Using capillary viscometry, we have investigated the associative behavior of new amphiphilic telechelics incorporating polyhedral oligo-silsesquioxane, (POSS) as an end-group of poly(ethylene glycol) (PEG) chains of varying length. Solution viscosities were strongly affected by the solvent composition in THF/water mixtures. When water, a selective solvent for PEO segments but a selective non-solvent for POSS segments, was added to the THF solutions, behavior common to polyelectrolytes was observed. In particular, for relatively high concentrations the reduced viscosity remained nearly concentration-invariant for both POSS telechelics and pure PEG homopolymers, indicating a limiting molecular weight of aggregates. On the other hand, a dramatic increase in the reduced viscosity was observed with decreasing concentration for lower concentration values, suggesting aggregate formation and a concentration-dependent aggregate size. (c) 2006 Elsevier Ltd. All rights reserved.