The systematic deviations of the theoretical models at low and large ζ can be then attributed to the strong counterionpolymer correlations induced by the chain-like structure of the network, with minor influence of the disregard for polymer and ion excluded volumes as well as ion correlations in the mean-field approach. The presence of excluded-volume effects in simulations lead into a stronger swelling due to larger end-to-end distances of the polymer chains because of the excluded volume of the monomers and a reduction in the screening inside the microgel because of ion correlations. This results in the steeper swelling at low ζ . In the theoretical model, the differences with the simulations can be bypassed by fine tuning φ coll for low and high ζ , in particular with Langevin model.