Mobile nanoparticles and their effect on phase separation dynamics in thin-film polymer blends

We present a systematic study of mobile nanoparticles (NP) and their effect on phase separation dynamics in polymer blend films. Starting with a homogeneous dispersion of silica NP in PMMA:SAN films, the NP are observed to partition into the PMMA-rich phase and stratify during phase separation. The correlation length. between phases grows as xisimilar tot(1/3) for blends containing 0, 2, and 5 wt% NP. However, phase size decreases as the wt% of NP increases. This behavior agrees with a coalescence model, which incorporates an increase in viscosity due to the NP.