A C-60 derivatized triarm poly(ethylene oxide) copolymer was synthesized and characterized. The soluble polymer produced spread at aqueous interfaces to form highly expanded fluid Langmuir monolayers. The onset area of 1300 Angstrom(2)/arm is likely due to the polymer disrupting cohesion between C-60 units. Compression/expansion studies revealed a significant elastic region, beyond which the C-60 units condensed, and a compact rigid and irreversible monolayer formed.