Knoevenagel Condensation Reaction-Empowered Hydrogels with pH-Tunable Dynamic Properties

Area of Science:

• Materials Science
• Polymer Chemistry
• Biomedical Engineering

Background:

• Dynamic hydrogels offer unique properties like self-healing for biomedical applications.
• Controlling hydrogel dynamics is crucial for tailoring their performance.

Purpose of the Study:

• To develop a novel hydrogel with pH-tunable dynamic properties.
• To investigate the Knoevenagel condensation (KC) reaction for creating dynamic hydrogels.

Main Methods:

• Utilized the reversible Knoevenagel condensation (KC) reaction to form dynamic C═C bonds in hydrogels.
• Modulated pH to control the association rate constant (k1), dissociation rate constant (k-1), and equilibrium constant (Keq) of the KC reaction.
• Measured changes in relaxation time (τ1/2), structural stability, and mechanical performance across a pH range of 10 to 1.

Main Results:

• Decreasing pH from 10 to 1 progressively increased the relaxation time (τ1/2) from 100 to over 1,000 s.
• pH reduction decelerated KC reaction kinetics (k1 and k-1) while increasing Keq.
• Enhanced structural stability and improved mechanical performance were observed at lower pH values.

Conclusions:

• The Knoevenagel condensation (KC) reaction provides a viable strategy for creating pH-responsive dynamic hydrogels.
• Tunable dynamic properties of hydrogels can be achieved by controlling KC reaction kinetics via pH modulation.
• This approach offers a new pathway for designing advanced hydrogels with tailored properties for biomedical applications.