Using Polymer Thin Films to Model Nanocomposites

Polymer thin films spin-coated on certain substrates, such as oxide silicon wafer and HOPG, can be used as a one-dimensional model to investigate the interactions near the polymer-nanoparticle (e.g. montmorillonite (MMT) and carbon nanotubes) interface in nanocomposites. In this study, we used differential scanning calorimetry (DSC), AFM nanoindentation, gold nanoparticle embedding technology, positron annihilation lifetime (PAL) spectroscopy and ellipsometry to measure the average and local properties such as glass transition temperature (Tg), free volume and elastic modulus for polymer thin films with different thicknesses. Surface of silicon wafer and HOPG is acid treated and grafted with surfactants and block copolymers prepared by atom transfer radical polymerization (ATRP) as in nanocomposite synthesis. The difference in the interactions between polymer and modified substrate or unmodified substrate compared well with that observed in nanocomposites.