The ionization of the microgel releases counterions, which lead to swelling in turn. Figure shows the microgel swelling ratio a eq /a 0 as function of pH res . As expected, for low and intermediate pH res values, the swelling is controlled by the ionization of the weak acid sites in the polymer network. We observe that all systems swell with an increase in pH res , saturating around the pH res values where the maximum ionization is reached. Beyond this point, further increasing pH res does not affect the ionization degree, but modifies the screening, reflected in an increase of the reservoir screening length κ res 7 and a concomitant deswelling.