Understanding X-ray-induced isomerisation in photoswitchable surfactant assemblies

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Physical Chemistry

Background:

• Photosurfactants (PS) self-assemble into ordered nanostructures like micelles.
• Photoswitchable groups (azobenzene, arylazopyrazoles) enable dynamic material responses via photoisomerization.
• Small-angle X-ray scattering (SAXS) probes PS morphology and structural changes during in-situ light irradiation.

Purpose of the Study:

• Investigate the impact of X-ray irradiation on photosurfactant micelles.
• Determine if X-ray irradiation affects azobenzene (Azo) and arylazopyrazole (AAP) photoswitches differently.
• Provide guidelines for accurate SAXS experiments with photoswitchable molecules.

Main Methods:

• Utilized small-angle X-ray scattering (SAXS) with in-situ light irradiation.
• Examined micelles formed from two distinct photosurfactants: one with an Azo photoswitch, another with an AAP photoswitch.
• Analyzed the influence of X-ray and light irradiation on the photostationary state of the photoswitches.

Main Results:

• X-ray irradiation can induce unwanted Z-to-E isomerization in Azo-PS, affecting photostationary state measurements.
• The effect of X-ray irradiation on the Z isomer is dependent on the specific photoswitch, solvent, concentration, and morphology.
• Demonstrated that X-ray-induced isomerization varies between Azo and AAP photoswitches.

Conclusions:

• Established that X-ray irradiation can interfere with SAXS studies of photoswitchable materials.
• Developed recommendations for conducting SAXS experiments to minimize X-ray-induced artifacts.
• Aimed to improve the accuracy of understanding photosurfactant behavior for applications in energy storage, catalysis, and drug delivery.