Effect of surfactant headgroup on low-fluorine-content CO2-philic hybrid surfactants

• Synthesis and characterization of a hybrid sulfoglutarate surfactant.
• Hybrid CF2/AOT14GLU is a CO2-philic surfactant with a low level of fluorination.
• Surfactant CO2-philicity can be tuned by hydrophilic modification.
• Hybrid CF2/AOT14GLU provides potential environmental and economic advantages.

The article addresses the role of surfactant headgroup structure on hybrid surfactant performance for water-in-CO2 (w/c) microemulsion stabilization. The synthetic procedure, aqueous properties, and phase behaviour of a new hybrid sulfoglutarate surfactant are described. The sulfoglutarate version has an extra methylene group incorporated into the hydrophilic headgroup. The related hydrocarbon (AOT14 and AOT14GLU) and fluorocarbon (di-CF2 and di-CF2GLU) surfactants were used to form w/c microemulsions. For these two groups, the aqueous properties and w/c phase stability of both sulfoglutarates and sulfosuccinates were found to be similar. The newly synthesized hybrid CF2/AOT14GLU (sodium (4H,4H,5H,5H,5H-pentafluoropentyl-2,2-dimethyl-1-propyl)-2-sulfoglutarate) proved to be more efficient than the normal sulfosuccinate, hybrid CF2/AOT14 in terms of the aqueous behaviour and w/c phase stability. Hybrid CF2/AOT14GLU more effectively decreased the air-water surface tension by ∼2 mN m−1 and lowering the cloud pressures on CO2 by ∼150 bar.

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