Self-healing hydrogels containing reversible oxime crosslinks.

Area of Science:

• Polymer Chemistry
• Materials Science
• Supramolecular Chemistry

Background:

• Hydrogels are versatile polymeric networks with applications in drug delivery, tissue engineering, and soft robotics.
• Developing stimuli-responsive hydrogels that can reversibly transition between gel and sol states is crucial for advanced material design.
• Dynamic covalent chemistry, particularly oxime exchange, offers a promising route for creating self-healing and responsive materials.

Purpose of the Study:

• To develop novel oxime-functional hydrogels capable of reversible gel-to-sol transitions.
• To investigate the chemo-responsive and thermo-responsive properties of these hydrogels.
• To explore the self-healing capabilities arising from dynamic oxime crosslinks.

Main Methods:

• Synthesis of keto-functional copolymers (P(DMA-stat-DAA)) via radical polymerization of N,N-dimethylacrylamide (DMA) and diacetone acrylamide (DAA).
• Chemical crosslinking of copolymers with difunctional alkoxyamines to form oxime-based hydrogels.
• Induction of gel-to-sol transitions using excess monofunctional alkoxyamines under acidic conditions (25 °C).
• Characterization of thermo-responsive behavior and cloud points of copolymers with varying DAA content.

Main Results:

• Successfully synthesized self-healing oxime-functional hydrogels.
• Demonstrated reversible gel-to-sol transitions triggered by acidic conditions and competitive oxime exchange.
• Observed autonomous self-healing of damaged hydrogels due to dynamic oxime crosslinks.
• Confirmed chemo-responsive behavior and tunable thermo-responsive properties (cloud points) based on DAA content.
• Formed both dynamic-covalent and physically-crosslinked gels exhibiting reversible gelation.

Conclusions:

• Oxime-functional hydrogels offer a robust platform for creating self-healing and stimuli-responsive materials.
• The developed hydrogels exhibit dual chemo- and thermo-responsive behavior, enabling tunable gelation.
• The dynamic nature of oxime crosslinks is key to achieving autonomous healing and reversible transitions.
• These materials hold potential for applications requiring adaptable and repairable soft materials.