AbstractPhase segregation between different macromolecules and specific weak interactions are the basis of molecular organization in many biological systems, which are held together by attractive hydrogen bonds (H‐bonds) and dissociated by phase segregation. We report significant changes in the association behavior of covalent H‐bonds by the phase of attached polymer chains. Depending on the aggregation state, we observed either intact H‐bonds despite segregation of the phases, or macrophase separation with a larger amount of H‐bonding dissociation.