Effect of the Nature of Metal Ions and the Type of Solvent on the Mechanical, Self-Healing and Conductive Properties of Poly(AA-Co-AAm) Gels.

Composite hydrogel based on acrylic acid and acrylamide, modified with metal ions (Ni2+, Al3+, Fe2+, Fe3+) with concentration 0.3 wt%, were synthesized in water or polyethylene glycol (with a molecular weight of 400 Da) at three monomer ratios (7/3, 1/1, 3/7). Dynamic mechanical analysis shows that the equilibrium modulus of elasticity (Ge) of unmodified hydrogels increases with acrylamide content due to higher crosslinking density (ne) and smaller cell size. AlCl3 or NiCl2 strengthen the structure (Ge increases +53.5% in a 1/1 ratio), while iron salts cause softening (decreases to 90% when using FeC2O4). Partial replacement of polyethylene glycol reduces the elasticity but when using AlCl3 happens synergistic increase ne 1.9 times in the ratio 3/7. The self-healing efficiency reaches ~100% for FeCl3 in PEG gel in a ratio of 1/1 and 72.1% for Fe(NH4)2(SO4)2 hydrogel in 3/7. The electrical conductivity of hydrogels increases in the range of Al3+>Ni2+>Fe3+, while matrix based on polyethylene glycol reduces the conductivity by an order of magnitude. For Ni2+-containing samples, pinched hysteresis loops are observed in both water and polyethylene glycol. In contrast, Al3+ causes rapid passivation in the water matrix, while in the matrix based on polyethylene glycol, the current-voltage characteristics follow ohmic behavior. The results demonstrate the possibility of directional regulation of the mechanical, electrical, and self-healing efficiency of hydrogels by selecting the ratio of monomers, the nature of the ion modifier, and the type of solvent.