73 research outputs found
Adsorption of MultiLamellar tubes with a temperature tunable diameter at the air-water interface: a process driven by the bulk properties
The behavior at the air/water interface of multilamellar tubes made of the
ethanolamine salt of the 12-hydroxy stearic acid as a function of the
temperature has been investigated using Neutron Reflectivity. Those tubes are
known to exhibit a temperature tunable diameter in the bulk. We have observed
multilamellar tubes adsorbed at the air/water interface by specular neutron
reflectivity. Interestingly, at the interface, the adsorbed tubes exhibit the
same behavior than in the bulk upon heating. There is however a peculiar
behavior at around 50\degree for which the increase of the diameter of the
tubes at the interface yields an unfolding of those tubes into a multilamellar
layer. Upon further heating, the tubes re-fold and their diameter re-decrease
after what they melt as observed in the bulk. All structural transitions at the
interface are nevertheless shown to be quasi-completely reversible. This
provides to the system a high interest for its interfacial properties because
the structure at the air/water interface can be tuned easily by the
temperature
Glycerol as a cheap, safe and sustainable solvent for the catalytic and regioselective ÎČ,ÎČ-diarylation of acrylates over palladium nanoparticles
Herein we show that glycerol can be considered as a promising cheap and green solvent for the regioselective ÎČ,ÎČ-diarylation of alkenes. Whereas this reaction is generally catalyzed under an inert atmosphere by expensive phosphine or carbene-palladium complexes, we show here that the diarylation of alkenes can be conveniently achieved in glycerol in the presence of air-stable palladium nanoparticles. These palladium nanoparticles were stabilized over a sugar-based surfactant derived from biomass. By an adjustment of the reaction temperature, we were able to control the mono- and diarylation step of alkenes, thus offering a convenient route to unsymmetrical diarylated alkenes. At the end of the reaction, the diarylated alkenes were cleanly and selectively extracted from the glycerol-palladium catalytic phase using supercritical carbon dioxide, thus affording a convenient purification work-up. Within the framework of green chemistry, this work combines (i) catalysis in a cheap, safe and sustainable medium, (ii) easily made and air-stable palladium nanoparticles as the catalyst, and (iii) a clean and selective extraction of the reaction products with supercritical carbon dioxide
Mixture of fatty alcohols and alkyl polyglucosides stabilizing water-in-water emulsions
The combination of surfactants and fatty alcohols leads to the formation of lamellar gel network (LGNs) which are widely used in cosmetic and pharmaceutical industries. Alkyl polyglucosides are known to stabilize oil-in-water emulsions and here, we report their use in combination with fatty alcohol for the stabilization of all-aqueous water-in-water (W/W) emulsions based on dextran-in-poly(ethylene glycol). Two different APGs were used: decyl glucoside and lauryl glucoside. We systematically studied the influence of the concentrations of APGs, and the molar ratio between the APGs and decanol as model fatty alcohol on the size and stability of the aqueous emulsion droplets with time. The self-assembled structure formed by decanol/APGs was characterized by using Small Angle X-ray Scattering and confocal microscopy, and shown to be lamellar in the bulk phase and probably also at the surface of dextran-rich droplets. We also demonstrated that the stabilization of W/W emulsions can be extended to other alkyl polyglucoside and to other fatty alcohols. In addition, we reported the production of a foam using such W/W emulsions as the continuous phase. Our results show that it is possible to stabilized W/W emulsions using LGNs based on different APGs and fatty alcohols, which will undoubtedly expand the use of W/W emulsions for various fields.ULN
Multi-scale structural characterizations of fatty acid tubes with temperature tuneable diameter in bulk and at the air/water interface
International audienceThe use of agricultural resources for industrial purposes will undoubtedly be one of the major challenges of the 21st century, either from the energetic point of view by the progressive replacement of fossil fuels or with respect to non-energy uses by making available new organic âbiosynthonsâ to the chemicals industry. In such a context, we demonstrate here the strong potential of dispersions of saturated fatty acids and their hydroxylated derivatives, extracted from biological compounds of plant origin, as a new class of green surfactants
Antagonistic chemical coupling in self-reconfigurable hostâguest protocells
Multi-compartmentalised soft micro-systems are used as models of synthetic protocells. Here, the authors developed nested hostâguest protocell constructs capable of self-reconfiguration in response to changes in pH generated by antagonistic modes of enzyme-mediated coupling
Self-assembly of hollow cones in a bola-amphiphile/hexadiamine salt solution
International audienc
Double Emulsion Droplets as a Plausible Step to Fatty Acid Protocells
Abstract It is assumed that life originated on the Earth from vesicles made of fatty acids. These amphiphiles are the simplest chemicals, which can be present in the prebiotic soup, capable of selfâassembling into compartments mimicking modern cells. Production of fatty acid vesicles is widely studied, as their growing and division. However, how prebiotic chemicals require to further yield living cells encapsulated within protocells remains unclear. Here, one suggests a scenario based on recent studies, which shows that phospholipid vesicles can form from double emulsions affording facile encapsulation of cargos. In these works, waterâinâoilâinâwater droplets are produced by microfluidics, having dispersed lipids in the oil. Dewetting of the oil droplet leaves the internal aqueous droplet covered by a lipid bilayer, entrapping cargos. In this review, formation of fatty acid protocells is briefly reviewed, together with the procedure for preparing double emulsions and vesicles from double emulsion and finally, it is proposed that double emulsion droplets formed in the deep ocean where undersea volcano expulsed materials, with fatty acids (under their carboxylic form) and alkanols as the oily phase, entrapping hydrosoluble prebiotic chemicals in a double emulsion droplet core. Once formed, double emulsion droplets can move up to the surface, where an increase of pH, variation of pressure and/or temperature may have allowed dewetting of the oily droplet, leaving a fatty acid vesicular protocell with encapsulated prebiotic materials
Self-assembly of fatty acids: from foams to protocell vesicles
Fatty acids are potentially versatile substitutes to phospholipids and synthetic surfactants in materials chemistry and biophysics. However, sodium (or potassium) salts of saturated long chain fatty acids (SLCFAs) are long known to be soluble at a high temperature but they crystallize below their Krafft point, hampering their use for multiple applications. Recent advances have shown that under particular experimental conditions, i.e., by using a 'good' counter-ion, SLCFAs can be dispersed in water into various supramolecular assemblies which opens up new fields of research and applications. Here, recent studies on the self-assembly of fatty acids are commented and some potential applications are proposed and discusse
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