Buckled membranes in mixed-valence ionic amphiphile vesicles

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Physical Chemistry

Background:

• Amphiphilic molecules self-assemble into various structures driven by intermolecular forces.
• Supramolecular shape is fundamentally determined by the balance of attractive and repulsive interactions.
• Electrostatic, hydrophobic, and steric forces play crucial roles in dictating self-assembled morphologies.

Purpose of the Study:

• To investigate the co-assembly of anionic and cationic amphiphiles with unequal charges.
• To explain the formation of non-spherical, specifically buckled, vesicle structures.
• To present a physical model for the observed buckled vesicle morphology.

Main Methods:

• Co-assembly of anionic and cationic amphiphiles with differing charge magnitudes.
• Experimental observation and characterization of self-assembled structures.
• Theoretical and physical argument to explain the observed morphology.

Main Results:

• Anionic and cationic amphiphiles of unequal charge co-assemble into small buckled vesicles.
• Strong electrostatic interactions between +3 and -1 charged head groups enhance cohesion.
• Formation of two-dimensional, flat ionic domains on the vesicle surface leads to buckled shapes.

Conclusions:

• Unequal charge distribution in co-assembling amphiphiles is a key factor in generating non-spherical supramolecular structures.
• The interplay of electrostatic forces, particularly strong attractions between oppositely charged head groups, drives the formation of buckled vesicles.
• This study provides a physical basis for understanding the formation of complex self-assembled shapes from simple molecular building blocks.