In recent years the blending of 0-, 1-, and 2- dimensional inorganic fillers such as POSS, carbon nanotubes, and nano-clay platelets into polymeric matrices enabled exploration of various filler/matrix combinations on mechanical properties. However, a fundamental understanding of the connections amongst the microstructure and macroscopic properties of polymeric based nanocomposites are yet to be fully explored to optimize the truly multifunctional property potential of polymer nanocomposites. Polyhedral oligomeric silsesquioxane (POSS) offers a unique approach to examine the effect of molecularly dispersed nanoscopic fillers on rheological properties of entangled polymer melts. Experiments were performed using a nearly-monodisperse molecular weight polystyrene (PS) blended with varying amounts of two fully condensed POSS molecules surrounded with phenethyl and styrenyl groups. Due to the chemical similarity between these organic moieties surrounding the silicon-oxygen framework (SiO1.5) of POSS and PS, we were able to obtain polymer blends with molecular dispersed nanoscopic fillers needed to study the effect of intermolecular nanoparticle-nanoparticle interactions and the associated intramolecular interactions on the dynamics of the polymer chains. Differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM) were used to characterize the thermal properties and morphologies of the POSS/PS blends. Oscillatory shear both small and large and/or tensile method was used to probe the dynamics of polymer chains as influenced by the addition of different chemical moiety of POSS at the glass transition, rubbery state and the terminal-flow transition regions. Further studies were done with varying molecular weight of PS for understanding of the chain length effects on the phase behavior of the blends, results obtained from the thermal and mechanical characterization methods were compared with morphological observations to better understand the structure-property relationship of polymers containing molecularly dispersed nanoscopic fillers.
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