Phase-Transition-Induced Fluorescence Changes in a Calamitic Liquid Crystal With an AIEgen Mesogen

Area of Science:

• Materials Science
• Organic Chemistry
• Physical Chemistry

Background:

• Aggregation-induced emission (AIE) luminogens are known for environmental responsiveness.
• Combining AIE with liquid crystals offers potential for advanced multifunctional materials.
• This specific combination remains an underexplored area in materials science.

Purpose of the Study:

• To investigate the photophysical properties of a novel compound exhibiting both liquid crystal phases and AIE behavior.
• To understand the relationship between liquid crystalline phase transitions and AIE characteristics.
• To explore the potential of such materials as single-component, stimuli-responsive systems.

Main Methods:

• Synthesis and characterization of 3,8-bis(4-hexylphenyl)-6,7-dihydro-5H-benzo[7]annulene (DPB[7]-C6).
• Temperature-dependent fluorescence spectroscopy to monitor emission changes.
• Analysis of absorbance, fluorescence quantum yield, and orientational order as a function of temperature.

Main Results:

• DPB[7]-C6 exhibits both smectic A (SmA) and nematic (N) liquid crystal phases, alongside AIE.
• A distinct change in fluorescence intensity was observed at the SmA-N phase transition.
• The observed fluorescence change is attributed to variations in the quantum yield, influenced by the accessibility of the conical intersection (CI) in different liquid crystal phases.

Conclusions:

• A clear correlation exists between the morphology of liquid crystalline phases and the photophysical processes of AIE luminogens.
• The study highlights the potential of combining AIE and liquid crystals for developing single-component, stimuli-responsive materials.
• Understanding these structure-property relationships is crucial for designing next-generation functional materials.