A facile method to fabricate hybrid hydrogels with mechanical toughness using a novel multifunctional cross-linker

Abstract

Introducing both chemical and physical cross-links into a polymer network has emerged as a prevalent strategy to toughen hydrogels. However, most of these hybrid hydrogels are prepared in a multi-step route with more than one polymer or cross-linker, which is sophisticated and time consuming. Here, we report on a facile fabrication by in situ polymerization of acrylamide with a single multifunctional cross-linker. Compressive and tensile tests show the obtained hydrogels exhibit superior mechanical toughness. They can be stretched up to 1900% with a maximal fracture stress of nearly 500 kPa and be compressed by 90%. More impressively, the hydrogels can be fully recovered under compression. Rheological measurements suggest the co-existence of physical and chemical cross-links. Finally, an effective energy dissipation mechanism is observed and discussed. We conclude that the reversible physical cross-links originated from entanglement provide a mechanism of energy dissipation while the chemical cross-links ensure the structural integrity, which could be responsible for the improved mechanical properties.