Wormlike micelles formed using Gemini surfactants with quaternary hydroxyethyl methylammonium headgroups

Area of Science:

• Colloid and Surface Chemistry
• Materials Science

Background:

• Gemini surfactants are known for their unique aggregation properties in aqueous solutions.
• The headgroup structure significantly influences surfactant self-assembly and resulting solution properties.

Purpose of the Study:

• To investigate the aggregation behavior of novel Gemini surfactants, butane-1,4-bis(hydroxyethyl methylalkylammonium) bromides (m-4-m MEA), in aqueous media.
• To understand the role of hydroxyl headgroups and alkyl chain length in micelle formation and viscoelasticity.

Main Methods:

• Rheological measurements (steady and dynamic) to assess viscoelastic properties.
• Cryo-transmission electron microscopy (cryo-TEM) and small-angle X-ray scattering (SAXS) to confirm micelle structure.

Main Results:

• m-4-m MEA surfactants formed viscous fluids at low concentrations.
• 14-4-14 MEA solutions exhibited highly viscoelastic wormlike micelles, confirmed by rheology, cryo-TEM, and SAXS.
• 16-4-16 MEA solutions behaved as elastic gels at 80 mmol L(−1).
• m-4-m MEA showed enhanced wormlike micelle formation compared to conventional Gemini surfactants.

Conclusions:

• The hydroxyl headgroup in m-4-m MEA surfactants promotes the formation of viscoelastic wormlike micelles.
• Synergistic interactions between hydrophobic attraction and hydrogen bonding drive the unique aggregation behavior.
• These findings contribute to understanding the impact of Gemini surfactant headgroup structure on aggregation in dilute solutions.