Polyimides with Excited-State Intramolecular Proton Transfer and Room-Temperature Phosphorescence Properties by...

Area of Science:

• Organic Chemistry
• Materials Science
• Photophysics

Background:

• Organic polymers with excited-state intramolecular proton transfer (ESIPT) display unique photoluminescence, including large Stokes shifts and environmental sensitivity.
• Stimulus-responsive materials are crucial for advanced optical and electronic applications.

Purpose of the Study:

• To design and synthesize novel polyimides (PIs) integrating both ESIPT and room-temperature phosphorescence (RTP) properties.
• To investigate the photophysical behavior and stimulus-responsive characteristics of these new polyimides.

Main Methods:

• Synthesis of polyimides end-capped with 5-amino-2-(2-hydroxyphenyl) benzothiazole (HBTA) and 5-amino-2-(2-hydroxyphenyl) benzimidazole (HBIA).
• Characterization of photoluminescence (fluorescence and phosphorescence) properties, including quantum yields and decay lifetimes.
• Theoretical calculations to understand the role of spin-orbit coupling (SOC) and intersystem crossing (ISC) in phosphorescence emission.

Main Results:

• HBTA-PI and HBIA-PI demonstrated bright yellow-green and sky-blue fluorescence, respectively, with high photoluminescence quantum yields.
• Both polyimides exhibited strong room-temperature phosphorescence (RTP) with significant decay lifetimes.
• The synthesized polyimides showed excellent ESIPT properties, enabling sensitive detection of HCl vapor with distinct color changes in both fluorescence and phosphorescence.

Conclusions:

• The designed polyimides effectively combine ESIPT and RTP, leading to enhanced photophysical properties.
• Rigid polyimide networks and strong SOC in keto forms contribute to efficient phosphorescence.
• These materials show promise as multi-stimulus responsive organic polymers for sensing applications.