Preparation and Characterization of Thermodynamically Controlled Polymer Nanocomposites

The mechanical and physical properties of polymeric materials can be greatly improved by adding nanoscale additives. To mediate the dispersion of nanoparticles in polymers, it is often necessary to modify their surfaces to prevent aggregation. While polymer nanocomposites system consisting of homopolymer-grafted nanoparticles are well understood, copolymer-functionalized nanoparticles are less well understood but provide additional ways to alter dispersion through the use of chemically different comonomers. In this thesis, polystyrene nanocomposites blended with copolymer-grafted nanoparticles were prepared and studied. The particular comonomers used were methyl methacrylate and cyclohexyl methacrylate, which provides miscibility with polystyrene. Polymers with varying comonomer ratios were synthesized via atom transfer radical polymerization and grafted onto silica nanoparticle surfaces. The functionalized particles were then dispersed into polystyrene to make polymer nanocomposites. The resulting materials were characterized by differential scanning calorimeter and atomic force microscopy and the role of the grafted polymer composition on the glass transition temperature of the nanocomposites and the dispersion state of the nanoparticles was examined. These results provide preliminary insight into how random copolymers can affect polymer nanocomposite structure and properties.