The phase of of the supernatant, denoted by the superscript sup , contains only small ions and other solutes in implicit solvent but it does not contain any polymer. Unlike the polyelectrolyte complex phase, we set the Bjerrum length in the supernatant to l sup B = 0.71 nm, which corresponds to the permittivity of pure water at room temperature, ε r ≈ 78. Otherwise, all other interactions in the supernatant phase are the same as in the polyelectrolyte complex phase.