Well-defined stimuli-responsive alkali-soluble poly(methacrylic acid)-block-[60]fullerene (PMAA-b-C-60) was synthesized via atom transfer radical polymerization (ATRP): and its aggregation behavior in aqueous solution was examined using potentiometric and conductometric titrations. Static and dynamic light scattering, and transmission electron microscopic (TEM) techniques. PMA-b-C-60 shows pH-responsive and water-soluble properties at high pH. In dilute solution. the micelles and large secondary aggregates, which are independent of polymer concentration. coexist in solution. The R-h of micelles-increases from 6 to 10 nm with increasing degree of neutralization and remains constant at 10 nm with the addition of salt. However, the R-h of large aggregates increases from 91 to 153 nm with increasing degree of neutralization and decreases from 153 to 105 nm with increasing NaCl concentration. TEM studies revealed that the large aggregates comprise of individual micelles and possess microstructure similar to large compound micelles (LCM).