Simultaneous coordination‐association and electrostatic‐repulsion interactions play critical roles in the construction and stabilization of enzymatic function metal centers in water media. These interactions are promising for construction and self‐assembly of artificial aqueous polymer single‐chain nanoparticles (SCNPs). Herein, the construction and self‐assembly of dative‐bonded aqueous SCNPs are reported via simultaneous coordination‐association and electrostatic‐repulsion interactions within single chains of histamine‐based hydrophilic block copolymer. The electrostatic‐repulsion interactions are tunable through adjusting the imidazolium/imidazole ratio in response to pH, and in situ Cu(II)‐coordination leads to the intramolecular association and single‐chain collapse in acidic water. SCNPs are stabilized by the electrostatic repulsion of dative‐bonded block and steric shielding of nonionic water‐soluble block, and have a huge specific surface area of function metal centers accessible to substrates in acidic water. Moreover, SCNPs can assemble into micelles, networks, and large particles programmably in response to the solution pH. These unique media‐sensitive phase‐transformation behaviors provide a general, facile, and versatile platform for the fabrication of enzyme‐inspired smart aqueous catalysts.
