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

Area of Science:

• Colloid and Surface Science
• Rheology
• Supramolecular Chemistry

Background:

• Wormlike micelles are key self-assembled structures in surfactant solutions.
• Gemini surfactants offer unique properties due to their dual hydrophobic chains and head groups.
• Understanding mixed surfactant systems is crucial for designing advanced materials.

Purpose of the Study:

• To investigate the formation and properties of wormlike micelles in mixed cationic and anionic gemini surfactant systems.
• To compare the micellar behavior of a hydroxylated gemini surfactant (12-3(OH)-12) with its non-hydroxylated counterpart (12-3-12).
• To elucidate the role of hydrogen bonding and electrostatic interactions in micellar growth.

Main Methods:

• Steady-state and dynamic rheological measurements at 25°C.
• Preparation of aqueous solutions of mixed gemini surfactants: 12-3(OH)-12 and C(12)ϕC(12).
• Systematic variation of surfactant concentrations to study viscosity and micellar structure.

Main Results:

• The mixed system of 12-3(OH)-12 and C(12)ϕC(12) exhibited significantly enhanced solution viscosity compared to the 12-3-12/C(12)ϕC(12) system.
• Dynamic rheology indicated the formation of longer wormlike micelles in the 12-3(OH)-12/C(12)ϕC(12) system.
• Hydrogen bonding between 12-3(OH)-12 molecules was identified as a primary driver for increased micellar growth.

Conclusions:

• The hydroxyl group in the gemini surfactant plays a critical role in promoting wormlike micelle formation and growth via hydrogen bonding.
• Electrostatic attraction between oppositely charged head groups contributes to tighter packing and further enhances micellar growth.
• The findings provide insights into the design of novel surfactant systems with tailored rheological properties.