The SPC/E water model is used as an explicit solvent . Unless otherwise noted, the hydrogel network is solvated by approximately 8000 water molecules to obtain an AA density of ρ ≈ 1.14 g/mL for our highly swollen PAA hydrogel models at a temperature of T = 300 K and under an isotropic pressure of P = 1 atm. These water contents correspond to a solvent volume fraction of around >90% in the cubic simulation box with dimensions of L 0 ≈ 6.2 nm. The bonded interaction are taken care of via the OPLS-AA force-field, which is a commonly employed force field to study polymeric systems at the atomic resolution, including PAA chains . All bonded and non-bonded interactions are calculated by using the tabulated pair-wise interaction coefficients . Specifically, the short-range Coulomb interactions between two atoms with charges q i and q j separated by a distance r ij are calculated via