the tilt angle of alkylamide molecules with respect to the normal to the air/water interface, t 1 = 25° and ,t2 = 23°. The dependencies of the thermodynamic parameters of monolayer clusterization on the alkyl chain length of amides indicate two different types: linear for 2D film 1 and stepwise for 2D film 2. The spontaneous clusterization threshold of aliphatic amides at the air/water interface is 14 carbon atoms in the alkyl chain at 293 K for 2D film 1 and 15 carbon atoms for 2D film 2. These values agree well with the available experimental data. It is shown that the thermodynamic parameters of formation and clusterization of aliphatic amides can be obtained in the framework of the superposition–additive approach as a sum of the corresponding parameters for carboxylic acids and amines after subtraction of those alcohols.

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Section: Introductionmentioning

confidence: 99%

Quantum Chemical Analysis of the Thermodynamics of 2D Cluster Formation of Aliphatic Amides at the Air/Water Interface

et al. 2012

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“…For understanding the role of amide containing amphiphiles in inherently complex biological processes, Langmuir monolayers can be used as simple model systems. Therefore, in previous papers, the main monolayer characteristics of various tailored amphiphiles, the headgroup of which consists of an acid amide group and one or two hydroxyl groups separated by one or more (two or three) methylene groups, were studied. − The domain morphology of this type of amphiphiles is generally crystalline, despite notable differences in the domain textures.…”

Section: Introductionmentioning

confidence: 99%

Monolayer Characteristics of an N-Acylated Ethanolamine at the Air/Water Interface

et al. 2011

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The main characteristics, such as surface pressure−area (π−A) isotherms, morphology of the condensed phase domains, lattice structure of the condensed phase, and the existence of hydrogen bonds (NH···OC) of the monolayers of a highly purified N-acylated ethanolamine (C13H27CONHC2H4OH, TDAHA), are determined. At temperatures measured between 10 and 36 °C, the characteristics of the surface pressure−area (π−A) isotherms, which indicate the main first-order phase transition from the fluid phase to the condensed phase, are similar to those of usual amphiphiles. However, at temperatures of ≤10 °C, a second inflection point whose transition pressure increases strongly with increasing temperature proves the existence of a second first-order phase transition between two condensed phases. The entropy change of this second transition is small with only 10% of that observed for the main phase transitions at the same temperature. The fractal-like shaped condensed phase domains have a limited tendency to branching and are characterized by the absence of an inner texture in the homogeneously reflecting domains. The characteristic features of the two-dimensional lattice structure are obtained by GIXD studies. An oblique lattice is formed after the main phase transition with a cross-sectional area of 19.3 Å2, whereas after the second phase transition an orthorhombic L2′ phase arises accompanied by a drastic decrease of the molecular tilt angle. The IRRAS experiments confirm the existence of an extended hydrogen bonding network (NH···OC) in the TDAHA monolayers by the positions of the amide bands and the transition from an oblique into an orthorhombic phase by the split of the CH2 deformation band.

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“…Despite the numerous papers concerning synthesis, occurrence, and application of derivatives of amino alcohols with long-chain fatty acids, there is only little information on the interfacial characteristics of some selected amphiphiles of this type. In fact, we investigated the main monolayer characteristics of various tailored amphiphiles containing an amide group and one or two hydroxyl groups separated by one or more (two or three) methylene groups, − but with N -myristoylethanolamine (C 13 H 27 − CO − NH −C 2 H 4 OH) only one N-acylated ethanolamine has been studied . However, information about monolayer characteristics of long-chain N,O-diacyl compounds of ethanolamine is completely missing.…”

Section: Introductionmentioning

confidence: 99%

Monolayer Characteristics of a Long-Chain N,O-Diacyl Substituted Ethanolamine at the Air/Water Interface

et al. 2011

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The N- and/or O-acylation of amphiphilic ethanolamine attracts particular attention because of its interesting biological, pharmaceutical, and medicinal properties. Tetradecanoic acid-2-[(1-oxotetradecyl)amino]ethyl ester (TAOAE) as the selected N,O-diacyl derivative of ethanolamine has been synthesized in order to obtain first information about its main interfacial characteristics, such as the surface pressure−area (π−A) isotherms, the morphology of the condensed phase domains, the lattice structure of the condensed phase, and information about the existence of interfacial hydrogen bonds (−NH···OC−). The π−A isotherms of TAOAE, similar to those of the most usual monolayers of amphiphiles, show a sharp break point (A c) indicating the first-order phase transition from the fluid (liquid-expanded (LE), gaseous (G)) to the condensed (liquid-condensed (LC)) phase. On the mesoscopic scale, the dendritic domains homogeneously reflecting suggest an orientation of the alkyl chains perpendicular to the aqueous surface. The grazing incidence X-ray diffraction (GIXD) studies reveal hexagonal packing of the TAOAE molecules oriented perpendicular to the surface in an LS phase. The existence of a hydrogen-bonding network in the monolayer is supported by infrared reflection absorption spectroscopy (IRRAS) experiments.

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Phase Transitions and Structures in Monolayers of Water Soluble and Insoluble Amphiphilic Acid Amides

Cited by 16 publications

References 8 publications

Quantum Chemical Analysis of the Thermodynamics of 2D Cluster Formation of Aliphatic Amides at the Air/Water Interface

Quantum Chemical Analysis of the Thermodynamics of 2D Cluster Formation of Aliphatic Amides at the Air/Water Interface

Monolayer Characteristics of an N-Acylated Ethanolamine at the Air/Water Interface

Monolayer Characteristics of a Long-Chain N,O-Diacyl Substituted Ethanolamine at the Air/Water Interface

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