Rapid gelation of polyacrylic acids-like hydrogel via the dopamine acrylamide-Fe³⁺ system and its formation mechanism

Tissue-like hydrogels with adjustable functionality have garnered significant attention in the medical, engineering, and flexible electronics fields. However, the preparation of hydrogels is often time-sconsuming and requires additional energy input. In this study, catechol-functionalized acrylamide (dopamine acrylamide, DAM) is firstly used in conjunction with Fe3+ to constitute a simple, efficient, universal and environmental tolerance catalytic system. The catalytic mechanism is thoroughly investigated through ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), electron spin-resonance (ESR) spectra, and density functional theory (DFT) calculations. The p(acrylic acid-dopamine acrylamide)/Fe3+/polyvinyl alcohol/SiO2 (PFPS) hydrogel is rapidly prepared without external energy within 20 s via DAM-Fe3+ system and exhibite outstanding stretchability (>1000 % strain), adhesion, self-healing properties. Sensitive, repeatable, and stable electrical signals with strain are detected by the PFPS hydrogel, indicating considerable potential in next-generation flexible strain sensors for exercise tracking and health management.