Au metal nanoparticles embedded in polymer matrices aggregate at elevated temperatures overcoming the barrier induced by entanglement of polymer chains. The temperature required for nanoparticle agglomeration depends on the polymer chain length, providing a measure of the potential barrier induced by entanglement of polymer chains. For higher chain lengths a non-linear dependence of the aggregation temperature with molecular weight was found. These results suggest that, in addition to the role of nanoparticle-polymer interactions, polymer-polymer interactions influence the aggregation of the nanoparticles. (C) 2012 Elsevier B.V. All rights reserved.