Aggregation-Induced Emission Rotors: Rational Design and Tunable Stimuli Response

Area of Science:

• Materials Science
• Organic Chemistry
• Photochemistry

Background:

• Aggregation-induced emission (AIE) materials exhibit enhanced luminescence upon aggregation.
• Tuning the stimuli response of AIE materials is crucial for advanced applications.
• Understanding the mechanism of AIE, particularly the role of intramolecular rotations, is an ongoing area of research.

Purpose of the Study:

• To develop a novel molecular design strategy for tuning the stimuli response of AIE materials.
• To investigate the relationship between molecular structure, specifically the number of tetraphenylethene (TPE) moieties, and the sensitivity of AIE rotors to viscosity and temperature.
• To gain deeper insights into the AIE mechanism, focusing on the restriction of intramolecular rotations (RIR).

Main Methods:

• Synthesis of a series of AIE-active molecules (AIE rotors) by covalently linking varying numbers of tetraphenylethene (TPE) units.
• Experimental characterization of the synthesized AIE rotors to evaluate their luminescent properties.
• Systematic investigation of the response of these AIE rotors to changes in viscosity and temperature.

Main Results:

• Increasing the number of rotatable phenyl rings in the TPE units significantly enhances the sensitivity of AIE rotors to viscosity and temperature.
• Larger molecular size, while increasing rotational barriers, led to only slight performance improvements due to a modest increase in effective rotors.
• The AIE rotor with the largest molecular size demonstrated the highest viscosity sensitivity, achieving a viscosity factor of 0.98.

Conclusions:

• A rational molecular design strategy effectively tunes the stimuli response of AIE materials.
• The study provides valuable insights into the AIE mechanism, highlighting the importance of restricted intramolecular rotations.
• The developed AIE rotors show potential as highly sensitive luminogens for viscosity sensing applications.