Thermal- and salt-activated shape memory hydrogels based on a gelatin/polyacrylamide double network

Area of Science:

• Materials Science
• Polymer Chemistry
• Biomaterials

Background:

• Shape memory hydrogels are crucial for various applications due to their adaptive properties.
• Developing hydrogels with tunable shape memory effects is an active area of research.
• Biopolymer-based materials offer biocompatibility and unique functionalities.

Purpose of the Study:

• To develop a gelatin/polyacrylamide double network hydrogel with dual thermal and salt-activated shape memory capabilities.
• To elucidate the mechanisms behind the thermal and salt-induced shape memory effects.
• To evaluate the shape fixity and recovery performance of the novel hydrogel.

Main Methods:

• Fabrication of a double network hydrogel using gelatin and polyacrylamide.
• Investigation of shape memory behavior triggered by temperature changes (cooling/heating).
• Assessment of salt-induced shape memory effects using ammonium sulfate ((NH4)2SO4) and deionized water for ion removal.
• Characterization of hydrogel properties, including shape fixity and recovery ratio.

Main Results:

• The hydrogel successfully memorized temporary shapes induced by cooling or salt immersion.
• Shape recovery was achieved by heating or washing out the salt ions.
• The thermally activated shape memory effect is linked to gelatin's triple helix transformation.
• The salt-activated effect is attributed to hydrophobic interactions influenced by the Hofmeister effect.
• The hydrogel demonstrated excellent shape fixity and recovery ratios.

Conclusions:

• A novel biopolymer-based shape memory hydrogel with dual thermal and salt responsiveness was successfully developed.
• The study provides insights into the mechanisms governing dual-responsive shape memory behavior in hydrogels.
• This work expands the potential applications of biopolymer-based shape memory hydrogels in smart materials and devices.