Toward Self-Healing Hydrogels Using One-Pot Thiol-Ene Click and Borax-Diol Chemistry.

Area of Science:

• Materials Science
• Polymer Chemistry
• Biomaterials Engineering

Background:

• Self-healing hydrogels are crucial for medical applications but are often limited by complex preparation and high costs.
• Existing methods for creating self-healing hydrogels involve multistep synthesis and expensive precursors like tetra-polyethylene glycol.

Purpose of the Study:

• To develop a facile, cost-effective one-pot method for synthesizing self-healing polyethylene glycol (PEG) based hydrogels.
• To investigate the use of borax as a catalyst for thiol-ene Michael-type polyaddition in PEG gel formation.
• To characterize the properties and self-healing capabilities of the newly prepared PEG hydrogels.

Main Methods:

• A one-pot synthesis approach was employed using polyethylene glycol diacrylate and dithiothreitol.
• Borax was utilized as a catalyst for the thiol-ene Michael-type polyaddition reaction.
• Characterization included mechanical testing (storage modulus), self-healing assessment, and responsiveness to pH and temperature.

Main Results:

• Rapid gelation (40 seconds to 2 minutes) was achieved at room temperature using borax as a catalyst.
• Borax facilitated the simultaneous formation of covalent thioether and transient boronate ester bonds.
• The resulting PEG hydrogels demonstrated a storage modulus up to 10^4 Pa, comparable to permanently cross-linked gels.
• The hydrogels exhibited intrinsic self-healing within 30 minutes without external stimuli.
• The hydrogels were transparent and displayed pH and thermal responsiveness.

Conclusions:

• A novel, efficient, and economical method for preparing self-healing PEG hydrogels has been established using borax catalysis.
• The unique dual-bonding mechanism induced by borax results in robust mechanical properties and rapid self-healing.
• These versatile hydrogels hold significant potential for applications in areas such as gel sealants, biosensors, and regenerative medicine.