We report the polymer conformation and fullerene
aggregation in a ternary system containing polystyrene, C60, and
toluene measured by small angle neutron, static, and dynamic light
scattering. We investigate polymer concentrations across the dilute
and semidilute regime for five polymer molecular weights (Mw =
20 kg/mol to 1 Mg/mol), and fullerene concentrations below and
above its miscibility threshold in toluene. We find that the polymer
radius of gyration (Rg
poly), hydrodynamic radius (Rh), and the
mixture correlation length (ξ) remain unchanged upon addition of
C60. The miscibility of C60 in toluene, however, decreases upon addition of polystyrene forming aggregates with a timedependent
radius on the order of 100 nm, and this effect is amplified with increasing polymer Mw. Our findings are relevant to
the solution processing of organic photovoltaics, which generally require the effective solubilization of fullerene derivatives and
polymer pairs in this concentration range.