Mechanically robust, notch-insensitive, fatigue resistant and self-recoverable hydrogels with homogeneous and viscoelastic network constructed by a novel multifunctional cross-linker

Abstract

Designing a homogeneous network is an efficient way to improve the mechanical properties of hydrogels. However, the homogeneous hydrogels usually have negligible notch-insensitivity due to the lack of effective energy dissipation, limiting their practical applications in many fields. Herein, we provide a straightforward method to prepare a category of tough and notch-insensitive polyacrylamide hydrogels crosslinked by a novel cross-linker with multiple vinyl functional groups (TA). Due to the multifunctionality of TA, a relatively uniform network with the coexistence of physical cross-links is constructed by the steric effect between chain radicals on TA molecules during the polymerization. The uniform network distributes stress evenly while the physical cross-links lead to viscoelastic dissipated energy under external force. As a result, the hydrogels achieve an ultrastretchability of 2400% and a tensile toughness of 4.33 MJ/m3. Even with a notch of 10 mm, the hydrogels can still be stretched to a strain of 20, indicating an impressive notch-insensitivity. Meanwhile, the hydrogels exhibit high fatigue resistance and good self-recovery. This research offers a facile strategy for designing high-performance hydrogels and may pave the way for their practical application in emerging fields, such as oil displacement agent and artificial cartilage.