Waterborne Polyurethanes with Tunable Fluorescence and Room-Temperature Phosphorescence.

Area of Science:

• Materials Science
• Polymer Chemistry
• Photophysics

Background:

• Single-component materials exhibiting both fluorescence and room-temperature phosphorescence (RTP) are crucial for advanced applications like ratiometric sensing and imaging.
• Developing such dual-emissive materials requires precise control over molecular structure and intermolecular interactions.

Purpose of the Study:

• To synthesize and characterize novel single-component dual-emissive materials (SDMs) based on waterborne polyurethanes (WPU).
• To investigate the effect of chromophore concentration on the luminescence properties (fluorescence and RTP) of the SDMs.
• To elucidate the underlying mechanism responsible for the observed luminescence tuning.

Main Methods:

• Covalent incorporation of an amino-substituted benzophenone into a WPU matrix.
• Characterization of statistical, thermal, and optical properties of the resulting SDMs at varying aminobenzophenone concentrations.
• Theoretical calculations to examine the polymerization-enhanced intersystem crossing (PEX) mechanism.

Main Results:

• Successful synthesis of SDMs with tunable fluorescence and RTP emission.
• Observation that increasing aminobenzophenone concentration leads to a narrowed singlet-triplet energy gap.
• Experimental and theoretical evidence supporting the PEX mechanism, highlighting the role of K1 aggregates in enhancing singlet-to-triplet state transitions.

Conclusions:

• Amino-substituted benzophenone-based WPU systems serve as effective single-component dual-emissive materials.
• Polymerization-enhanced intersystem crossing (PEX) is a viable mechanism for tuning luminescence properties in polymeric systems.
• The concentration of luminophores significantly impacts excitonic coupling and intersystem crossing rates, offering a pathway for material design.