Polymer Nanocomposite Interfaces: The Hidden Lever for Optimizing Performance in Spherical Nanofilled Polymers

Polymer nanocomposites consist of at least two phases: a polymeric matrix phase and an inorganic nanofiller phase. To enhance the overall performance of polymer nanocomposites, efforts have been made to improve the intrinsic properties of both the matrix and the nanofiller. A hidden lever for performance optimization, however, lies in understanding and tailoring the matrix/filler interface. Depending on the dispersion state of the nanofiller and the interface area, the resulting interfacial region can be a critical component in polymer nanocomposites. Generally, uniform nanofiller dispersion, which maximizes interface area and therefore the volume of the interfacial region, is desirable. This chapter will first briefly discuss the thermodynamic mechanisms governing nanofiller dispersion. The thermodynamic matrix/filler interactions also influence the structure and properties of the interfacial region, which can be significantly different from the bulk material. Examples of such structural modification in semicystalline and thermoset polymer nanocomposites will be given. Deviations in polymer properties, such as the change in molecular mobility in the interfacial region, influence the macroscopic mechanical and dielectric properties of the polymer nanocomposite. However, measuring these properties is a challenge because of the hidden nature of the interfacial region. The measurement techniques can be broadly divided into direct and indirect methods. The direct methods rely on the use of probes to directly measure the local properties at the interface while indirect methods deduce the interface properties by analyzing differences in the measurements from bulk composites and the neat matrix.