Novel mesogenic azobenzene dimer at air-water and air-solid interfaces

Area of Science:

• Materials Science
• Supramolecular Chemistry
• Organic Electronics

Background:

• Azobenzene derivatives are known for their photoresponsive properties.
• Mesogenic molecules form ordered liquid crystal phases.
• Langmuir and Langmuir-Blodgett techniques are crucial for studying thin films.

Purpose of the Study:

• Synthesize and characterize a novel H-shaped azobenzene dimer (12D1H).
• Investigate the monolayer film properties at the air-water and air-solid interfaces.
• Explore the effect of UV light on the azobenzene molecule and its film stability.

Main Methods:

• Synthesis of the 12D1H molecule.
• Surface manometry for air-water interface studies.
• Brewster angle microscopy (BAM) for domain observation.
• Atomic force microscopy (AFM) for film morphology on mica and silicon substrates.
• UV-Vis spectroscopy for photoisomerization studies.

Main Results:

• The 12D1H molecule exhibits a smectic C liquid crystal phase.
• Stable Langmuir monolayers were formed at the air-water interface.
• AFM confirmed monomolecular film formation on mica and nanodroplet formation via spinodal dewetting on silicon.
• UV light induced trans-cis isomerization, significantly increasing monolayer stability and collapse pressure.

Conclusions:

• The novel H-shaped azobenzene dimer (12D1H) forms stable monolayers with distinct morphologies depending on the substrate.
• Photoisomerization of the azobenzene unit enhances film stability, suggesting potential applications in photoresponsive devices.
• The study provides insights into the self-assembly behavior and interfacial properties of novel mesogenic azobenzene materials.