Structure-property insights of ZnO-embedded poly(acrylamide-co-itaconic acid) hybrid networks functionalized with carboxymethyl cellulose, collagen, L-arginine, or dextrin.

Integration of various organic components systematically modulates the macroscopic properties of zinc oxide@poly(acrylamide-co-itaconic acid)-mace (ZnO@PAIM) anionic gels. The effects of structurally diverse auxiliary components; carboxymethyl cellulose (CMC), collagen (COL), L-arginine (ARG), and dextrin (DEX) were investigated in terms of equilibrium swelling, polymer-solvent interaction parameter χ, and compressive modulus in the as-prepared G₀ and swollen G states. Due to cryoconcentration effect, freeze-polymerized cryogels formed at -18 °C exhibited restricted swelling and 2- to 4-fold mechanical enhancement, reaching 1419.2 ± 162.9 Pa for ARG-integrated hybrid cryogels. Swelling ratios followed Blank > ARG > DEX > CMC > COL, consistent with increasing χ values toward theta threshold (χ ≈ 0.5). COL-integrated hybrids showed lowest swelling and highest χ value (0.4656 ± 0.0012), accompanied by a moderate effective cross-linking density (νe = 6.146 ± 0.917 mol/m3). Reflecting short-chain plasticization, ZnO@PAIM-DEX hybrids exhibited lowest cross-linking efficiency and highest network chain length (N = 22,456.1 ± 4651.7). CMC-integrated hydrogels retained highest as-prepared stiffness despite swelling-induced network relaxation (G < G₀), with a restricted molecular weight between cross-links (Mc = 142.90 ± 23.73 kg/mol). Regarding responsive swelling behavior, increasing NaCl concentration from 10-5 to 1.0 M caused 9.1-, 5.7-, and 4.3-fold volume reductions in Blank, CMC-, and COL-integrated hybrids, respectively. Alternating pH between 2.1 and 11.2 produced highly reversible swelling/deswelling transitions associated with protonation/deprotonation of itaconic acid groups. These dynamic features highlight the reversible stimuli-responsive adaptability of anionic ZnO@PAIM gels, demonstrating their potential for advanced flexible hybrid platforms with tunable elasticity for emerging smart material applications.