Interfacial tension and the behavior of microemulsions and macroemulsions of water and carbon dioxide with a branched hydrocarbon nonionic surfactant

The effects of supercritical CO2 formulations on the removal of high-dose ion-implanted photoresists

“…1 displays two CO 2 -philic tails on molecular backbone, which are a propylene oxide (PO) oligomer and a moderately branched hydrocarbon. The dual tails of surfactant EH-3 decrease A TT and increase the surfactant absorption at the water-CO 2 interface more effectively than TMN-3 consisting of one tail, leading to a sufficiently low value of c down to about 1 mN/m [26]. Similar results were obtained by varying the surfactant concentration from (1 to 5) wt.% at given pressures.…”

“…As seen from the tabulated values, the W S increased with the addition of surfactant in scCO 2 and the enhancement induced by EH-3 is obviously greater than that by TMN-3 at the same operating conditions (W S ¼ 5:01 for EH-3 and W S ¼ 4:06 for TMN-3 at 25 MPa, respectively). This is attributed to the stubby surfactant tails favoring the formation of a stable W/CO 2 microemulsion and subsequent lowering the interfacial tension c. The stubby tails on the EH-3 and TMN-3 backbone weaken the interactions between tails (reducing A TT ), which will raise the solubility of EH-3 and TMN-3 in scCO 2 and the adsorption of surfactants at the water-CO 2 interface by enhancing the solvation of surfactant tails with CO 2 [26,32]. The stubby tails may also be expected to inhibit the interpenetration due to steric repulsion upon approach of two microemulsion droplets and lead to weaker inter-droplet interactions, which are unusually strong in the weak solvent CO 2 , thereby reducing the chance for phase separation [25].…”

“…While hydrocarbon-based surfactants are difficult to dissolve in scCO 2 , co-solvents and specific additives are usually added to increase the solubility of hydrocarbon surfactants in scCO 2 [22][23][24]. Branched alkyl hydrocarbon surfactants formed by methylation of chain tips have higher solubility in scCO 2 than linear chain hydrocarbon surfactants due to their good affinities with scCO 2 and large steric volume of CO 2 -philic groups [25,26]. The post-etch residues in vias and trenches in patterned low-k porous methylsilsesquioxane (pMSQ) interlayer dielectrics were removed in solutions containing branched hydrocarbon surfactant polyoxyethylene 2,6,8-triethyl-4-nonyl ether (5b-C 12 E 8 ), water, and scCO 2 [27].…”

Switchable Diamine Surfactants for CO2 Mobility Control in Enhanced Oil Recovery and Sequestration

“…[15] In this study temperature measurements were extended to 120 °C. Gibbs adsorption equation (Equation 2) was used below the CMC to determine the molar surface density of the surfactant monolayer.…”

Understanding aqueous foam with novel CO2-soluble surfactants for controlling CO2 vertical sweep in sandstone reservoirs

“…Sanders et al (2010) reported the design and synthesis of a new class of twin-tailed surfactants based on glycerin and designed for the scCO 2 -water interface, whose performance was better than a linear secondary alcohol CO 2 -soluble surfactant. Adkins et al (2010a, b) and Chen et al (2010) have proven that a branched hydrocarbon nonionic surfactant can effectively reduce the contact of CO 2 and water phases and raise the surface pressure and the surfactant efficiency (the concentration to produce 20 mN/m interfacial tension reductions). Chen et al (2012) developed a switchable ethoxylated cationic CO 2 -philic surfactant which was able to stabilize CO 2 /water foams up to 182 g/L at 120°C, 3400 psia.…”