Phosphorylation of Mono- or Di-octadienyl-D-xylosides. Influence towards Surfactant Properties

International audienc

Effect of Surfactants on the Deformation and Detachment of Oil Droplets in a Model Laminar Flow Cell

Sugar-based surfactants are increasingly present in the development of eco-friendly detergents due to current regulations and consumer demand. In order to assess the degreasing performance of these new surfactants, the behavior of model oil droplets subjected to the action of a flow of surfactant solutions of different concentrations was studied in a laminar flow cell and related to the physico-chemical properties measured at the liquid/liquid (interfacial tension) and solid/liquid/liquid interfaces (contact angle). With the surfactant solutions and the model oils employed in this study, three main behaviors were observed when a critical flow rate was reached: elongation, fragmentation or spontaneous detachment of the droplet. The analysis of the results leads to a correlation between the droplet behavior and the balance of the forces applied on the droplet in its initial position, in particular the gravity force Fg, which tends to move the oil droplet upwards (given the density difference), and the capillary force Fc, which tends to keep the droplet spherical. A state diagram could be established, based on the dimensionless Bond number (Fg/Fc) and cosθ, θ being the initial contact angle of the drop on the surface before the establishment of the flow. One can thus predict the droplet behavior as a function of the system initial characteristics. The results allowed the comparison of degreasing performance of the different surfactants used and illustrated the potential of AlkylPolyPentosides (APP) for detergent formulations

Selective complexation of copper ions in monolayers of a new amphiphilic cage molecule at the liquid/air and liquid/liquid interfaces

The authors report studies of a newly synthesized cyclam deriv. with 4 chain substituents (tetra-(N-2-tetradecyl-carboxamidoethyl)-tetraazacyclotetradecane; TC14) which could be of interest for the selective liq.-liq. extn. of cations. The authors studied the monolayer properties of TC14 mols. spread at the aq. soln./air interface by surface pressure-area isotherm measurements and Brewster angle microscopy. Surface pressure-area isotherms measurements were also performed at the aq. soln./decane interface with a new interfacial Langmuir trough. The effects of the salt concn. in solns. (CuCl2, NaCl and CsCl) on the TC14 surface pressure-area isotherms were related to the binding of the cations to the cage mol. at the interface. The film was sensitive to the presence of ions in the aq. phase, particularly in the high-pressure region of the isotherm, where the film collapses. The Langmuir balance technique revealed the preferential complexation of Cu2+ ions by the cage mol. in the interface and permitted one to detect the presence of very small ion concns. in the subphase

Effect of Surfactants on the Deformation and Detachment of Oil Droplets in a Model Laminar Flow Cell

Sugar-based surfactants are increasingly present in the development of eco-friendly detergents due to current regulations and consumer demand. In order to assess the degreasing performance of these new surfactants, the behavior of model oil droplets subjected to the action of a flow of surfactant solutions of different concentrations was studied in a laminar flow cell and related to the physico-chemical properties measured at the liquid/liquid (interfacial tension) and solid/liquid/liquid interfaces (contact angle). With the surfactant solutions and the model oils employed in this study, three main behaviors were observed when a critical flow rate was reached: elongation, fragmentation or spontaneous detachment of the droplet. The analysis of the results leads to a correlation between the droplet behavior and the balance of the forces applied on the droplet in its initial position, in particular the gravity force Fg, which tends to move the oil droplet upwards (given the density difference), and the capillary force Fc, which tends to keep the droplet spherical. A state diagram could be established, based on the dimensionless Bond number (Fg/Fc) and cosθ, θ being the initial contact angle of the drop on the surface before the establishment of the flow. One can thus predict the droplet behavior as a function of the system initial characteristics. The results allowed the comparison of degreasing performance of the different surfactants used and illustrated the potential of AlkylPolyPentosides (APP) for detergent formulations

Amphiphilic azobenzenes: Antibacterial activities and biophysical investigation of their interaction with bacterial membrane lipids

International audienc

Modelization of the Release from a Tetradecane/Water/Hexadecane Multiple Emulsion: Evidence of Significant Micellar Diffusion

International audienceThe release of tetradecane from a multiple emulsion of the type tetradecane/water/hexadecane was studied experimentally using the differential scanning calorimetry technique. The kinetics of the tetradecane release was measured for three formulations containing different concentrations of hydrophilic surfactant (2%, 4%, and 7%). A new mass transfer model derived from the shrinking core model was developed. The values of the model parameters deduced from the least-squares fittings led to the determination of the tetradecane diffusivity. Thus, the preponderant mechanism of mass transfer was proved to be micellar diffusion and not molecular diffusion. This conclusion was confirmed by considering the effect of the change in the hydrophilic surfactant concentration

Comparison of enzymic activity and nanostructures in water/ethanol/Brij 35 and water/1-pentanol/Brij 35 systems

The kinetics of enzyme-catalyzed alc. oxidn. has been measured in liq. water/ethanol/Brij 35 and water/1-pentanol/Brij 35 systems, essentially in the water-rich regions. For the ethanol systems it was found that the enzymic activity sharply decreases with increasing alc. concn. independently of the surfactant concn. between 0 and 22 mass %. In the case of the 1-pentanol systems the enzymic activity decreases also with increasing alc. concn., but this decrease can considerably be attenuated by adding increasing amts. of surfactant. To explain these results at the nanometer level, small-angle neutron-scattering (SANS) expts. have been carried out on these systems. The comparison of the scattering and the kinetic measurements suggests the following interpretation. In all cases, the enzymic activity depends on the concn. of the alc. in the aq. phase or in the aq. pseudophase contg. the enzyme. A certain amt. of alc. may be present in an org. pseudophase formed by direct micelles. In the case of the 1-pentanol systems the alc. participates in the structuration of the micelles and is concd. in the micelles, whereas in the case of the ethanol systems the alc. remains essentially in the aq. pseudophase and even destroys the micelles. These results suggest that in some cases enzymic activity can be used as a probe to detect some aspects of the mol. organization of a complex liq

Destabilisation of Water-in-Crude Oil Emulsions by Silicone Copolymer Demulsifiers

Asphaltene aggregates are known to form viscoelastic film preventing the coalescence of droplets in water-in-oil emulsions formed during crude oil exploitation. Since phase separation is necessary for oil refining process, demulsifying additives are used. It was found that formulations based on polysiloxane copolymers promote separation of water from crude oil even at very low concentration (few tens of ppm). Two alternative scenarios of emulsion destabilisation can be envisaged: (i) dissolution of asphaltene aggregates or (ii) displacement of the asphaltene network by adsorption of the more surface active copolymer into void sites at the oil/water interface. In order to reveal the mechanism of destabilisation, interactions between asphaltene aggregates and copolymer were explored. For that purpose various techniques have been employed: small angle X-ray scattering allowing the determination of the influence of copolymer on the size of asphaltene aggregate; capacity of copolymer to displace asphaltene aggregates initially adsorbed on silica particles (which simulate water droplets); Atomic Force Microscopy (AFM) was used to observe the influence of copolymer on the interfacial structure of asphaltene films spread on water surface