Polymer nanocomposites are organic inorganic hybrid materials where the inorganic filler has at least one dimension in the nanometer scale. During the past two decades, research into nanocomposites has led to the development of materials with properties that are far superior to those of not only the parent materials but also of conventional microcomposites. The superiority of polymer nanocomposites compared to their micro-counterparts is often attributed to the availability of large numbers of nanoparticles with huge interfacial areas and the confinement of polymer matrix chains at the nano-level. Despite their huge potential, there are a number of critical issues associated with these materials, including their processing, dispersion/distribution of nanoparticles in a matrix, surface modification and compatibility among the different phases, and controlled micro- to nano-structures. These problems need to be addressed before the full potential of polymer nanocomposites can be realized. On the positive note, this growing combination of complex problems has resulted in significant research and developmental activities on these materials. This book covers a range of functional and physical properties of polymer nanocomposites, combining basic theory as well as advanced and in-depth knowledge on these properties. Also included is one chapter on characterization of nanocomposites.