Copper-Coordination Engineered Glassy Hydrogels Featuring Ultrastiffness and Structural Programmability

Area of Science:

• Materials Science
• Polymer Chemistry

Background:

• Glassy hydrogels offer potential for engineering applications but often lack sufficient strength, stiffness, and stability due to weak physical cross-linking.
• Existing materials struggle to meet demanding performance requirements in various technological fields.

Purpose of the Study:

• To engineer an ultrastiff and ultrastrong glassy hydrogel with improved mechanical properties and environmental stability.
• To explore the use of coordination bonds for creating robust hydrogel networks.
• To develop structurally programmable hydrogels with tunable properties.

Main Methods:

• A copper acetate-assisted strategy was employed to introduce coordination bonds into a polyacrylic acid (PAA) and polyvinyl alcohol (PVA) network.
• The alkaline environment generated by acetate anions facilitated deprotonation of PAA carboxyl groups, enabling coordination with copper ions.
• The formation of a densely cross-linked network in the glassy state was achieved through this coordination chemistry.

Main Results:

• The resulting glassy hydrogel demonstrated record-breaking Young's modulus (469.7 MPa) and tensile strength (19.2 MPa).
• Exceptional environmental stability was observed, surpassing conventional glassy hydrogels.
• Reversible softening and vitrification via coordination bond dynamics enabled the creation of an integrated auxetic hydrogel (IAH) with a negative Poisson's ratio.

Conclusions:

• The introduction of robust coordination bonds significantly enhances the mechanical properties and stability of glassy hydrogels.
• The developed hydrogel system offers a promising route for creating advanced materials with tunable and programmable characteristics.
• The integrated auxetic hydrogel exhibits superior mechanical performance and auxetic behavior, paving the way for novel functional materials.