Study on the mechanical properties of hydrogels enhanced by acryloyl‐functionalized polyethyleneimine cross‐links

Abstract Appropriate mechanical properties is one of the prerequisites for the applications of hydrogels, where cross‐linker is a crucial component in manipulating such mechanical property. Herein, acryloyl‐functionalized polyethyleneimine (APEI) was innovatively used as novel functional cross‐links to optimize the mechanical properties of polyacrylamide (PAM) hydrogels. APEI cross‐links were synthesized by simply adding acryloyl chloride into polyethyleneimine in aqueous solution. The chemical structures of APEI were confirmed by Fourier transform infrared and nuclear magnetic resonance spectra. APEI possessed massive highly acryloyl functional groups that can serve as multifunctional cross‐linking centers for the polymerization of monomers via covalent bonding interactions. These covalent bonds are favorable for constructing a firm 3D cross‐linked networks for hydrogels to withstand deformations, endowing hydrogels with the improved mechanical properties. The tensile strength with an elongation at break for the hydrogels can reach 234 kPa and 18.4‐fold, respectively. In addition, even the hydrogels can bear cyclic mechanical loads and deformations for 50 cycles at 5‐fold stain, indicating a good fatigue resistance. The deformability of APEI cross‐links clusters under stretching was responsible for the stretchability of PAM/APEI hydrogels. This work provides a simple strategy to enhance the mechanical properties of hydrogels via the development of novel APEI chemical cross‐linker.