Halogenated azobenzene acrylates: from efficient solution photoswitching to stable solid-state photochromic materials

Area of Science:

• Materials Science
• Organic Chemistry
• Photochemistry

Background:

• Azobenzene derivatives are widely studied for photoresponsive applications.
• Tuning material properties through chemical modification is crucial for advanced functionalities.
• Halogen substituents offer a potential route to modulate azobenzene behavior.

Purpose of the Study:

• To design, synthesize, and characterize novel halogenated azobenzene acrylate monomers.
• To investigate the impact of fluorine, chlorine, and bromine substituents on material properties.
• To explore the potential of these monomers in photoresponsive systems.

Main Methods:

• A three-step synthetic route involving azo-coupling, O-alkylation, and O-acylation.
• Comprehensive characterization of synthesized monomers using various analytical techniques.
• Evaluation of photoresponsive behavior, including E → Z photoconversion efficiency and stability.

Main Results:

• Six novel halogenated azobenzene acrylate monomers were successfully synthesized.
• Halogen substitution significantly tuned thermal, optical, and light-induced switching properties.
• Monohalogen derivatives showed high E → Z photoconversion efficiency (up to 93%).
• The difluoro derivative's Z-isomer exhibited notable thermal stability.
• A monofluoro derivative in a polystyrene film maintained color change for over 90 days.

Conclusions:

• Ortho-halogenation is an effective strategy for tuning photoresponsive material properties.
• These novel monomers show promise for applications in colorimetric thermal sensing.
• The developed materials are suitable for light-controlled functional systems.