Segmental dynamics and physical aging of polystyrene/silver nanocomposites

Abstract

We investigate the effects of silver (Ag) nanoparticles on the segmental and chain dynamics, physical aging and rheological behavior of polystyrene (PS) via a combination of broadband dielectric spectroscopy, calorimetry, and dynamic rheological measurement. The segmental dynamics of PS is found to be unchanged with increasing nanoparticle loading. After annealing below the glass transition temperature (T_g) for various time periods and measuring the recovered enthalpy values of PS, it is surprising that an acceleration and a suppression of the physical aging in PS/Ag-3% and 10% nanocomposites can be observed, respectively, corresponding to the decreased and increased calorimetric T_g, which can be interpreted by plasticizing and antiplasticizing effects. Furthermore, the filler reinforcement in rheological behavior is observed with increased weight fraction of Ag nanoparticles. The temperature-dependent horizontal shift factor reveals that the overall chain dynamics speed up in the presence of Ag nanoparticles. We also emphasize recent discrepancies in the prior studies of polymer nanocomposites and polymer thin films by comparing results.