Fig. 4. (a) Photographs of the gelatin/PAM hydrogels after immersion in (NH4)2SO4 solutions with various concentrations. (b) Tensile stress–strain curves of the gelatin/PAM and gelatin/PAM-A hydrogels. (c) Frequency sweep data of the gelatin/PAM and gelatin/PAM-A hydrogels in terms of (filled symbols) G′ and (open symbols) G′′.
