(181ax) Effect of Thermal History on Particle Structure and Dynamics in Polymer Nanocomposites

Research around polymer nanocomposites largely focuses on controlling the nanofiller structure with the aim of improving specific properties - a direct result of the dynamic polymer-particle interactions. The structure of these samples is tuned with three classes of composites - (1) bare nanoparticles in a polymer matrix, (2) nanoparticles with densely tethered brushes dispersed in a polymer matrix, and (3) systems composed solely of nanoparticles grafted with densely tethered long polymer chains. Past work on these materials has been shown to have improved mechanical properties, anisotropic morphologies, polymer crystallization based reinforcement, and enhanced gas transport properties in different combinations of materials. The process for making these materials typically involves a high-temperature annealing step, above the glass transition of the polymer, in order to equilibrate the sample and remove any thermal history. This work addresses the general concept of thermally annealing these nanoparticle filled polymer systems. Specifically, we demonstrate to what extent the nanoparticle structure and dynamics equilibrate at temperatures greater than the glass transition, and how the chosen annealing temperature can have significant effects on the resulting macroscopic properties.