Strong and Ultra-tough Ionic Hydrogel Based on Hyperbranched Macro-Cross-linker: Influence of Topological Structure on Properties

The application of hydrogels often suffers from their inherent limitation of poor mechanical properties. Here, a carboxyl-functionalized and acryloyl-terminated hyperbranched polycaprolactone (PCL) was synthesized and used as a macro-cross-linker to fabricate a super strong and ultra-tough ionic hydrogel. The terminal acryloyl groups of hyperbranched PCL are chemically incorporated into the network to form covalent cross-links, which contribute to robust networks. Meanwhile, the hydrophobic domains formed by the spontaneous aggregation of PCL chains and coordination bonds between Fe3+ and COO- groups serve as dynamic non-covalent cross-links, which enhance the energy dissipation ability. Especially, the influence of the hyperbranched topological structure of PCL on hydrogel properties has been well investigated, exhibiting superior strengthening and toughening effects compared to the linear one. Moreover, the hyperbranched PCL cross-linker also endowed the ionic hydrogel with higher sensitivity than the linear one when used as a strain sensor. As a result, this well-designed ionic hydrogel possesses high mechanical strength, superior toughness, and well ionic conductivity, exhibiting potential applications in the field of flexible strain sensors. A hyperbranched PCL was used as a macro-cross-linker to fabricate a novel family of strong and ultra-tough ionic hydrogels. By tailoring the hyperbranched topological structure, the optimal balance of covalent/non-covalent cross-linking could be obtained. As a result, the well-designed hydrogel possesses high strength, superior toughness, and good ionic conductivity, with potential applications in the field of flexible strain sensors.+image

Automated summary

A novel family of strong and ultra-tough ionic hydrogels was fabricated using a carboxyl-functionalized and acryloyl-terminated hyperbranched polycaprolactone (PCL) as a macro-cross-linker. The hydrogels exhibited high mechanical strength, superior toughness, and good ionic conductivity, making them suitable for flexible strain sensors. The hyperbranched PCL structure played a crucial role in enhancing the hydrogel properties, providing an optimal balance of covalent and non-covalent cross-linking.