Investigation of the optimization of the recovery of mineral oil from water

A method has been derived to completely recover mineral oil dispersed in water. The method involves three steps: the emulsification of the mineral oil by adding amphiphiles, the breaking of the emulsion by adding salts and the extraction of the mineral oil by a non-polar aprotic solvent. Various amphiphiles and types and concentrations of salts were tested. By using amphiphiles with HLB numbers in the range 4.7 to 40 a complete recovery of the mineral oil could be obtained for a combination of salts Na₂SO₄ + NaH₂PO₄ with total ionic strength of 6 mol/L. Received: 30 September 1998 / Revised: 8 March 1999 / Accepted: 10 March 1999     

Aqueous phase behavior of polyelectrolytes with amphiphilic counterions modulated by cyclodextrin: the role of polyion flexibility

Polyelectrolytes with amphiphilic counterions, PEACs, are water insoluble because the amphiphiles self-assemble into highly charged micelles that strongly associate with the equally highly charged polyions. However, in the presence of water soluble cyclodextrins (CDs) that form inclusion complexes with the amphiphiles and prevent micellization, PEACs become soluble as the dispersed amphiphiles behave essentially as simple monovalent counterions. In this paper, we illustrate, by example, how strongly the ternary phase behavior of PEAC:CD:water depends on the polyion flexibility; for a highly flexible polyion (polyacrylate) the amphiphilic aggregates dictate the phase behavior, whereas a much stiffer polyion (DNA) itself dictates liquid crystalline ordering.     

Synthesis and aqueous aggregation properties of amphiphilic surface-block dendrimers

[reaction: see text] A family of dendritic amphiphiles were synthesized from the natural metabolites of glycerol, succinic acid, and myristic acid. The surfaces of these dendrimers display different numbers of alkyl chains and carboxylic acids, varying the hydrophobic-to-hydrophilic ratio over a relatively broad range. In solution these dendritic amphiphiles form supramolecular structures, and these aggregates have been characterized by light microscopy, transmission electron microscopy, and tensiometry. These aggregates can entrap the hydrophobic species pyrene.     

Effects of Helical Sense and Macrodipole on Helix Interaction in Poly(glutamic acid) Monolayers at the Air-Water Interface

The effect of the helical sense and the helical macrodipole moment of poly(glutamic acid) (PGA) amphiphiles on miscibility in their binary surface monolayers was examined by means of the surface pressure-area isotherm and spectroscopic measurements. Four types of PGA amphiphiles, having different chirality (l or d) and two long alkyl chains at the C- or N-terminus (1 or 2), were successfully prepared by polymerization of the corresponding NCAs. In acidic solutions, these amphiphiles were found to take right-handed or left-handed helical conformation, depending upon the chirality of the glutamic acid unit, and are dispersed in water molecularly without aggregation. On the other hand, the binary mixed monolayer of 1L and 1D provided a marked positive deviation from an ideal mixing curve, while that of the combination of 1L and 2L gave a much smaller negative deviation, suggesting that helical sense would play a more important role in monolayer miscibility. Copyright 1999 Academic Press.     

Investigation in monolayers of double-chain fluorocarbon amphiphiles Effect of headgroups on molecular packing and interaction between hydrocarbon and fluorocarbon monolayers

The surface pressure-area diagrams of double-chain fluorocarbon amphiphiles with different headgroup compositions show that the amphiphiles arrange almost perpendicularly to the water subphase and the structure of headgroups exerts significant influence on the amphiphile packing. Strong hydrogen bonding and weak electrostatic interaction favor the formation of stable monolayers. Perfluorooctanoic acid (FOA) cannot form monolayer at water/air interface and can only form liquid monolayer in subphase of calcium nitrate solution. Complete phase separation of palmitic acid and a fluorocarbon amphiphile with shorter hydrocarbon spacer group, 1, could be demonstrated in monolayers by using the phase rule of Crisp. The creation of phase-separated monolayers is possible when the monolayer is composed of a mixture of palmitic acid and a fluorocarbon amphiphile with longer hydrocarbon spacer group, 2. It can be suggested that the miscibility of hydrocarbon amphiphiles with fluorocarbon amphiphiles is determined by the hydrocarbon fraction of fluorocarbon amphiphiles.     

Regulation of aggregation and morphology of cyanine dyes on monolayers via gemini amphiphiles

The aggregation of dyes is of considerable importance in relating to their functions and applications. In this paper, we have investigated the regulation on the aggregation and morphology of two cyanine dyes, 3,3'-disulfopropyl-4,5,4',5'-dibenzo-9-methylthiacarbocyanine triethylammonium salt (MTC) and 3,3'-disulfopropyl-4,5,4',5'-dibenzo-9-phenylthiacarbocyanine triethylammonium salt (PTC), using a series of gemini amphiphiles (bis(2'-heptadecyl-3'-ethylimidazolium)-1,n-alkane dibromide, abbreviated as Gn, n=2, 4, 6, 8, 10). It has been found that both of the dyes could be adsorbed onto the monolayers of the gemini amphiphiles through the electrostatic and pi-pi interaction and stacked into H- or J-aggregate. The spacer of the gemini amphiphile showed good control over the aggregation of MTC: H-aggregate was favored when gemini amphiphiles with short spacer were applied, while J-aggregation was preferred in the case of longer spacer. Only J-aggregate was observed for PTC on gemini monolayer, regardless of the structure of the gemini amphiphiles. Interesting morphologies were observed for all the gemini/dye complex monolayers. Network structure and nanofibers were formed for the gemini/MTC films transferred below the plateau surface pressure and close to the collapse pressure, respectively. The ability of the complex monolayers to form nanofibers strongly depended on the component amphiphiles, G2>G4>G6, and no nanofibers were observed for G8/MTC and G10/MTC after the collapse. Only squared domains were observed for gemini/PTC monolayers. When both G2 and G10 were mixed, an individual control of the gemini amphiphiles over the aggregation of MTC in the complex monolayers was observed. The relationship among the spacer, dye structure, and aggregation was revealed.     

Lyotropic liquid crystalline phase behavior of amphiphilic monomers and polymers having a rod-like hydrophobic moiety

Distinct changes in the lyotropic mesophase behaviour of nonionic polyethyleneglycol containing amphiphiles are observed, when rigid, rod-like molecular units are introduced into the hydrophobic part of these amphiphiles, or when the amphiphiles are added as side chains to poly(methylhydrogene siloxane), yielding amphiphilic side chain polymers. Low molar mass amphiphiles with a dominating rigid, rod-like hydrophobic unit form planar-like micelles which aggregate into lamellar mesophases. Compared with their corresponding low molar mass amphiphiles, amphiphilic side chain polymers show a distinct stabilization of mesophases composed of anisometric micelles, i.e. hexagonal H₁-phases (built up by rod shaped micelles), and lamellar L -phases (built up by planarshaped micelles). In addition, several of the polymeric amphiphiles exhibit the formation of a lyotropic nematic N_c-phase regime. Optically isotropic I₁-phases composed of approximately spherical-like micelles are, on the other hand, disfavoured by the polymerfixation. Investigations of monodisperse amphiphilic side chain oligomers reveal a linear relationship between the thermal stability of the individual mesophases and the logarithm of the degree of polymerization. Changes in mesophase behaviour, due to the introduction of rigid, rod-like molecular units into the hydrophobic part of the low molar mass amphiphiles, are ascribed to packing restraints of the amphiphiles in the micelles. Alterations in mesophase behaviour which occur as a consequence of polymerfixation are discussed in terms of changes in micellar kinetics, packing restraints, and changes in the interaction between adjacent hydrophobic layers of neighbouring micelles.     

Formation and characterization of simple and mixed vesicles based on monomeric and oligomeric phosphate bipolar amphiphiles

Certain phosphate bipolar amphiphiles, both monomeric ( I and II ) and polymeric or rather oligomeric (poly- I and poly- II ), were used as basic materials for the preparation of simple and mixed vesicles. Specifically, it was found that oligomeric phosphate bipolar amphiphiles form stable vesicles in aqueous media. The same oligomeric bolaamphiphiles in mixture with their monomeric counterparts also form stable mixed vesicles with sonication; they are relatively less stable with the “thin film method.” Furthermore, it was shown that the method of spanning the membrane of didodecylphosphate vesicels with the dipolar amphiphile II is not effective for enhancing stability. © 1995 John Wiley & Sons, Inc.     

Photophysical and self‐assembly behavior of poly(amidoamine) dendrons with chromophore as scaffold: The effect of dendritic architecture

Two series of amphiphiles composed of hydrophilic poly(amidoamine) dendrons (from the first to the third generation) as the shell and hydrophobic aromatic chromophores (3,6‐di(maleimidyl)‐9‐phenyl carbazole and 9‐(4′‐maleimidyl phenyl)‐3‐maleimidyl carbazole) as the central scaffold were synthesized. The effect of dendritic architecture on the photophysical properties and the self‐assembly behavior of these amphiphiles were studied by UV–vis absorption spectroscopy, fluorescence spectroscopy, and transmission electron microscopy (TEM) measurements. Both the generation of dendritic shell and the location of dendrons at the chromophoric scaffold had great effect on the photophysical properties of these amphiphiles. In addition, different spherical aggregates were formed from these amphiphiles in the aqueous solution at different concentrations. Because of the combined effects of steric hindrance and architecture of dendritic shells, the amphiphiles from G2 dendron with central chromophore self‐organized into ordered aggregates more readily than that from G1 and G3. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4584–4593, 2008     

Supramolecular fluorophores for biological studies: phenylene vinylene-amino acid amphiphiles

We report here on a family of self-assembling fluorescent organic amphiphiles with a biomolecular L-lysine hydrophile and a photonically active phenylene vinylene hydrophobe. Unlike conventional amphiphiles, these segmented dendrimers feature a rigid, branched hydrophobe, and have packing characteristics controlled by the ratio of cross-sectional areas of the hydrophobe and hydrophile. In dilute solution, the amphiphiles form supramolecular aggregates, which are easily taken in by cells through an endocytic pathway, and have no discernible effect on cell proliferation or morphology. An analogous pyrene-based amphiphile was cytotoxic, suggesting that cell survival may be linked either to the self-assembling nature of the amphiphiles, or to the specific properties of the phenylene vinylene segment. The combination of photonic and biological components in these amphiphiles provides great potential for applications in sensing or delivery of molecules to intracellular targets.     

Introducing Chirality into Nonionic Dendritic Amphiphiles and Studying Their Supramolecular Assembly

Chiral head groups have been introduced into water‐soluble hydroxyl‐terminated nonionic amphiphiles and the impact of the head group stereochemistry on the supramolecular ultrastructures has been studied. Enantiomeric isomers were compared with the achiral meso form and the racemic mixture by means of cryogenic transmission electron microscopy and circular dichroism spectroscopy. Structurally, all amphiphiles are composed of the first‐generation hydrophilic polyglycerol head group coupled to a single hydrophobic hexadecyl chain through an amide linkage and diaromatic spacer. The enantiomers aggregate to form twisted ribbons with uniform handedness, whereas the meso stereoisomer and racemic mixture produce elongated assemblies, namely, tubules and platelets, but without a chiral ultrastructure. Simulations on the molecular packing geometries of the stereoisomers indicate different preferential assembly routes that explain the individual supramolecular aggregation behavior.     

A comparative Langmuir-Blodgett study on a set of covalently linked porphyrin-based amphiphiles: a detailed atomic force microscopic study

A set of covalently linked phenyl-amidophenyl-substituted porphyrin amphiphiles with n-C15H31 tails have been synthesized and completely characterized. These amphiphiles form good Langmuir-Blodgett (LB) films at the air/water interface. Mean molecular areas for the series were measured from the isotherms and found to increase as the number of aliphatic chains increased from one to four. No influence of the subphase pH was observed on the isotherms. LB films can be transferred successfully onto different solid surfaces. The LB films were characterized using tapping mode atomic force microscopy (AFM). Bis-, tris-, and tetra-substituted porphyrins were found to be fairly good film-forming amphiphiles, whereas irregular aggregates were seen in the case of the monosubstituted porphyrin amphiphile. Multilayers were also formed with tetra-substituted amphiphiles on mica. Detailed AFM studies of tetra-substituted amphiphiles have been carried out to investigate the effect of preparation procedure and solid substrates on film formation and transfer. The absorption and fluorescence spectra for the amphiphiles in solution and LB films deposited onto mica and glass were recorded, which demonstrated the successful transfer of LB films onto the substrates and provided more information about the arrangement of porphyrin molecules within the LB films. For comparison, self-assembled monolayers (SAMs) and the cast thin films of the amphiphiles were prepared and characterized.     

Chelating DTPA amphiphiles: ion-tunable self-assembly structures and gadolinium complexes

A series of chelating amphiphiles and their gadolinium (Gd(iii)) metal complexes have been synthesized and studied with respect to their neat and lyotropic liquid crystalline phase behavior. These amphiphiles have the ability to form ion-tunable self-assembly nanostructures and their associated Gd(III) complexes have potential as magnetic resonance imaging (MRI) contrast enhancement agents. The amphiphiles are composed of diethylenetriaminepentaacetic acid (DTPA) chelates conjugated to one or two oleyl chain(s) (DTPA-MO and DTPA-BO), or isoprenoid-type chain(s) of phytanyl (DTPA-MP and DTPA-BP). The thermal phase behavior of the neat amphiphiles was examined by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and cross polarizing optical microscopy (POM). Self-assembly of neat amphiphiles and their associated Gd complexes, as well as their lyotropic phase behavior in water and sodium acetate solutions of different ionic strengths, were examined by POM and small and wide angle X-ray scattering (SWAXS). All neat amphiphiles exhibited lamellar structures. The non-complexed amphiphiles showed a variety of lyotropic phases depending on the number and nature of the hydrophobic chain in addition to the ionic state of the hydration. Upon hydration with increased Na-acetate concentration and the subtle changes in the effective headgroup size, the interfacial curvature of the amphiphile increased, altering the lyotropic liquid crystalline structures towards higher order mesophases such as the gyroid (Ia3d) bicontinuous cubic phase. The chelation of Gd with the DTPA amphiphiles resulted in lamellar crystalline structures for all the neat amphiphiles. Upon hydration with water, the Gd-complexed mono-conjugates formed micellar or vesicular self-assemblies, whilst the bis-conjugates transformed only partially into lyotropic liquid crystalline mesophases.     

Synthesis of perfluoroalkyl-containing steroidal glycosides

A new kind of fluorine-containing amphiphiles -- perfluoroalkyl-containing steroidal glycos-ides were synthesized in good yield through perfluoroalkylation by means of sodium dithionite-initiatedaddition of R_FI to olefinic system. Preliminary study showed that these glycosides could formvesicles in aqueous medium as observed by electron microscopy.     

Investigation of the optimization of the recovery of mineral oil from water

A method has been derived to completely recover mineral oil dispersed in water. The method involves three steps: the emulsification of the mineral oil by adding amphiphiles, the breaking of the emulsion by adding salts and the extraction of the mineral oil by a non-polar aprotic solvent. Various amphiphiles and types and concentrations of salts were tested. By using amphiphiles with HLB numbers in the range 4.7 to 40 a complete recovery of the mineral oil could be obtained for a combination of salts Na₂SO₄ + NaH₂PO₄ with total ionic strength of 6 mol/L.     

Bilayers connected by threadlike micelles in amphiphilic mixtures: a self-consistent field theory study

Binary mixtures of amphiphiles in solution can self-assemble into a wide range of structures when the two species individually form aggregates of different curvatures. A specific example of this is seen in solutions of lipid mixtures where the two species form lamellar structures and spherical micelles, respectively. Here, vesicles connected by threadlike micelles can form in a narrow concentration range of the sphere-forming lipid. We present a study of these structures based on self-consistent field theory (SCFT), a coarse-grained model of amphiphiles. First, we show that the addition of sphere-forming lipid to a solution of lamella-former can lower the free energy of cylindrical, threadlike micelles and hence encourage their formation. Next, we demonstrate the coupling between composition and curvature; specifically, that increasing the concentration of sphere-former in a system of two bilayers connected by a thread leads to a transfer of amphiphile to the thread. We further show that the two species are segregated within the structure, with the concentration of sphere-former being significantly higher in the thread. Finally, the addition of larger amounts of sphere-former is found to destabilize the junctions linking the bilayers to the cylindrical micelle, leading to a breakdown of the connected structures. The degree of segregation of the amphiphiles and the amount of sphere-former required to destabilize the junctions is shown to be sensitive to the length of the hydrophilic block of the sphere-forming amphiphiles.     

Supramolecular assemblies of a new series of gemini-type schiff base amphiphiles at the air/water interface: in situ coordination, interfacial nanoarchitectures, and spacer effect

Great interest has been devoted to the gemini amphiphiles because of their unique properties. In this article, we report some interesting properties of the interfacial films formed by a series of newly designed gemini amphiphiles containing the Schiff base moiety. This novel series of gemini amphiphiles with their Schiff base headgroups linked by a hydrophobic alkyl spacer (BisSBC18Cn, n = 2, 4, 6, 8, 10) could be spread to form stable monolayers and coordinated with Cu(Ac)(2) in situ in the monolayer. The alkyl spacer in the amphiphiles has a great effect on the regulation of the properties of the Langmuir monolayers. A maximum limiting molecular area was observed for the monolayers of the gemini amphiphile with the spacer length of hexa- or octamethylene groups. Both the monolayers on water and on the aqueous Cu(Ac)(2) subphase were transferred onto solid substrates, and different morphologies were observed for films with different spacers. Nanonail and tapelike morphologies were observed for amphiphile films with shorter spacers (n = 2 and 4) on the water surface. Wormlike morphologies were observed for gemini films with longer spacers of C(8) and C(10) when coordinated with Cu(Ac)(2). An interdigitated layer structure was supposed to form in the multilayer films transferred from water or the aqueous Cu(Ac)(2) subphase.     

Structural variations in amphiphiles: Discoidal multivalent cations

Fourteen cationic multipolar amphiphiles have been synthesized with pyridinium or trimethylammonium head groups. The hydrophobic cores are planar ring systems (benzene or triphenylene) to which two, three, four, or six decylene or undecylene alkyl chains are attached by ester linkages. The hydrophilic head groups are bound to the outer ends of the alkyl chains.The aggregation of the molecules in water into micelles and lyotropic liquid crystals has been studied. Hexagonal phases are preferred to lamellar phases by these amphiphiles and in more dilute solutions some of these multipolar amphiphiles form cylindrical micelles.     

Nonionic diethanolamide amphiphiles with saturated hydrocarbon chains: Neat crystalline and lyotropic liquid crystalline phase behavior

The solid state and lyotropic phase behavior of a series of nonionic diethanolamide amphiphiles with increasing saturated hydrocarbon chain length (lauroyl, myristoyl, palmitoyl, and stearoyl) has been examined. All four saturated diethanolamide amphiphiles form a crystalline solid with two or three different polymorphic crystalline forms at room temperature. Melting points and associated enthalpies for these four amphiphiles increased with increasing chain length. Approximate partial binary phase diagrams have been constructed for each amphiphile/water system by combining Cross-Polarized Optical Microscopy (POM) and Small-Angle X-ray Scattering (SAXS) results. In the presence of water, all four diethanolamides form an L(α) phase, between 10% and 50% water content, and an L(2) phase with decreasing hydration and increasing temperature. In addition to the L(α) and L(2) phases, the shorter chain diethanolamide amphiphiles (lauroyl and myristoyl) also display a normal micellar phase (L(1)) at higher water contents, occurring to lower temperatures than the L(α) phase. By examining the effect of subtle molecular changes on both neat and lyotropic phase behavior, amphiphiles can be designed with properties tailored to a desired application.     

合成双分子膜的研究I. 单链1, 5取代萘刚性生色基的双亲化合物的合成及其在稀溶液中的自组织规律

本文首次报道了系列单链、1, 5取代萘刚性生色基团的两亲化合物C~nNaph(1,5)C~6N^+(n=16, 12, 10, 8, 6和4)的合成。用电镜、1^H NMR和DSC分别观察了该系列化合物在稀溶液中的聚集形态、聚集体内分子运动和物相变化。结果表明: 当n≥8时, 该系列双亲化合物在稀溶液中自组织成双层结构的囊泡, 泡壁为双分子膜。n=6时, 囊泡形状不完整。n=4时, 聚集体无确定形态。