Fig. 2: Preparation and material properties of PVA hydrogels through sequential solvent substitution.
a Schematic illustration of the fabrication process, including freeze-thawing (FT), glycerol substitution (GS), and ionic substitution (IS), leading to progressively enhanced hydrogel networks. b 1H-NMR spectra of FT, GS, and IS in DMSO-d6 at 295 K. c Tensile stress–strain curves of PVA hydrogels after different solvent substitution treatments, compared to the range of human skin (orange shaded region). d Toughness and stiffness of the hydrogels across different treatments. e Schematic of the mechanical enhancement mechanism involving dense crystalline and ionic crystalline regions. f DSC thermograms of FT, GS, and IS. g XRD profiles of FT, GS, and IS. h WAXS patterns showing the crystallinity evolution among FT, GS, and IS. i Synchronized and asynchronized 2D-COS maps of FT, GS, and IS, where red and blue indicate positive and negative intensity, respectively. j Comparison of hydrogel toughness achieved in this study with that of various reported hydrogels and biological tissues.
