Multiple hydrogen-bonding induced nonconventional red fluorescence emission in hydrogels

Area of Science:

• Materials Science
• Polymer Chemistry
• Supramolecular Chemistry

Background:

• Developing long-wavelength fluorescent polymer hydrogels without polycyclic aromatic hydrocarbons or extended π-conjugation presents a significant challenge.
• Understanding spatial interactions driving clustering-triggered emission in water-rich conditions is crucial for luminescent materials.

Purpose of the Study:

• To propose a thermodynamically driven strategy for creating red fluorescence in polymer hydrogels.
• To investigate the mechanism of fluorescence shifts from blue to red via clustering-triggered emission.

Main Methods:

• Boiling multiple hydrogen-bonded poly(N-acryloylsemicarbazide) hydrogels in a water bath.
• Analyzing thermodynamically driven conformational changes in polymer chains.
• Characterizing fluorescence properties, stability, mechanical robustness, and 3D printability.

Main Results:

• Achieved red fluorescence (~610 nm) through a heat-induced, thermodynamically driven process.
• Demonstrated that conformational changes from isolated hydrogen bonding to through-space interactions induce fluorescence shifts.
• The resulting hydrogels exhibit good fluorescence stability, mechanical strength, and 3D printability.

Conclusions:

• A viable method for preparing nonconventional long-wavelength fluorescent hydrogels without pre-existing fluorescent components was established.
• The study provides insights into clustering-triggered emission mechanisms in water-rich environments.
• The developed hydrogels are suitable for soft fluorescent devices and customizable shaping.