A phenol-induced structural transition in aqueous cetyltrimethylammonium bromide solution

Area of Science:

• Physical Chemistry
• Materials Science
• Colloid Science

Background:

• Cetyltrimethylammonium bromide (CTAB) is a widely used cationic surfactant.
• Understanding surfactant micelle behavior is crucial for various applications.
• Phenol's interaction with surfactant systems can modify their properties.

Purpose of the Study:

• To investigate the structural changes in CTAB micelles upon phenol addition.
• To elucidate the mechanism of phenol solubilization within CTAB micelles.
• To correlate structural modifications with changes in solution properties.

Main Methods:

• Viscosity measurements
• Dynamic Light Scattering (DLS) for hydrodynamic diameter
• Small Angle Neutron Scattering (SANS) for micelle shape and size
• Nuclear Magnetic Resonance (NMR) for molecular interactions

Main Results:

• Viscosity and micelle hydrodynamic diameter initially increase then decrease with phenol addition.
• SANS reveals a prolate ellipsoidal micelle structure, with axial ratio changes mirroring viscosity and DLS data.
• NMR confirms phenol solubilization in the palisade layer and micelle growth at higher phenol concentrations.

Conclusions:

• Phenol significantly influences CTAB micelle structure and dynamics.
• The observed changes are attributed to phenol's incorporation into the micelle palisade layer.
• This study provides insights into surfactant-phenol interactions and micellar system modifications.