To understand the role the soft and hard networks play and their synergistically mechanical enhancement mechanism, single network hydrogels SPAAc (soft) and HPAAc-[Fe.sup.3+] (hard) were prepared and their performance was compared with that of the dual crosslinked SHPAAc-[Fe.sup.3+] (Fig.
(a) Stress and strain profiles, (b) Loading-unloading test under 800% strain, (c) Elastic modulus and toughness, (d) Tearing energy and dissipated energy of SPAAc, HPAAc-[Fe.sup.3+], and SHPAAc-[Fe.sup.3+] hydrogels.