Figure 1.

Illustration of the internal crosslinked networks of the as-prepared CMCS-Ca²⁺/PAAm/PNMA hydrogels of (a) strong hydrogen bond crosslinking from poly(N-methylol acrylamide) (PNMA) and (b) weak hydrogen bond and metal coordination interaction between carboxymethyl chitosan (CMCS) and Ca²⁺; (c) ultraviolet–visible (UV–vis) transmittance spectra of the as-prepared CMCS-Ca²⁺/PAAm/PNMA hydrogels; (d) Fourier transform infrared spectoscopy (FT-IR) spectra of CMCS, PAAm/PNMA and CMCS-Ca²⁺/PAAm/PNMA hydrogels.