Surface properties, aggregation behavior and micellization thermodynamics of a class of gemini surfactants with ethyl ammonium headgroups

Cationic gemini surfactant homologues alkanediyl-α,ω-bis(dodecyldiethylammonium bromide), [C12H25(CH3CH2)2N(CH2)SN(CH2CH3)2C12H25]Br2 (where S = 2, 4, 6, 8, 10, 12, 16, 20), referred to as C12CSC12(Et) were synthesized systematically. This paper focused on various properties of the above gemini surfactants in order to give a full understanding of this series of surfactants. The following points are covered: (1) surface properties, which include (i) effect of the spacer carbon number on the general properties and (ii) the effect of added NaBr on the general surface properties; (2) aggregation behavior in bulk solution, including (i) morphologies of above gemini surfactants classed as having short spacers, middle-length spacers and long spacers and (ii) superior vesicle stability against high NaBr concentration for the long spacer gemini surfactants; (3) thermodynamic properties during micellization and the effect of spacer carbon number on them; and (4) perspectives for the further use and application of these compounds.

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► A systematic series of gemini surfactants have been synthesized.
► Surface, aggregation and thermodynamic properties are reported.
► The variation of headgroup structure affects the properties of these gemini surfactants.
► Hydrophobic effects are emphasized for a surfactant with multi-polar headgroups.