Interaction of Alkanes with Monolayers of Nonionic Surfactants

Aveyard, Robert; Binks, Bernard P.; Fletcher, Paul D. I.; Macnab, J.

doi:10.1021/la00007a034

Cited by 42 publications

(42 citation statements)

References 4 publications

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“…38 In addition, several past studies have examined the penetration of oils into surfactant-laden interfaces. 39,40 These studies have provided detailed insights into the mixing of the oil with the surfactant-tail region of the interfaces, and suggest avenues for future studies that may provide additional insight into the interactions of lipids and LCs described in this paper. 39,40 Our results are also consistent with the proposition that the driving force for phase separation is a lower energy state of the homeotropically oriented film of LC: by concentrating the PEGlipid in PEG-lipid-rich domains, the composition of PEG-lipid within the remaining area of the interface is decreased sufficiently that the LC can adopt a homeotropic orientation.…”

Section: Discussion Of Mechanism Of Phase Separationmentioning

confidence: 78%

“…39,40 These studies have provided detailed insights into the mixing of the oil with the surfactant-tail region of the interfaces, and suggest avenues for future studies that may provide additional insight into the interactions of lipids and LCs described in this paper. 39,40 Our results are also consistent with the proposition that the driving force for phase separation is a lower energy state of the homeotropically oriented film of LC: by concentrating the PEGlipid in PEG-lipid-rich domains, the composition of PEG-lipid within the remaining area of the interface is decreased sufficiently that the LC can adopt a homeotropic orientation. Several prior studies have established that elastic strain can lead to LC films that possess a lower energy when the LC assumes a homeotropic orientation at one interface as compared to a planar orientation.…”

Section: Discussion Of Mechanism Of Phase Separationmentioning

confidence: 78%

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Nematic ordering drives the phase separation of mixed monolayers containing phospholipids modified with poly(ethylene glycol) at aqueous–liquid crystal interfaces

2010

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We report that homogeneous Langmuir monolayers formed from mixtures of dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylethanolamine conjugated to poly(ethylene glycol) (M w ¼ 2000 g mol À1 , DPPE-PEG2000), when transferred onto interfaces formed between aqueous phases and nematic liquid crystals (LCs), phase separate in a manner that leads to patterned orientations of the LCs. Quantitative fluorescence microscopy establishes that the patterned orientations of the LCs correspond to coexisting interfacial phases that differ in total lipid density as well as lipid composition. Subsequent investigation determined that the interfacial phase separation of lipid is driven by the combined influence of the nematic ordering of the LC and the interactions between the PEG chains of DPPE-PEG2000. The latter effects impact the packing of the lipid monolayer and thus its interaction with the LC. In contrast to the phase separation of PEG-lipids within Langmuir films, where the repulsive interactions between PEG chains suppress phase separation at high interfacial densities of lipid, the results of our study indicate that repulsive interactions between PEG chains promote the phase separation of lipid at the aqueous-LC interface. Our results reveal a fundamentally new mechanism leading to control of the interfacial phase behavior of PEG-lipids, and suggest new principles for manipulation of the organization of multi-component lipid assemblies at interfaces.

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Section: Discussion Of Mechanism Of Phase Separationmentioning

confidence: 78%

Section: Discussion Of Mechanism Of Phase Separationmentioning

confidence: 78%

Nematic ordering drives the phase separation of mixed monolayers containing phospholipids modified with poly(ethylene glycol) at aqueous–liquid crystal interfaces

2010

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“…18 Although PIT studies give only circumstantial evidence of oil penetration, they have been given added validity by fairly recent studies of Aveyard, Thomas, and co-workers. 19,20 These workers used a combination of surface tension measurements and neutron reflectivity studies to assess the penetration of hydrocarbon oils of varying chain lengths into surfactant monolayers at a planar air/water interface. 19,20 The results of their studies confirmed the conclusions from their PIT studies, in that there was oil penetration of the interfacial surfactant monolayer, with the extent of this penetration increasing with decreasing size of oil and increasing length of the surfactant hydrophobic moiety.…”

Section: Resultsmentioning

confidence: 99%

“…19,20 These workers used a combination of surface tension measurements and neutron reflectivity studies to assess the penetration of hydrocarbon oils of varying chain lengths into surfactant monolayers at a planar air/water interface. 19,20 The results of their studies confirmed the conclusions from their PIT studies, in that there was oil penetration of the interfacial surfactant monolayer, with the extent of this penetration increasing with decreasing size of oil and increasing length of the surfactant hydrophobic moiety. It is important to note, however, that although these neutron reflectivity measurements confirm that oil penetration occurs, they do not give any reliable information about how varying the concentration of oil incorporated will alter the extent of penetration because the experiments so far performed have been carried out under conditions of oil saturation of the monolayer.…”

Section: Resultsmentioning

confidence: 99%

Effect of Oil on the Level of Solubilization of Testosterone Propionate into Nonionic Oil-in-Water Microemulsions

Malcolmson¹,

Satra²,

Kantaria³

et al. 1998

Journal of Pharmaceutical Sciences

154

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The level of solubilization of the drug testosterone propionate into 2% w/w oil-in-water (o/w) microemulsions, stabilized by the nonionic surfactant polyoxyethylene 10-oleyl ether (Brij 96) and containing a range of oils, has been determined. Although testosterone propionate was readily soluble in the ethyl esters ethyl oleate, ethyl caprylate, and ethyl butyrate, and the triglycerides soybean oil, Miglyol 812, and tributryin, and the alkene 1-heptene, only microemulsions containing the ethyl esters and the triglyceride oils exhibited a significant increase in solubilization over the corresponding micellar solution (i.e., surfactant solution in the absence of oil). Furthermore, the increase in drug solubility observed in the microemulsion systems was not related to the solubility of the drug in the bulk oil. That is, while the smaller molecular volume oils, such as ethyl butyrate, exhibited a greater capacity for the drug, microemulsions containing these oils were only marginally better at solubilizing the drug than the corresponding micellar solution. In contrast, microemulsions containing the larger molecular volume oil, Miglyol 812, gave levels of drug solubilization almost three times those containing ethyl butyrate, yet the bulk capacity for drug in this oil was less than half that of ethyl butyrate. Light scattering and phase inversion temperature studies suggested that the structure of the microemulsion was sensitive to the oil being used, in that, at the low oil concentrations used in this study, the smaller molecular volume oils generally penetrated the interfacial surfactant monolayer in much the same way as a cosurfactant, causing an alteration, presumably a dilution, of the relatively concentrated polyoxyethylene region close to the hydrophobic core, thereby destroying one of the main loci of drug solubilization and counteracting any advantages encountered due to the high solubility of the drug in the bulk oil.

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“…32 These results provide convincing evidence that the interaction of oils with the surfactant monolayer has important consequences for a wide range of phenomena, including microemulsion formation, 33 and that various physical processes can give rise to very low interfacial tension with the probability of oil spreading on the surface of the aqueous surfactant solution either as a continuous oil film over the surface or as discrete lenses. 34 The interfacial tension measurements of a series of experiments in which oil was admixed with a blend of surfactant and cosurfactant showed slight variability in lowering the interfacial tension by changing the surfactant/cosurfactant ratios where the interfacial tension approached almost 0 in both systems with ncentrations up to 30% oil. Furthermore, the variation of the Km ratio from 1.3:1 to 3:1 with the same oil resulted in a greater decrease in interfacial tension.…”

Section: Interfacial Tension Measurementsmentioning

confidence: 99%

Preparation and physicochemical characterization of dioctyl sodium sulfosuccinate (aerosol OT) microemulsion for oral drug delivery

El-Laithy

2003

AAPS PharmSciTech

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The performance of dioctyl sodium sulfosuccinate (aerosol OT) in the development of a pharmaceutically acceptable, stable, self-emulsifying water continuous microemulsion with high dilution efficiency was assessed. A pseudoternary microemulsion system was constructed using aerosol OT/medium-chain triglycerides with oleic acid/glycerol monooleate and water. The model microemulsion was characterized with regard to its electroconductive behavior, eosin sodium absorption, interfacial tension, and droplet size measurements after dilution with water. The percolation transition law, which makes it possible to determine the percolation threshold and to identify bicontinuous structures, was applied to the system. The interfacial tension changes associated with the microemulsion formation revealed ultralow values up to 30% oil at a surfactant/cosurfactant ratio of 3:1. Moreover, the investigated particle size and polydispersity using photon correlation spectroscopy after dilution with excess of the continuous phase proved the efficiency of the microemulsion system as a drug carrier that ensures an infinitely dilutable, homogeneous, and thermodynamically stable system.

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Interaction of Alkanes with Monolayers of Nonionic Surfactants

Cited by 42 publications

References 4 publications

Nematic ordering drives the phase separation of mixed monolayers containing phospholipids modified with poly(ethylene glycol) at aqueous–liquid crystal interfaces

Nematic ordering drives the phase separation of mixed monolayers containing phospholipids modified with poly(ethylene glycol) at aqueous–liquid crystal interfaces

Effect of Oil on the Level of Solubilization of Testosterone Propionate into Nonionic Oil-in-Water Microemulsions

Preparation and physicochemical characterization of dioctyl sodium sulfosuccinate (aerosol OT) microemulsion for oral drug delivery

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