Surface activity of a fluorinated carbohydrate ester in water/carbon dioxide emulsions

in Journal of Colloid & Interface Science (2013), 398

The water/carbon dioxide (W/CO2) interfacial activity and emulsifying capacity of hydrocarbon and fluorinated carbohydrate esters are investigated of the first time and compared to the performance of ... [more ▼]

The water/carbon dioxide (W/CO2) interfacial activity and emulsifying capacity of hydrocarbon and fluorinated carbohydrate esters are investigated of the first time and compared to the performance of sodium-bis(2-ethylhexyl)sulfosuccinate (AOT). The reduction of the W/CO2 interfacial tension was measured using a pendant drop tensiometer equipped with a cell view pressurized with CO2 at 80 bar and 45 °C. It was found that the interface stabilization improved in the order AOT < 6-O-myristoyl mannose < 6-O-(2H,2H,3H,3H-perfluoroundecanoyl)-D-mannose. In the latter case, a drastic reduction of the W/CO2 interfacial tension was observed (85% reduction, interfacial tension at the equilibrium = 3.6 mN/m), which emphasizes the advantage of using a fluorinated CO2-philic tail and the potential of sugars as hydrophilic head. The formulation of stable W/CO2 emulsions was also achieved using the fluorinated mannose derivative. This study paves the way to the design of a novel class of competitive surface active agents for W/CO2 emulsions. [less ▲]

Synthesis of microsphere-loaded porous polymers by combining emulsion and dispersion polymerisations in supercritical carbon dioxide

in Chemical Communications (2012), 48(67), 8356-8358

Highly porous materials were produced by acrylamide polymerisation templated by supercritical CO2-in-water emulsions using new fluorinated glycosurfactants. Properties of the resulting polymer scaffolds ... [more ▼]

Highly porous materials were produced by acrylamide polymerisation templated by supercritical CO2-in-water emulsions using new fluorinated glycosurfactants. Properties of the resulting polymer scaffolds were tuned by performing dispersion polymerisations within their cavities filled with supercritical CO2. [less ▲]

Design of sugar-based surface active agents for emulsion polymerization in supercritical carbon dioxide

Conference (2012, May 10)

The use of aqueous dispersed media, such as emulsions, has many advantages over solution processes for chemical transformations and polymerization reactions, i.e. limited environmental impact, ease of ... [more ▼]

The use of aqueous dispersed media, such as emulsions, has many advantages over solution processes for chemical transformations and polymerization reactions, i.e. limited environmental impact, ease of products recovery and increased reaction rate. Emulsions are usually implemented from a water/organic solvent mixture in the presence of a surfactant. However, supercritical carbon dioxide (scCO2) (Pc =74 bars; Tc = 31°C) constitutes an interesting alternative to the traditional organic solvents in these heterogeneous systems because it is inexpensive, non-toxic, non-inflammable and environmentally friendlier. In this context, we developed a novel class of surfactants for the stabilization of H2O/scCO2 emulsions, i.e. fluorinated modified carbohydrates. The hydrophilic head of the surfactant consists in a sugar moiety whereas a fluorinated tail is specifically located in the scCO2 phase. The strategies for the synthesis of these carbohydrates esters rely on selective lipase-catalyzed modifications of sugars and on the versatile thiol-Michael addition reaction. The ability of these molecules to decrease the H2O/scCO2 interfacial tension and to stabilize such emulsions will be presented. Finally, high internal phase scCO2-in-water emulsion (HIPE) were prepared with these new surfactants and used as template for the acrylamide polymerization. The monomer is polymerized in the continuous aqueous phase before removing the CO2 droplets (at least 70 % of the total volume). The resulting permeable porous polymers, called polyHIPEs, exhibit highly interconnected voids (cfr SEM picture) and should be valuable in many applications including support for catalyst, filtration process, immobilization of proteins, etc. [less ▲]

Combination of lipase catalysis and thiol-Michael addition for the synthesis of carbohydrate esters used as stabilizers in supercritical carbon dioxide emulsions

Poster (2011, November 21)

The use of aqueous dispersed media, such as emulsions and miniemulsions, has many advantages over solution processes for chemical transformations and polymerization reactions, i.e. limited environmental ... [more ▼]

The use of aqueous dispersed media, such as emulsions and miniemulsions, has many advantages over solution processes for chemical transformations and polymerization reactions, i.e. limited environmental impact, ease of products recovery and increased reaction rate. Although, dispersed media are usually implemented from water/solvent mixtures, supercritical carbon dioxide (scCO2) (Pc =74 bars; Tc = 31°C) constitutes an interesting alternative to the traditional organic solvents because it is inexpensive, non-toxic, non-flammable and environmentally friendlier. In this context, we develop a novel class of surface active compounds able to stabilize water/scCO2 emulsions, i.e. fluorinated modified carbohydrates. The hydrophilic head of the surfactant consists in a sugar moiety whereas the fluorinated tail has a strong affinity for the scCO2 phase. These carbohydrate esters are prepared by a two-step strategy which takes advantage of the selectivity of enzymatic catalysis and the versatility of the thiol-Michael addition reaction. The new thiolated mannose intermediate is a useful building block for the incorporation of unprotected sugar moieties into complex molecules. The surface active properties of the fluorinated derivatives have been evaluated as well as their use as stabilizers for the preparation of microparticles and highly porous polymer materials in scCO2. [less ▲]