Conformational behaviors of a charged-neutral star micelle in salt-free solution.

The conformational behaviors of charged brushes on a micelle self-assembled by charged-neutral diblock copolymers in salt-free solution are extensively analyzed using a coarse-grained dissipative particle dynamic (DPD) simulation. When only monovalent counterions exist, the brush conformation of the corona in the micelle is exactly consistent with the predictions from the blob-scaling theory based on the spherical polyelectrolyte brush model, which differentiates the system into three distinct regimes: (I) quasi-neutral regime, (II) "Pincus" regime, and (III) osmotic regime. For multivalent counterions such as divalence and trivalence, however, the strong electrostatic correlations lead the micelle structures to deviate obviously from those of scaling predictions. The collapse of the brush appears to be due to the drop in the osmotic pressure inside the corona region of the micelle.