Octanol-triggered self-assemblies of the CTAB/KBr system: a microstructural study

Area of Science:

• Colloid and Surface Science
• Materials Science
• Physical Chemistry

Background:

• Cetyltrimethylammonium bromide (CTAB) is a common cationic surfactant.
• Surfactant solutions can form various self-assembled structures like micelles and vesicles.
• Understanding these transitions is crucial for applications in materials science and nanotechnology.

Purpose of the Study:

• To investigate the micelle-vesicle transition in an aqueous CTAB/KBr system induced by n-octanol (C(8)OH).
• To characterize the morphological changes and their impact on the system's properties.
• To elucidate the role of n-octanol concentration in driving these transitions.

Main Methods:

• Viscometry
• Rheology
• Dynamic Light Scattering (DLS)
• Cryo-transmission Electron Microscopy (cryo-TEM)

Main Results:

• Four distinct regions (I-IV) of morphological transitions were identified with increasing C(8)OH concentration.
• At low C(8)OH, micelle size increased.
• Elongated micelles transitioned to entangled wormlike micelles (viscoelastic fluid), followed by transformation into vesicles around 0.020 M C(8)OH.
• Vesicles became the predominant structures at higher C(8)OH concentrations, exhibiting unusual temperature responses.

Conclusions:

• N-octanol effectively induces a micelle-to-vesicle transition in CTAB/KBr aqueous systems.
• The study provides a detailed characterization of the microstructural evolution and fluid behavior.
• The findings offer insights into self-assembly phenomena in surfactant systems and their potential applications.