To sample various conformations and ionization states of the microgel, we perform hybrid MD/MC simulations. The spatial conformations at a fixed particle number are explored using Langevin dynamics, allowing us to sample the system at a fixed temperature. For this purpose, we numerically integrate the Langevin equation using the Velocity-Verlet integrator with a time step of ∆t = 0.01 in Lennard-Jones units. In the simulations, we use the P 3 M method to efficiently sum up the electrostatic interactions. Further details of the simulations regarding the microgel model and the time evolution can be found in the Ref. by the same authors. The chemical equilibria of the monomers, which can be either acidic or basic, as well as the coupling to a reservoir at a fixed chemical composition (pH-value and salt concentration) are taken into account using the grand-reaction method. We note again that the reservoir is a purely theoretical construct that has no direct analogue in typical microgel swelling experiments. In principle, using a different simulation approach, 49 one could also directly access the pH within the system. However, since a reservoir is employed both in the theory and the simulations, this step is not necessary when performing a direct comparison between them. In short, the grand-reaction method consists of Monte Carlo moves that correspond to the various chemical reactions, i.e. Eqs. 5 and 11, as well as particle exchanges of the reservoir, which can formally be represented as "virtual" chemical reactions: