H-1, Li-7, and Na-23 NMR spectra and relaxations were measured with Li and Na salts of poly(acrylic acid) (PAAcLi : PAAcNa) and of poly(methyl methacrylate)-block-poly(acrylic acid) (PMMA-PAAcLi. PMMA-PAAcNa) micelles at 300 Kin D2O at concentrations from 0.5 to 0.005% w/w. The results show a close similarity in the dependences of polyacrylic chain mobility in PAAcM and PMMA-PAAcM (M = Pda, Li)on concentration and indicate that chain stiffness increases with dilution. The analogy of behavior between free linear polyacrylic chains and those bound to a rigid micellar core, which cannot be locally diluted, indicates that the collective interchain and intermicellar interactions have an important effect on the local state on the level of individual monomeric units.