We report QENS measurements from PS-b-PFOA aggregates in supercritical CO2. Line shapes are dominated by localized diffusive modes and segmental dynamics of the anchored, finite-length PFOA chains. For Q less than or equal to 0.6 Angstrom(-1), we obtain effective diffusion coefficients of congruent to 0.8 10(-6) cm(2)/s. At higher Q, a single component is not sufficient as shown by excess intensity on the flanks. For Q greater than or equal to 1.5 Angstrom(-1), the wings reflect contributions due to a distribution of faster, more localized chain modes. (C) 2000 Elsevier Science B.V. AII rights reserved.