Elasticity of nanoparticle chain aggregates: implications for polymer fillers and surface coatings

Nanoparticle chain aggregates (NCA) of inorganic oxides have elastic properties. The NCA of titania, alumina and iron oxide generated by laser ablation were deposited on an electron microscope grid. Expanding holes in the films on the grid produced by the electron beam caused the chains to stretch up to about twice their original length before snapping back. The NCA were several tenths of a micron long and were composed of 5–10 nm primary particles. Mechanisms for NCA elasticity are proposed. The application of these concepts to improving the properties of composites of NCA and molecular polymers (e.g., rubber) and to NCA coatings with special optical properties is discussed. The need to develop methods for the synthesis of NCA with prescribed primary particle size, chain length and other properties follows from these applications.