Surface-Relief Gratings in Halogen-Bonded Polymer-Azobenzene Complexes: A Concentration-Dependence Study

Area of Science:

• Materials Science
• Polymer Chemistry
• Photophysics

Background:

• Supramolecular complexes of poly(4-vinylpyridine) and azobenzene derivatives are used for light-induced surface-relief gratings (SRGs).
• Previous research focused on optimizing polymer-azobenzene interactions with low azobenzene content.
• The concentration dependence of SRG formation in these systems remains largely unexplored.

Purpose of the Study:

• To investigate the effect of azobenzene concentration on SRG formation in halogen-bonded polymer-azobenzene complexes.
• To explore SRG inscription across a wide range of azobenzene content, from 10 mol% to equimolar.

Main Methods:

• Utilized two distinct halogen-bond-donating azobenzene derivatives with tetrafluoroiodophenyl and iodoethynylphenyl groups.
• Prepared complexes as spin-coated thin films.
• Analyzed SRG formation using optical microscopy, atomic force microscopy, and optical diffraction.

Main Results:

• Achieved high diffraction efficiencies up to 35%.
• Obtained modulation depths approaching 400 nm.
• Demonstrated significantly improved SRG performance compared to previously reported halogen-bonded systems.

Conclusions:

• Azobenzene concentration is a critical factor in optimizing SRG formation in these supramolecular complexes.
• High azobenzene content leads to substantially enhanced surface patterning capabilities.
• These findings pave the way for advanced photoresponsive materials with improved performance.