Fluorescent hydrogels with tunable nanostructure and viscoelasticity for formaldehyde removal

Area of Science:

• Materials Science
• Polymer Chemistry
• Supramolecular Chemistry

Background:

• Hydrogels with high water content and mechanical strength are desirable for various applications.
• The self-assembly of molecules and their response to external stimuli are key areas of materials research.
• Controlling hydrogel properties through chemical composition and environmental factors is crucial for their development.

Purpose of the Study:

• To synthesize and characterize ultrahigh water content hydrogels with excellent mechanical strength using 4 -para-phenylcarboxyl-2,2 :6 ,2″-terpyridine (PPCT).
• To investigate the influence of cation hydration radius on the gelation process in PPCT/MOH systems.
• To explore the stimuli-responsive properties and formaldehyde adsorption capabilities of the developed hydrogels.

Main Methods:

• Preparation of hydrogels by mixing PPCT in aqueous KOH solutions.
• Rheological measurements to study self-assembled structure and gel-sol transformation temperature (Tgel-sol).
• Systematic variation of cation type (e.g., Li+, Na+, K+, Cs+) to determine the effect on gelation.

Main Results:

• Successfully prepared hydrogels with approximately 99 wt% water content and high mechanical strength.
• Demonstrated that cation hydration radius (Rh) within a specific range (3.29–3.58 Å) is critical for PPCT hydrogel formation, following the Hofmeister series.
• Observed stimuli-responsive behavior (temperature, shear force) and enhanced fluorescence upon gelation, with potential for self-healing.
• Showcased efficient formaldehyde (HCHO) adsorption and conversion into non-toxic salts.

Conclusions:

• PPCT/KOH hydrogels offer easily controllable synthesis conditions and tunable properties based on component concentrations.
• The Hofmeister series and cation hydration radius are vital parameters for designing PPCT-based hydrogels.
• These hydrogels are promising candidates for self-healing materials and effective formaldehyde removal from indoor environments.