Micellization of the stoichiometric complex of polystyrene-b-poly(4-vinylpyridine) with formic acid [(PS-b-P4VP)/FA] takes place in chloroform. When the concentration of the block copolymer is less than or equal to 5.0 mg/mL, the micellization leads to regular spherical micelles; while when the concentration of the copolymer is higher than or equal to 10.0 mg/mL, precipitates are produced. A stoichiometric complex of PS-b-P4VP/decanoic acid (DA) can be molecularly dispersed in chloroform, but introducing a stoichiometric amount of FA into the solution of PS-b-P4VP/DA leads also to the formation of regular spherical micelles. In this system, the pyridine/DA can be replaced by the pyridine/FA units, and the latter will associate. There is a balance between these two kinds of complexed units in the final mixture. It is thought that the preference of the pyridine units for DA will retard the complexation of the copolymer with FA and the resultant micellization; the remaining pyridine/DA complexed units will also retard the association among pyridine/FA units and change the balance between the aggregation effect of the complexed P4VP block and the solubilization effect of the PS block. As a result, the micellization can be conducted at the concentrations of PS-b-P4VP up to 50.0 mg/mL, resulting in regular micelles, and the micellization at the concentration of the copolymer lower than or equal to 10.0 mg/mL exhibits the thermodynamically controlled micellization.