Tough, Stretchable, and Thermoresponsive Smart Hydrogels

Area of Science:

• Materials Science
• Polymer Chemistry

Background:

• Hydrogels are crucial in various applications but often lack self-healing and robust mechanical properties.
• Thermoresponsive materials offer dynamic responses to temperature changes.
• Triple network (TN) hydrogels enhance mechanical strength and resilience.

Purpose of the Study:

• To develop self-healing, thermoresponsive triple network (TN) hydrogels.
• To investigate the effect of tannic acid (TA) concentration on hydrogel properties.
• To evaluate the mechanical performance, self-healing efficiency, and thermal responsiveness of the developed TN hydrogels.

Main Methods:

• Copolymerization of N-isopropyl acryl amide (NiPAAm) with functionalized polyvinyl alcohol (PVA) and N,N'-methylene bis(acryl amide) crosslinker.
• Incorporation of low concentrations of tannic acid (TA) (<1 wt.%).
• Freeze-thaw crystallization of PVA, X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), tensile testing, step-sweep strain tests, and swelling-deswelling loop tests.

Main Results:

• TN hydrogels with varying TA concentrations were successfully synthesized.
• Higher TA concentrations reduced PVA crystallinity and crystal size.
• A gel with 0.5 wt.% TA demonstrated high elongation at break (880%), excellent self-healing efficiency (81%), thixotropic behavior, good thermal responsiveness (swelling ratio of 13.3), and enhanced dimensional robustness.

Conclusions:

• Tannic acid effectively enhances the self-healing, mechanical, and thixotropic properties of TN hydrogels.
• The developed TN hydrogels exhibit a promising balance of mechanical strength, self-healing ability, and thermal responsiveness.
• These materials show potential for applications requiring dynamic and resilient soft materials.