Harnessing Chain Mobility via Protonation for Tough and Isotropic Hydrogel

Area of Science:

• Materials Science
• Polymer Chemistry
• Biomaterials Engineering

Background:

• Fabricating hydrogels with isotropic high tensile strength, stretchability, and toughness is critical for tissue engineering, stretchable bioelectronics, and soft robotics.
• Existing toughening strategies often induce anisotropy or fail to simultaneously enhance all desired mechanical properties.

Purpose of the Study:

• To develop a strategy for fabricating ultra-tough, isotropic poly(vinyl alcohol) (PVA) hydrogels.
• To synergistically modulate polymer chain mobility and physical crosslinking for enhanced hydrogel properties.

Main Methods:

• Sequential acidification to suppress premature hydrogen bonding and homogenize the network.
• Freeze-thawing and salting-out processes to strengthen interpolymer hydrogen bonds and form crystalline physical crosslinks.
• Characterization of mechanical properties including tensile strength, stretchability, and toughness.

Main Results:

• Achieved a high tensile strength of 29.5 MPa and stretchability of 2683%.
• Obtained a record-high toughness of 424 MJ m⁻³ for isotropic hydrogels, surpassing some anisotropic hydrogels.
• Demonstrated isotropic mechanical properties superior to existing methods.

Conclusions:

• The developed strategy provides a generalizable platform for engineering tough, isotropic hydrogels.
• The resulting PVA hydrogels exhibit exceptional mechanical performance for diverse applications.
• This approach holds significant potential for bioengineering, additive manufacturing, and soft robotics.