Spinodal clustering in thin films of nanoparticle-polymer mixtures

Thin supported polystyrene-C(60) fullerene mixtures annealed above their glass transition temperature develop spinodal surface undulations which depend on film thickness h(20-500  nm), polymer molecular mass M(w), temperature, and time t. The dominant wavelength λ ∼1-10  μm scales linearly with h and coarsening kinetics follow λ∼t{α}, with 0< α(h) < 1/3; the morphology eventually pins at long times. This spinodal surface excitation contrasts with dewetting suppression and film stability observed in low -M(w) polymers and results from the interplay of binary miscibility and fullerene substrate attraction.