pH-Switchable and self-healable hydrogels based on ketone type acylhydrazone dynamic covalent bonds

Area of Science:

• Polymer Chemistry
• Materials Science
• Biomedical Engineering

Background:

• Stimuli-responsive hydrogels combine physical gel properties with chemical gel stability using dynamic covalent bonds (DCBs).
• Ketone-based polymers offer a route to novel DCB hydrogels with tunable characteristics.
• Existing DCB hydrogels may have limitations in biocompatibility due to specific chemical components.

Purpose of the Study:

• To synthesize and characterize novel ketone-based hydrogels using dynamic covalent bonds.
• To investigate the influence of polymer composition on hydrogel properties, including mechanics and self-healing.
• To evaluate the pH-responsive behavior and controlled release capabilities of the developed hydrogels.

Main Methods:

• Synthesis of ketone-based polymers via reversible addition-fragmentation chain transfer (RAFT) polymerization using diacetone acrylamide (DAAM).
• Hydrogel formation through the reaction of DAAM-based polymers with hexanedihydrazide.
• Characterization of hydrogel mechanics, self-healing, sol-gel transitions, and controlled release properties.

Main Results:

• Tunable hydrogel mechanics and properties were achieved by varying the DAAM ratio.
• The hydrogels exhibited spontaneous self-healing and switchable pH-responsive sol-gel transitions.
• Controlled release of rhodamine B was demonstrated, influenced by pH changes.
• Ketone-type acylhydrazone DCB hydrogels, free of aldehydes, were successfully prepared.

Conclusions:

• Ketone-based acylhydrazone DCB hydrogels offer a promising platform for stimuli-responsive materials.
• The tunable nature and self-healing properties make them suitable for advanced applications.
• Avoiding aldehyde components may enhance biocompatibility for potential use in biomedicine and tissue engineering.