Phase behavior and microstructures in a mixture of anionic Gemini and cationic surfactants

Area of Science:

• Colloid and Surface Science
• Materials Science
• Physical Chemistry

Background:

• Understanding surfactant phase behavior is crucial for applications like drug delivery and enhanced oil recovery.
• Mixed surfactant systems offer tunable properties compared to single-component systems.

Purpose of the Study:

• To investigate the phase behavior and aggregate microstructures of a mixed system comprising an anionic Gemini surfactant (SDLC) and a cationic surfactant (DTAC).
• To correlate macroscopic phase transitions with microscopic structural evolution.

Main Methods:

• Rheology
• Dynamic Light Scattering (DLS)
• Transmission Electron Microscopy (TEM)
• Polarization Microscopy

Main Results:

• The SDLC-DTAC system transitions from an isotropic phase to an aqueous surfactant two-phase system (ASTP), and finally to an anisotropic phase with increasing DTAC concentration.
• Microstructures observed include linear wormlike micelles in the isotropic phase, branched wormlike micelles in the lower ASTP phase, vesicles in the upper ASTP phase, and lamellar liquid crystals in the anisotropic phase.

Conclusions:

• The study elucidates the relationship between macroscopic phase transitions and the evolution of microscopic aggregate structures in mixed surfactant systems.
• Findings contribute to understanding self-assembly mechanisms in complex surfactant formulations.