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The paper describes the pH-dependent self-assembly of a diblock copolymer, poly(2-vinylpyridine)-block-poly(ethylene oxide), P2VP–PEO in aqueous media using computer simulations. We employed the dissipative particle dynamics (DPD) method and found that the copolymer with electrically neutral (i.e., deprotonated) or very low-protonated P2VP blocks form multimolecular spherical core–shell micelles with insoluble P2VP cores in neutral and alkaline solutions, while protonization (ionization) of P2VP blocks exceeding 25% provokes the dissociation of micelles in single chains in acidic media. The finding that a clearly pronounced transition occurs in a restricted pH region slightly above pK_A^ap (where pK_A^ap is the apparent dissociation constant of the conjugated acid P2VPH⁺) is in good agreement with the experimental data (Macromolecules 1996, 29, 6071−6073). This suggests that (i) the tested model is …