Wormlike micelles formed by mixed cationic and anionic gemini surfactants in aqueous solution

The formation and the properties of wormlike micelles in aqueous solutions of mixed cationic and anionic gemini surfactants, 2-hydroxyl-propanediyl-α,ω-bis(dimethyldodecylammonium bromide) (12-3(OH)-12) and O,O′-bis(sodium 2-dodecylcarboxylate)-p-benzenediol (C12ϕC12), have been studied by steady-state and dynamic rheological measurements at 25 °C. With the addition of a small amount of C12ϕC12 into the solution of 12-3(OH)-12, the total surfactant concentration of which was always kept at 80 mmol L−1, the solution viscosity was strongly enhanced and its maximum was much larger than that of the mixed system of propanediyl-α,ω-bis(dimethyldodecylammonium bromide) (12-3-12) and C12ϕC12. The results of dynamic rheology measurements showed that 12-3(OH)-12/C12ϕC12 formed longer wormlike micelles in comparison with 12-3-12/C12ϕC12. This was attributed to the effect of hydrogen bonding occurring between 12-3(OH)-12 molecules, which was an effective driving force promoting micellar growth. As few C12ϕC12 participated in the micelles, the electrostatic attraction between the oppositely charged head groups of 12-3(OH)-12 and C12ϕC12 made the molecules in the aggregates pack more tightly. This reinforced the hydrogen-bonding interactions and greatly promoted the micellar growth.

On the addition of a small amount of C12ϕC12, the hydrogen-bonding interaction between 12-3(OH)-12 molecules is greatly enhanced, resulting in longer micelles and a viscous solution.Figure optionsDownload high-quality image (59 K)Download as PowerPoint slideResearch highlights
► Wormlike micelle formed in aqueous solutions of mixed gemini surfactants.
► Intermolecular hydrogen-bonding interaction promotes growth of the wormlike micelles.
► Electrostatic attraction reinforces hydrogen-bonding interactions.