Imidazolidinyl urea reinforced polyacrylamide hydrogels through the formation of multiple hydrogen bonds

Hydrogels with outstanding mechanical characteristics, remoldability, and self-healability possess vast potentials in biomedical applications and flexible sensors. However, it is still difficult to prepare hydrogels with integrated mechanical characteristics straightforwardly. Herein, we proposed to introduce a hydrogen bonding reinforced factor, imidazolidinyl urea (IU), to the polymerization of acrylamide for the construction of multi-functional hydrogels in one pot. There are multiple hydrogen bonding donors and receptors in IU, which can interact with polyacrylamide through multiple hydrogen bonds to form the hydrogel networks. The break strength, fracture elongation, and compressive strength of the IU-included hydrogels could be adjusted in the range of 18.8–23.8 kPa, 305%–560%, and 2.0–3.9 MPa, respectively. The hydrogels featured outstanding fatigue resistance, and the obvious loss of compressive strength was not observed even after 50 cycles of loading-unloading under 85% strain. Moreover, the IU-based hydrogels not only showed promising self-healing and remodeling abilities but also exhibited nonconventional emission behaviors. Our work offers a facile strategy for the construction of multi‑hydrogen bond crosslinked hydrogels and may inspire researchers to explore new supramolecular systems using the hydrogen bonding reinforced factor (IU).