Amphiphilic Amide Research Articles

Experimental investigation on hydrate anti-agglomerant for oil-free systems in the production pipe of marine natural gas hydrates

During the production of marine natural gas hydrates, as gas hydrates are easily formed, they tend to agglomerate, deposit on the pipe walls, and eventually block the pipe. In this study, high-pressure autoclave and micromechanical force apparatus were used to investigate the effects of anti-agglomerants and kinetic inhibitors on the hydrate agglomeration in the oil-free gas–water system, and the anti-agglomeration mechanism was analyzed. The results indicate that when the hydrate conversion rate reached about 27%, a complete blockage occurred. In the oil-free system, conventional anti-agglomerants did not exhibit any anti-agglomeration performance; while kinetic inhibitors slowed down the hydrate formation, but could not inhibit their agglomeration. An amphiphilic amide compound, namely DCA, effectively prevented hydrate agglomeration and blockage under the simulated hydrate production conditions of 8-h stirring and subsequent 8-h shut-in. From the perspective of interparticle interaction, 1.0 wt% DCA reduced the cohesion force between cyclopentane hydrate particles by 62% and 70% in liquid cyclopentane and air, respectively. These effects were attributed to the adsorption of DCA on the surface of hydrate particles, which converted the surface characteristic from hydrophilic to hydrophobic; thus, no liquid bridge could be formed between particles. Moreover, DCA formed an isolating layer and offered steric hindrance, thus preventing the adhesion and agglomeration of hydrates.

Amide-Linked Dendron-based Amphiphiles: A class of pH sensitive and highly biocompatible drug carrier for sustained drug release

ABSTRACT PG-dendritic amide-linked amphiphilic micelles were studied to increase the solubility of hydrophobic molecules. The encapsulation study was done by utilising hydrophobic pyrene dye using U.V. technique. The encapsulation efficiency of the non-ionic amphiphiles was obtained at neutral p.H. and at room temperature (p.H. 7.0 & 28 °C). The G.3 dendron-based non-ionic oleic (C18-cis)-amphiphile was found to have the 78.2% encapsulation efficiency. Studies show that the amide-linked G.1 dendron-based non-ionic (C18-cis) amphiphiles have sustained dye release percentage of 78.00% at p.H. 6.2 and 26.19% at p.H. 7.0 in 72 h at 37 °C. The in vitro cyto-toxicological studies showed that after 24–48 h treatment, the G.1 amide amphiphiles exhibit more than 80% of cell viability for concentration as high as 31.25 μg/mL. The cellular uptake was demonstrated using Coumarin 6. The integrated amphiphiles are biocompatible and can be used in the biomedical field as medication encapsulation and target drug delivery.

Structure and stretching dynamics of water molecules around an amphiphilic amide from FPMD simulations: A case study of N,N-dimethylformamide

N,N-Dimethylformamide (DMF) is a unique tertiary amphiphilic amide, where the presence of a hydrophilic aldehyde group favors hydrogen bond acceptance, but two hydrophobic methyl substituents inhibit interaction with water molecules. As a result, the water molecules encounter two different environments in the vicinity of DMF molecule: around the hydrophobic nitrogen site; and near the hydrophilic carbonyl oxygen. We employ first principles molecular dynamics methods to simulate an aqueous solution of DMF using PBE functional with Grimme's D3 dispersion correction at 330 K. Investigations on the liquid structure to understand inter-atomic interactions in amides attract much attention. We calculated various structural and dynamical properties along with vibrational stretching frequency of water molecules to understand heterogeneously affected water molecules by an amphiphilic amide molecule. In solvated DMF, the first peak minimum of the N-OW and OC-OW radial distribution functions (‘w’ subscript denotes atoms of water) are located at 5.72 and 3.16 Å, respectively. These distance cutoffs decide the boundary of the solvation shell. At OC-HW distance 2.45 Å, the deep peak minimum indicates stable OC … HW hydrogen bond. Previous Monte Carlo simulations reported the presence of hydrogen bonds between the oxygen site of DMF and hydrogen of water. The time-series wavelet method was used to compute the time-dependent frequencies of the hydroxyl groups of water. The average frequency of the OH modes inside the CO solvation shell (~3364 cm−1) in DMF is higher than bulk (~3337 cm−1), and the trend matches with an aqueous solution of acetone. In nitrogen hydration shell, the intense band resembles the bulk frequency distribution, and a narrow distinctive peak at the high-frequency side (range ~3650–3750 cm−1) represents the non‑hydrogen bonded or dangling OH groups. Raman spectroscopy in hydrophobic TBA and air/water interface displayed dangling OH stretch peak at ~3660 cm−1 and ~3710 cm−1, respectively. Our calculation of the frequency distribution, frequency-frequency correlation function, and hydrogen bond dynamics show the water molecules at bulk behave as in pure water. Inside the solvation shell of aminic nitrogen, non‑hydrogen bonded OH modes with a dangling lifetime ~0.38 ps dominates over the water-water hydrogen bonds. The time-dependent decay of the frequency correlation inside CO solvation shell has three decay components, a rapid decay, then, an intermediate component (~1.52 ps) corresponding to the lifetime of the carbonyl-water hydrogen bond, and the longer timescale ~11.97 ps representing the residence time of water molecules in the vicinity of carbonyl oxygen. We find that the carbonyl-water hydrogen bond (OC … HW) is stronger than the water-water hydrogen bond. The methyl substituents on the nitrogen of DMF impose weak hydrophobic interaction, and the hydrophilic carbonyl oxygen forms a strong hydrogen bond with the neighboring water resulting in localized dynamics.

Chiral nanostructures self-assembled from nitrocinnamic amide amphiphiles: substituent and solvent effects.

Chiral nanostructures, such as α-helical proteins and double helix DNA, are widely found in biological systems and play a significant role in the biofunction of life. These structures are essentially fabricated through the covalent or noncovalent bonds between small chiral molecules. It is thus an important issue to understand how small chiral molecules can form chiral nanostructures. Here, using a series of isomeric nitrocinnamic amide derivatives, we have investigated the self-assembly behavior and the effect of the substituent position as well as the solvent on the formation of chiral nanostructures. It was found that totally different chiral nanostructures were formed due to the different positions of the nitro group on the cinnamic amide. Moreover, it was found that the chiral sense of the self-assembled nanostructures can be regulated by the solvent whereby helicity inversion was observed. This work provides a simple way to regulate the self-assembly pathway via molecular design and choice of solvent for the controlled creation of chiral nanostructures.

Aminolysis of linoleic and salicylic acid derivatives with Candida antarctica lipase B: A solvent-free process to obtain amphiphilic amides for cosmetic application

In this biotechnological process, the fatty amides (9Z,12Z)-N-dodecyloctadeca-9,12-dienamide (3) and N-dodecyl-2-hydroxybenzamide (5), respectively derived from linoleic acid and salicylic acid were synthesized through aminolysis reactions catalyzed by Candida antarctica lipase B. These amphiphilic compounds receive great attention from cosmetic industry due to a range of beneficial properties for skin. The aminolysis reactions were performed with the esters ethyl linoleate (1) and ethyl salicylate (4) as acyl group donors and the fatty compound N-dodecylamine (2) as the nucleophilic substrate. The aminolysis reactions were carried out in a solvent-free process, which is beneficial from an environmental and economical perspective, at 65°C and reduced pressure (50mbar). Parameters as enzyme amount and substrates molar ratios were investigated and the products were monitored by HPLC analysis. The conversion rates were measured through disappearance of ethyl linoleate and ethyl salicylate. The best conversion rates (up to 95%) were obtained by adding an enzyme amount of 5.0g/mol of acyl donor group substrate and an equimolar substrates ratio (1:1). The products characterization was performed by High Resolution Mass Spectrometry, Infrared spectroscopy and Nuclear Magnetic Ressonance. This work reveals that enzymatic synthesis provides an attractive way for the cosmetic industrial production of fatty amides, which may represent key ingredients to maintain and/or restore a healthy skin.

Synthesis and Antibacterial Activity of Alkylated Diamines and Amphiphilic Amides of Quinic Acid Derivatives.

Different series of N-alkylated diamines and their derivatives condensed to quinic acid were synthesized and tested for antibacterial properties against Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Mycobacterium tuberculosis. The lipophilic chain and carbohydrate moiety modulate the antibacterial activity and the compounds showed a structure-activity relationship. Overall, 11 compounds displayed better activity than chloramphenicol against Gram-positive and Gram-negative bacteria. Monoalkylated amines 2a-h displayed an activity similar to that of ethambutol against Mycobacterium tuberculosis.

Comparison of the gelation behaviour of N-substituted tetradecanamide amphiphiles in organic liquids: effect of hydrogen-bonding ability of the head-group

In this work, we have investigated the role of intermolecular hydrogen-bonding (H-bonding) interaction of the head-groups of amphiphilic organogelators. For this we have designed, synthesized and studied the gelation behaviour of a series of amide amphiphiles having hydrocarbon chains with the same length (C14) but with –COOH, –OH, –NH2 or –N(CH3)2) functionalities as head-group. These gelators, except the one with –N(CH3)2 head-group, efficiently gelated aromatic solvents. The gelation in all the solvents employed was observed to be thermoreversible. The gels were characterized by XRD spectroscopy, electron microscopy, and rheology. The amphiphiles were observed to form ribbon-like aggregates in aromatic solvents. The gel-to-sol transition temperatures as well as mechanical strengths of the organogels were observed to increase with the spacer length. The results suggest that the intermolecular H-bonding interactions between head-groups were essential for gelation.

Two-Dimensional Miscibility Behavior of Two Chemically Similar Amide Amphiphiles

The monolayer characteristics of two chemically similar amphiphiles 3-hydroxy-N-tridecyl propanoic acid amide (HTPA) and tetradecanoic acid-(2-hydroxyethyl)amide (TDAHA) and their selected mixtures are studied. Despite the slight structural difference (the position of the two substituents at the acid amide group), the pure components reveal large differences and peculiarities in the surface pressure–area (π-A) isotherms, the monolayer morphologies, and structures. Therefore, their miscibility behavior in monolayers is of special interest. At low temperatures (T ≤ 10 °C), the π-A isotherms of the pure components show a striking second critical point accompanied by an abrupt change of important 2D lattice parameters, indicating the existence of a second phase transition between two condensed phases. This second phase transition is strongly temperature-dependent for TDAHA, nearly temperature-independent for HTPA, and not occurring in the investigated mixtures. The results of Brewster angle microscopy and grazing incidence X-ray diffraction support ideal miscibility of HTPA-TDAHA monolayers already suggested by the linear relationship between the main phase transition pressure and the mole fraction. The lattice parameters of the mixed TDAHA-HTPA monolayers measured for three mole fractions (0.25, 0.5, and 0.75) at 5 °C are compared and discussed. The tilt angle in the mixed TDAHA-HTPA monolayers passes through a minimum, which is connected to the largest cross-sectional area and the smallest entropy change during the main LE/LC (liquid expanded/liquid condensed) transition. An HTPA-TDAHA phase diagram that illustrates the transitions between the different phases is proposed.

Dominance of long-chain N,O-diacylated ethanolamine in mixed amphiphilic acid amide monolayers

The main characteristics of Langmuir monolayers of acid amide amphiphiles with one and two alkyl chains are fundamentally different. This is demonstrated by comparison of surface pressure–area ( π– A) isotherms, the mesoscopic morphology, and the two-dimensional lattice structure of the condensed phases in the case of the single-chain acid amides with N-myristoyl ethanolamine (TDAHA) and 3-hydroxy-N-tridecyl propanoic acid amide (HTPA) as well as in the case of the double-chain acid amide with N,O-dimyristoyl ethanolamine (TAOAE). The studies of the binary mixtures TDAHA/TAOAE, HTPA/TDAHA, HTPA/TAOAE (1:1) and ternary mixtures TAOAE/TDAHA/HTPA (1:1:1) performed at 5 °C and 25 °C allow the comparison with the single components. The results indicate convincingly that all binary 1:1 monolayers and the ternary 1:1:1 monolayer exist as homogeneously mixed systems. The dominance of the double-chain TAOAE in the binary and ternary monolayers mixed with single-chain acid amide amphiphiles TDAHA and HTPA in mesoscopic and molecular scale can be unequivocally concluded from the GIXD and BAM measurements. The probability for the presence of N,O-diacylated ethanolamine, such as TAOAE, as impurity in N-acylated ethanolamine, e.g. TDAHA, is high so that in such systems the most important interfacial characteristics are dominated by the impurity.

Self‐Assembly of Vesicles by a 2,6‐Di(7‐benzamidy)quinolin‐2‐ yl)pyridine Derivative Tuned by an Amphiphilic Amide Chain

AbstractThis paper describes 2‐(2‐(dioctylamino)‐2‐oxoethyl‐amino)‐2‐oxoethoxyl (DOAOE)‐tuned self‐assembly of vesicles from a 2,6‐di(7‐benzamidy)‐quinolin‐2‐yl)pyridine derivative. Scanning electron (SEM), transmission electron (TEM) and optical microscopy and dynamic light scattering (DLS) studies reveal that the molecule self‐assembles into vesicular structures in methanol. The influence of the transition metal ions and trifluoroacetic acid on the formation of the vesicles was investigated. The results illustrate that DOAOE is robust in promoting the formation of vesicles for aromatic systems in polar medium.

Cross-Sectional Area Increase at Phase Transition on Compression: An Unexpected Phenomenon Observed in an Amide Monolayer

At low temperatures (T ≤ 10 °C), the surface pressure−area (π−A) isotherms of some amphiphilic amides reveal a striking second critical point indicating the existence of a second phase transition between two condensed phases. Studies of 3-hydroxy-N-tridecyl propanoic acid amide (HTPA) monolayers have shown that this phase transition between two condensed phases is accompanied by an abrupt change of important 2D lattice parameters. Thorough grazing incidence X-ray diffraction (GIXD) studies have revealed a new phenomenon. The cross-sectional area (A0) of the alkyl chain of HTPA jumps from a smaller value in the phase at the lower surface pressure to a larger value in the phase existing at higher pressure. The opposite behavior should be expected and is usually noted in the lattice structures of Langmuir monolayers. The phase diagram of the HTPA monolayers is constructed on the basis of the equilibrium π−A isotherms. The fact that two condensed monolayer phases exist and the phase observed above the fluid/c...

ChemInform Abstract: Synthesis and Evaluation of the Properties of Fluorinated Amphiphilic Amides of 2,2-Bis(hydroxymethyl)propionic Acid.

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Amphiphilic Amide Nitrones: A New Class of Protective Agents Acting as Modifiers of Mitochondrial Metabolism

Our group has demonstrated that the amphiphilic character of alpha-phenyl-N-tert-butyl nitrone based agents is a key feature in determining their bioactivity and protection against oxidative toxicity. In this work, we report the synthesis of a new class of amphiphilic amide nitrones. Their hydroxyl radical scavenging activity and radical reducing potency were shown using ABTS competition and ABTS(+) reduction assays, respectively. Cyclic voltammetry was used to investigate their redox behavior, and the effects of the substitution of the PBN on the charge density of the nitronyl atoms, the electron affinity, and the ionization potential were computationally rationalized. The protective effects of amphiphilic amide nitrones in cell cultures exposed to oxidotoxins greatly exceeded those exerted by the parent compound PBN. They decreased electron and proton leakage as well as hydrogen peroxide formation in isolated rat brain mitochondria at nanomolar concentration. They also significantly enhanced mitochondrial membrane potential. Finally, dopamine-induced inhibition of complex I activity was antagonized by pretreatment with these agents. These findings indicate that amphiphilic amide nitrones are much more than just radical scavenging antioxidants but may act as a new class of bioenergetic agents directly on mitochondrial electron and proton transport.

Highly Symmetric 2D Rhombic Nanoporous Networks Arising from Low Symmetry Amphiphiles

Highly symmetric 2D nanoporous molecular networks containing rhombic voids are demonstrated to be accessible from low symmetry amphiphilic molecules. The amide amphiphiles overcome the barrier to symmetry generation in the two-dimensional crystal through forming an aggregate as a building block. This aggregate consists of three inequivalent amphiphiles that assemble to create 3- and 6-fold rotation axes through hydrogen bonding. In the 6-fold rotation axis, an unusual hydrogen bonding network, supported by high resolution scanning tunneling microscopy (STM) images and computation, is observed. This network formed by amide groups significantly contributes to constructing the rhombic nanoporous network, whereas carboxylic acid amphiphiles do not adopt this nanoporous network due to a geometric difference of hydrogen bonding. This investigation demonstrates that a high symmetry pattern is achievable without correlation with molecular symmetry through the proper combination of noncovalent interactions of simple amphiphilic molecules.

Thermodynamic Characterization of Mixed Monolayers of Two Similar Amide Amphiphiles Different Only by Exchange of Substituents Position

The monolayer features of two very similar amphiphiles, N-tridecyl-beta-hydroxypropionic acid amide (THPA) and N-(beta-hydroxyethyl) tridecanoic acid amide (HETA) and their 1:1 mixture are studied. The behavior of the mixed monolayer is of special interest as already the pure components reveal large differences of the surface pressure-area (pi-A) isotherms, in particular, because of the second phase transition between two condensed phases at low temperatures in the THPA monolayer. This second phase transition occurs in the mixed monolayer, as well. The thermodynamic characteristics of the mixed HETA/THPA monolayers are compared with those of the pure components. The thermodynamic analysis is performed on the basis of the equations of state for the monolayer in the fluid (G, LE)/condensed (LC) transition region (A<Ac) with bimodal distribution (large clusters and monomers) and in the fluid (G, LE) state (A>or=Ac) considering the contribution of the entropy nonideality, caused by the mixing of monomers and clusters. Good agreement between the experimental pi- A isotherms and the theoretical results are obtained. The results of the thermodynamic analysis allow conclusions on the specific phase properties of the mixed HETA/THPA monolayers. Finally the additive model applied for the theoretical description at higher temperatures provides good agreement with the experimental results at temperatures of >or=20 degrees C.

Artificial photosynthesis based on dye-sensitized nanocrystalline TiO 2 solar cells

A new series of amphiphilic heteroleptic ruthenium(II) sensitizers [Ru(H 2dcbpy)(dhbpy)(NCS) 2] ( C1), [Ru(H 2dcbpy)(bccbpy)(NCS) 2] ( C2), [Ru(H 2dcbpy)(mpubpy)(NCS) 2] ( C3), [Ru(H 2dcbpy)(bhcbpy)(NCS) 2] ( C4) have been synthesized and fully characterized by UV–Vis, emission, NMR and cyclic voltammetric studies (where dhbpy = 4,4′-dihexyl-2,2′-bipyridine, bccbpy = 4,4′-bis(cholesteroxycarbonyl)-2,2′-bipyridine, mpubpy = 4-methyl-4′-perfluoro-1 H,1 H,2 H,2 H,3 H,3 H-undecyl-2,2′-bipyridine, bhcbpy = 4,4′-Bis(hexylcarboxamido)-2,2′-bipyridine). The amphiphilic amide heteroleptic ruthenium(II) sensitizers, self-assembled on TiO 2 surface from ethanol solution, reveal efficient sensitization in the visible window range yielding ≈80% incident photon-to-current efficiencies (IPCE). Under standard AM 1.5 sunlight, the C4 sensitizer gave 15 mA/cm 2 short circuit photocurrent density, 0.66 fill factor and an open circuit voltage of 0.75 V, corresponding to an overall conversion efficiency of 7.4%.

Amphiphilic Amide Derivatives of D‐Glucaric Acid. Synthesis and Complexing Properties Toward Lanthanide(III) Ions

AbstractHydrophobic derivatives of D‐glucaric acid, HOOC−(CHOH)4−CONHR,where R is an alkyl chain having 3, 8, 10, or 12 carbon atoms, have been synthesized from D‐glucaro‐1,4‐lactone and the corresponding amines. The complexing abilities of these compounds toward trivalent lanthanide cations have been studied, using the water‐soluble propyl compound, and compared to that of gulonic acid, which corresponds to the complexing part of these molecules. The formation constants of the complexes have been determined and their structures discussed. The surfactant properties of the C8, C10 and C12 glucaramides and their extracting ability toward LnIII ions have also been evaluated. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2004)

Molecular engineering on semiconductor surfaces: design, synthesis and application of new efficient amphiphilic ruthenium photosensitizers for nanocrystalline TiO 2 solar cells

A new series of amphiphilic heteroleptic ruthenium(II) sensitizers [Ru(H 2dcbpy)(dhbpy)(NCS) 2] ( C1), [Ru(H 2dcbpy)(dchobpy)(NCS) 2] ( C2), [Ru(H 2dcbpy)(mubpy)(NCS) 2] ( C3), [Ru(H 2dcbpy)(dhabpy)(NCS) 2] ( C4) have been developed and fully characterized by UV-visible, emission, NMR and cyclic voltammetric studies (where mubpy=4-methyl-4′-perfluoro 1H, 1H, 2H, 2H, 3H, 3H undecyl-2,2′-bipyridine, dhabpy=4-4′-dihexylamide-2,2′-bipyridine, dhbpy=4-4′-dihexyl-2,2′-bipyridine, dchobpy=4-4′-dicholesteryl-2,2′-bipyridine). The amphiphilic amide heteroleptic ruthenium(II) sensitizers, when anchored to nanocrystalline TiO 2 films from ethanol solutions, achieve very efficient sensitization in the visible range yielding ≈80% incident photon-to-current conversion efficiency (IPCE) and display a short circuit photocurrent density of 15 mA/cm 2 and an open circuit voltage of 0.75 V corresponding to an overall conversion efficiency of 7.4% under standard AM 1.5 sunlight.

Reorganization of Langmuir monolayers on solid surfaces

Abstract Langmuir–Blodgett (LB) monolayers of behenic acid, beeswax and long-chain amphiphilic amides were prepared on graphite and mica surfaces by the horizontal precipitation method. The monolayer films and products of their reorganization were studied with atomic force microscopy. LB films of amphiphilic amides were found to self-organize into superstructures with a hexagonal arrangement of hydrocarbon tails. Repeatedly observed supramolecular formations suggest that reorganization is a common phenomenon in monolayers on substrates. It is suggested that the driving force for the molecular reorganization is the surface tension gradient arising from the change in type of hydrocarbon tails packing.

Theory of Self-Assembled Tubules and Helical Ribbons

Many types of amphiphilic molecules self-assemble in solution to form cylindrical tubules and helical ribbons. Some examples include diacetylenic lipids, amide amphiphiles, bile, and diblock copolymers. Researchers have proposed a variety of models to explain the formation of these high-curvature structures. These models can be divided into two broad categories: models based on the chiral elastic properties of membranes, and models based on other effects, including electrostatic interactions, elasticity of orientational order, and spontaneous curvature. In this paper, we review the range of theoretical approaches and compare them with relevant experiments. We argue that the category of models based on chiral elastic properties provides the most likely explanation of current experimental results, and we propose further theoretical and experimental research to give a more detailed test of these models.