Conference Dates

November 8-12, 2015


Matrix free assemblies of polymer-grafted, “hairy” nanoparticles (HNP) exhibit novel morphology, dielectric and mechanical properties, as well as providing means to overcome dispersion challenges ubiquitous to conventional polymer-inorganic blended nanocomposites. Physical aging of the amorphous polymer glass between the close-packed nanoparticles (NPs) will dominate long-term stability. However, the energetics of cooperative relaxation of tethered chains confined within the interstitial spaces in single component nanocomposites is unknown. Herein, we compare glass transition temperature (Tg) and physical aging behavior of matrix free assemblies of HNPs (aHNPs) to conventional NP-polymer blends, across different nano-silica loadings (0-50 v/v%) and brush architecture of grafted polystyrene chains in aHNPs. At low to intermediate silica volume fraction, the Tg of blended nanocomposites is independent of silica content, whereas for aHNPs the Tg decreases with silica content, implying that chain tethering decreases local segment density near the NP interface irrespective of chain composition, molecular weight or polymer-NP interactions. In contrast, the Tg of the aHNPs is higher than linear polystyrene of comparable molecular weight to the graft, implying that cooperativity is constrained. Within the glass (T