Effect of subphase temperature on the phase-separated structures of mixed Langmuir and Langmuir-Blodgett films of fatty acids and hybrid carboxylic acids

We examined the phase-separated structures of the mixed Langmuir-Blodgett (LB) films of C(k)H(2k+1)COOH (HkA: k=17, 21) and C(m)F(2m+1)C(10)H(20)COOH (FmH10A: m=6, 8) fabricated isothermally or after isobaric thermal treatments. Under isothermal fabrication conditions, disks and wire-type domains formed in the H17A/F6H10A LB films at high and low fabrication temperatures, respectively, because the line tension and dipole-dipole interaction were comparable with each other. The thermodynamically stable phases of H21A/F6H10A LB films at high and low fabrication temperatures were disks and polygonal domains, respectively. Isobaric thermal treatments of the Langmuir films affected the domain size and not the domain shape when the transfer temperature was the same. Isobaric thermal treatments were effective in controlling the domain size. The thermodynamically stable phases of both H17A/F8H10A LB films and H21A/F8H10A LB films were nanowires in the range of the fabrication temperatures studied. Isobaric thermal treatments of the Langmuir films did not affect the domain shape significantly and affected the domain size in both the LB films studied. The change in the value m of FmH10A was more effective in controlling the phase-separated structures of the mixed LB films than the value of k of HkA.     

Photopolymerization kinetics of monolayer and bilayer Langmuir-Blodgett films of acetylenic acid salts

The photopolymerization of thin (monolayer and bilayer) Langmuir-Blodgett films of the lead salt of 2-docosynoic acid (CH₃(CH₂)₁₈C≡CCOOH, DCA), with a triple bond near the carboxylic group, and the lead salt of 23-tetracosynoic acid (HC≡C(CH₂)₂₁COOH, TCA), with a triple bond far from the carboxyl group, has been investigated by IR spectroscopy. The principal distinctions between the polymerization kinetics of the DCA salt and that of the TCA salt are observed for bilayers. It is hypothesized that the perfection of the molecular packing in the bilayers is governed by the interlayer interaction of carboxyl groups, which exerts a stronger effect on the mutual orientation of the triple bonds in the DCA salt films as compared to the TCA salt films. A model is suggested for describing the kinetics of the two-dimensional photopolymerization of monoacetylenic compounds. A comparison between simulated and experimental data for the monolayer films demonstrates that the observed saturation of conversion (α) as a function of the UV exposure time (t) at the α ≈ 0.5?0.6 level can be attributed to the fact that the intermolecular distance lengthens with local film densification during polymerization. The effects of the substrate and the orientation of molecules in the layer on α (t) is reported.     

Calculation of the microstructure of Langmuir-Blodgett films derived from stilbazolium salts

The atom-atom potential method was used to calculate the microstructure of Langmuir-Blodgett films derived from stilbazolium salts and previously obtained experimental results were analyzed. The structure, in which the positively charged stilbazolium heads are arranged perpendicularly to the plane of the film with bromide ions between them, was found to be the most stable. The hydrocarbon tails in this packing may be displaced relative to each other such that the total thickness of the bilayer is reduced. The calculated thickness of the bilayer (48 Å) is in accord with the experimental value (49 Å). The calculated surface area of the films per molecule is 1.5 times greater than the experimental value. We propose that partial creep of the molecules relative to each other occurs upon film formation on the water surface.N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117977 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 442–444, February, 1991.     

Self-assembly of fatty acids and hydroxyl derivative salts

We report the dispersions of a fatty acid and hydroxyl derivative salts in aqueous solutions that were further used to produce foams and emulsions. The tetrabutyl-ammonium salts of palmitic acid, 12-hydroxy stearic acid, and omega-hydroxy palmitic acid formed isotropic solutions of micelles, whereas the ethanolamine salts of the same acids formed turbid birefringent lamellar solutions. The structure and dimension of those phases were confirmed by small-angle neutron scattering and NMR. Micelles exhibited a surprisingly small radius of about 20 A, even for hydroxyl fatty acids, suggesting the formation of hydrogen bonds between lipids in the core of the micelles. In the case of ethanolamine salts of palmitic and 12-hydroxy stearic acids, the lipids were arranged in bilayers, with a phase transition from gel to fluid upon heating, whereas for omega-hydroxy palmitic acid, monolayers formed in accordance with the bola shape of this lipid. Foams and emulsions produced from ethanolamine salt solutions were more stable than those obtained from tetrabutyl-ammonium salt solutions. We discuss these results in terms of counterion size, lipid molecular shape, and membrane curvature.     

Synthesis and characterization of amphiphilic fullerenes and their Langmuir-Blodgett films

We report here the synthesis and characterization of three amphiphilic fullerene derivatives and their Langmuir-Blodgett thin films. Two of the C(60) amphiphiles are mono-derivatives with a long alkyl chain terminated with either -COOH (2) or NH(2) (3) as the hydrophilic headgroup, and the third one (5) is designed to bear the same NH(2) group as 3 but with 10 additional hydrophobic alkyl chains grafted on the C(60) sphere (Scheme 1). These amphiphiles form stable, ordered monolayers at the air-water interface. The molecular packing at the air-water interface and the mean area per molecule are determined by pressure isotherms at room temperature. Hysteresis of pressure isotherms of side chain C(60) (5) shows complete reversibility upon compression and decompression, which suggests that side chains on the C(60) sphere inhibit formation of aggregates at the air-water interface. Comparative studies of all three amphiphiles allow us to better determine the interaction between C(60)'s and their self-assembly kinetics at the air-water interface. Monolayers of monoderivatized amphiphiles (2 and 3) were transferred successfully onto quartz substrates as Z-type multilayered Langmuir-Blodgett films, and monolayers of 5 were transferred as Y-type films. Detailed characterization of the multilayer films (Z-type deposition) prepared from amine-terminated C(60) (3) using X-ray and neutron reflectometry reveals staggering of C(60) spheres and a head-to-head (Y-type) structure presumably due to flipping and reattaching of C(60) amphiphiles to the previous underlying C(60) layer.     

Heavy ion induced desorption (HIID) mass spectrometry of Langmuir-Blodgett films built from CD-salts of fatty acids

Langmuir-Blodgett films made from cadmium salts of fatty acids have been analyzed by means of the heavy ion induced mass spectrometry in which megaelectronvolt ions are used to desorb sample specific molecules. The method is a useful tool for detecting incomplete salt formation at the subphase and the replacement of the original counter-ion by ions from the substrate surface. The method exhibits a depth sensitivity which can be varied between 2 to 14 layers depending on the energy loss of the heavy ion.     

Mixed films of polypeptides and fatty acids

Summary Two binary bidimensional systems both composed of an oleic acid fatty substance and a polypeptidic compound: poly--benzyl-L-glutamate, and poly--benzyl-L-aspartate have been studied.It is found that the two components are miscible with one another at the air/water interphase and give ideal solutions, as opposed to what is found with the same polypeptides in myristic and arachidic acid mixtures.

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Zusammenfassung Es werden zwei bidimensionale binäre Systeme, die aus einer fetten Substanz (Ölsäure) und aus einem Polypeptiol (Poly--benzyl-L-glutamat und Poly--benzyl-L-aspartat) zusammengesetzt sind, studiert.Es zeigt sich, daß die beiden Komponenten miteinander an der Grenzfläche H₂O — Luft mischbar sind und das sie ideale Lösungen geben, im Gegensatz zu den gleichen Polypeptiden in Mischung mit Arachinsäure oder Myristinsäure.

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With 3 figures and 1 table     

Immbolization of uricase enzyme in Langmuir and Langmuir-Blodgett films of fatty acids: possible use as a uric acid sensor

Preserving the enzyme structure in solid films is key for producing various bioelectronic devices, including biosensors, which has normally been performed with nanostructured films that allow for control of molecular architectures. In this paper, we investigate the adsorption of uricase onto Langmuir monolayers of stearic acid (SA), and their transfer to solid supports as Langmuir-Blodgett (LB) films. Structuring of the enzyme in β-sheets was preserved in the form of 1-layer LB film, which was corroborated with a higher catalytic activity than for other uricase-containing LB film architectures where the β-sheets structuring was not preserved. The optimized architecture was also used to detect uric acid within a range covering typical concentrations in the human blood. The approach presented here not only allows for an optimized catalytic activity toward uric acid but also permits one to explain why some film architectures exhibit a superior performance.     

Resorcinarene bis-crown silver complexes and their application as antibacterial Langmuir-Blodgett films

Silver complexes of a cation binding supramolecular host, resorcinarene bis-crown (CNBC5) with propyl, nonyl, decyl and undecyl alkyl chains were investigated by NMR titration, picrate extraction and single crystal X-ray diffraction. Binding studies showed that both 1 : 1 and 1 : 2 (host-Ag(+)) complexes are present in solution with only a slight effect of the lower rim alkyl chain length on the binding constants (log K 4.0-4.2 for 1 : 2 complexes). Solid state complexes of the resorcinarene bis-crowns bearing either C(3) or C(11) chains were obtained. Single crystal X-ray analyses showed that both derivatives bind silver ions by metal-arene and Ag···O coordination from the crown ether bridges and from the solvent, and pack in layered or bilayered fashion. Furthermore, the amphiphilic nature of C11BC5 was demonstrated using the Langmuir balance technique. Langmuir-Blodgett films of the amphiphilic C11BC5-Ag complex were transferred onto a substrate and shown to possess antibacterial activity against E. coli.     

Synthesis and characterization of amphiphilic phenylene ethynylene oligomers and their Langmuir-Blodgett films

We report the synthesis of a series of amphiphilic molecular building blocks that can be self-assembled at the air-water interface to form two- and three-dimensional nanostructures with tunable optoelectronic properties. Compression of these molecular building blocks using the Langmuir-Blodgett method gives rise to monolayer and multilayer thin films with different packing densities and electronic properties that are tunable due to varying pi-pi (hydrophobic) interactions. Depending on the noncovalent interaction between chromophores, we observe a transition toward denser packing with increasing number of phenylene ethynylene repeat units. Additionally, we use quantum-chemical simulations to help determine the excited-state electronic structure, intermolecular interactions, and packing trends. Our results demonstrate that the interplay between dipole-dipole and pi-pi interactions dominates the formation of thin films with various packing densities and determines the associated optical properties.     

Proton conductivity in phenolsulfonic acids and their salts

The geometric parameters and energies of crystal hydrates of aromatic sulfonic acids and their salts, as well as the pathways of proton transport in them, were calculated by the DFT (B3LYP) method with the 6-31G** basis set. For aromatic sulfonic acids, the proton relay mechanism was shown to be energetically more favorable than rotation of the HSO group or direct proton transfer. Calculations show that an increase in the number of water molecules located near the HSO₃ group from one to four decreases the barrier from 6 to 0.3 kcal/mol. Hence, a moderate increase in humidity should enhance the conductivity, which is fully consistent with experimental data. Calculations predict that the salts where all protons are substituted by metal atoms are unlikely to show good conductivity. Conversely, mixed salts, for example, H₃C₆(OH)(NaSO₃)(HSO₃) and H₃C₆(OH)(RbSO₃)(HSO₃), are expected to be thermally stable and resistant to deliquescence with an increase in the humidity of a medium and to have good conductivity.     

NO2 gas detection by Langmuir-Blodgett films of copper phthalocyanine multilayer structures

Copper (II) phthalocyanine derivatives with four alkyl chains were synthesized. Langmuir-Blodgett (LB) films of the following two compounds were deposited: Cu(II)[tetrakis(3,3-dimethyl-butoxycarbonyl)] phthalocyanine and Cu(II)[tetrakis(n-butoxycarbonyl)] phthalocyanine. Moreover, LB films from a 1:1 mixture of the two compounds were prepared. All isotherms and optical data were consistent with the molecules being stacked nearly edge-on to the substrate, with the molecular faces having a preferred orientation perpendicular to the dipping direction. The dynamic response characteristics of the electrical conductance of the LB films to different NO₂ concentrations in dry air are described. A relationship has been observed between the anisotropic molecular orientation and the electrical conductivity parallel to the substrate.     

IR and Raman spectroscopic study of the photopolymerization of Langmuir-Blodgett films of acetylenic acids

The UV induced photopolymerization of Langmuir-Blodgett films of lead salt of 2-docosynoic acid (CH₃(CH₂)₁₈C=CCOOH) is studied using IR and Raman spectroscopy. It is found that the films are a highly ordered system with trans-configuration of alkyl chains and a bridged complex generated between the carboxyl group and the lead ion. Based on a change in the absorption band intensity in the IR spectra corresponding to the triple bond vibration, the degree of polymerization depending on the irradiation time is determined. In the Raman spectra, a peak at ∼1635 cm⁻¹ appears during polymerization, which corresponds to the C=C double bond. The formation of conjugated double bonds in these systems is observed for the first time. During polymerization, methylene chains of molecules retain trans-configuration; the structural ordering of molecules in the film is observed.     

Use of atomic-atomic potentials for establishing the microstructure of Langmuir-Blodgett films of stearic acid salts

The microstructure of Langmuir-Blodgett films formed by stearic acid salts was calculated with paired atomic-atomic potentials. The calculations were performed for a monolayer and Y-type bilayer. Quantitative agreement with the experimental data was obtained in using standard values of the atomic parameters borrowed from conformational analysis. It was shown that the packing density in the films investigated is determined by the geometric dimensions of the hydrocarbon tails. In going from a monolayer to a bilayer, the geometric parameters of the two-dimensional crystal lattice remain almost unchanged, but the packing rigidity increases significantly.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2778–2782, December, 1990.     

Langmuir-Blodgett films of fluorinated glycolipids and polymerizable lipids and their phase separating behavior

This paper describes the phase separating behavior of Langmuir monolayers from mixtures of different lipids that (i) either carry already a glycopeptide recognition site or can be easily modified to carry one and (ii) polymerizable lipids. To ensure demixing during compression, we used fluorinated lipids for the biological headgroups and hydrocarbon based lipids as polymerizable lipids. As a representative for a lipid monomer, which can be polymerized in the hydrophilic headgroup, a methacrylic monomer was used. As a monomer, which can be polymerized in the hydrophobic tail, a lipid with a diacetylene unit was used (pentacosadiynoic acid, PDA). The fluorinated lipids were on the one hand a perfluorinated lipid with three chains and on the other hand a partially fluorinated lipid with a T(N)-antigen headgroup. The macroscopic phase separation was observed by Brewster angle microscopy, whereas the phase separation on the nanoscale level was observed by atomic force microscopy. It turned out that all lipid mixtures showed (at least) a partial miscibility of the hydrocarbon compounds in the fluorinated compounds. This is positive for pattern formation, as it allows the formation of small demixed 2D patterned structures during crystallization from the homogeneous phase. For miscibility especially a liquid analogue phase proved to be advantageous. As lipid 3 with three fluorinated lipid chains (very stable monolayer) is miscible with the polymerizable lipids 1 and 2, it was mostly used for further investigations. For all three lipid mixtures, a phase separation on both the micrometer and the nanometer level was observed. The size of the crystalline domains could be controlled not only by varying the surface pressure but also by varying the molar composition of the mixtures. Furthermore, we showed that the binary mixture can be stabilized via UV polymerization. After polymerization and subsequent expansion of the barriers, the locked-in polymerized structures are stable even at low surface pressures (10 mN/m), where the unpolymerized mixture did not show any segregation.     

Synthesis and structure of O-alkyl alkylphosphonoselenoic acids and their salts

Conclusions We have prepared O-alkyl alkylphosphonoselenoic acids by reaction of O-alkyl alkylphosphonites with selenium in the presence of amines or alkali metals followed by acidification. We have shown by¹H and³¹P NMR and IR spectroscopy that these acids and their salts exist in solution in the selenophosphoryl form.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya., No. 2, pp. 437–440, February, 1978.     

Polyaniline films doped with zinc salts and their properties

It has been found that thin polyaniline films doped with several zinc salts in solutions at pH 5.5 become electroconductive and electroactive in neutral aqueous electrolytes. The shape of the voltammetric characteristics depends on the initial state of the film. The effect of secondary doping withm-cresol is observed for polyaniline complexes with zinc salt of camphorsulfonic acid.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1450–1452, June, 1996.     

Bulk and surface properties of lignosulfonic acids and their salts

Results of a study of the influence exerted by the cation composition on the bulk and surface properties of modified lignosulfonates are reported. It was found that the dissolution of lignosulfonic acids is accompanied by dissociation and conformational transitions of macromolecules, which leads to concentration of molecules of lignosulfonic acids in the solution bulk and, as a consequence, to a substantial increase in the surface tension.     

Fast-atom-bombardment and tandem mass spectrometry for determining structures of fatty acids as their picolinyl ester derivatives

Picolinyl ester derivatives of common fatty acids can be readily desorbed by fast atom bombardment (FAB) as positive ions and then collisionally activated. Collisionally activated spectra of the (M + H)⁺ ions of the derivatives reveal that structurally informative remote-charge-site fragmentations occur. The presence of substitutents such as double bond, branch points, cyclopropane rings, hydroxy groups, and epoxy rings interrupts the fragmentation process in such a way that the substituent can be identified and its location on the alkyl chain can be determined. This method is also applicable to the picolinyl esters of short-chain fatty acids and to the analysis of mixtures of fatty acid derivatives. The approach is advantageous becasue the epicolinyl ester derivatives are also amenable to gas chromatography/mass spectrometry (GC/MS). Therefore, the FAB-MS/MS approach developed here is complementary to GC/MS.