Photoresponsive Self-Assembly of Surface Active Ionic Liquid.

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Physical Chemistry

Background:

• Surface active ionic liquids (SAILs) are versatile molecules with tunable properties.
• Controlling self-assembly and material properties with external stimuli is a key challenge in materials science.
• Photoresponsive materials offer precise control over structural changes.

Purpose of the Study:

• To design and synthesize a novel photoresponsive SAIL ([C14mimAzo]Br) incorporating an azobenzene moiety in the headgroup.
• To investigate the light-induced reversible vesicle formation and rupture in aqueous solutions of the SAIL.
• To elucidate the mechanism behind photoresponsive self-assembly using spectroscopic and computational methods.

Main Methods:

• Synthesis of 1-(4-methyl azobenzene)-3-tetradecylimidazolium bromide ([C14mimAzo]Br).
• Photoisomerization studies using (1)H NMR and UV-vis spectroscopy.
• Density Functional Theory (DFT) calculations to understand aggregation behavior and energetics.
• Observation of vesicle formation and rupture under photostimuli.

Main Results:

• The synthesized [C14mimAzo]Br exhibits reversible trans-cis photoisomerization upon light irradiation.
• Vesicle formation is favored by the trans-isomer due to increased hydrophobicity and reduced electrostatic repulsion.
• Vesicle rupture is induced by the cis-isomer, which hinders tight aggregation.
• Controlled vesicle dynamics were achieved without external additives.

Conclusions:

• A novel photoresponsive SAIL ([C14mimAzo]Br) was successfully developed.
• Photostimuli enable precise control over vesicle formation and rupture in aqueous SAIL solutions.
• The azobenzene unit's photoisomerization is key to controlling self-assembly and material topology.
• This work provides a facile method for achieving tunable self-assembly in single SAIL systems.