Nanocomposites: Anarchy, Democracy or Hierarchy?
Dale W. Schaefer
Department of Chemical and Materials Engineering
University of Cincinnati
Cincinnati, OH 45208
Nanocomposites: Anarchy, Democracy or Hierarchy?By definition, nanocomposites display morphological features on the nanometer scale. Nanoscale particles, domains, tubes, sheets are evident by electron imaging techniques. What is less widely appreciated is that morphological features usually extend to much larger length scales. Often hierarchical relationships among various levels of structure occur such as particles aggregated into clusters that in turn form micron-sized agglomerates. Hierarchical morphologies that are often missed in imaging are evident in scattering experiments. Imaging and scattering data will be compared and contrasted for several classes of polymer-based nanocomposites: silica-filled elastomers, in situ filled silicones, carbon nanotubes and clays dispersed in solvents and polymers, polymer-dispersed liquid crystals. Based on a combination of x-ray and light scattering, it is evident that all these systems are much more complex than is generally appreciated. The reasons these features are often missed in imaging work will be discussed.