Micellar dipole potential is sensitive to sphere-to-rod transition

Area of Science:

• Colloid and Surface Science
• Physical Chemistry
• Biophysical Chemistry

Background:

• Structural transitions in charged micelles are crucial for cellular physiology.
• Increasing ionic strength is a common method to induce these transitions.
• Micellar dipole potential is a key property influenced by micellar structure.

Purpose of the Study:

• To investigate the sphere-to-rod transition in charged micelles (SDS and CTAB).
• To monitor changes in micellar dipole potential during these transitions.
• To understand the relationship between micellar structure, shape, and dipole potential.

Main Methods:

• Utilizing charged micelles of sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB).
• Inducing sphere-to-rod transitions by increasing ionic strength.
• Measuring micellar dipole potential using the dual wavelength ratiometric approach with di-8-ANEPPS.

Main Results:

• Micellar dipole potential increases with increasing ionic strength, regardless of micelle charge.
• The sphere-to-rod transition is sensitive to changes in micellar dipole potential.
• Dipolar reorganization, due to confined dipoles, underlies the observed potential changes.

Conclusions:

• Micellar dipole potential is a sensitive indicator of structural transitions and shape changes.
• Sphere-to-rod transitions involve significant dipolar reorganization at the micelle interface.
• Dipole potential measurements offer novel insights into micellar processes involving dipolar reorganization.