Monday  |  Salon 11  |  02:10 PM–02:30 PM

#15990, AFM Nanomechanical Measurements of Controlled Interphase Patterns for Nanocomposite Design

Polymer nanocomposites have been shown to exhibit a variety of enhanced properties such as modulus and toughness. The origin of these enhancements has been assigned in part to a region of polymer material near the nanofiller interfaces with altered properties, known as interphase. Our group has previously measured the apparent elastic modulus of the interphase region with Atomic Force Microscopy Nanomechanical Mapping (AFM-NM) by constructing thin films of polymer sandwiched between glass slides and cross-sectioning with fracture or argon ion mill. These measurements agreed with complementary fluorescence measurements of glass transition temperature and show a synergistic enhancement when interfaces are close to each other (~ 50 nm).

Our new experiments explicitly explore additional degrees of freedom in the polymer confinement near the hard support material by patterning silicon wafers with physical and chemical patterns using lithographic techniques. This patterning approach allows curvature and interaction to vary on a micron scale which, when combined with appropriate cross-sectioning and AFM-NM measurements, allows several processing conditions and therefore interphase states to be measured simultaneously with the same probe at the same time, supporting meaningful comparisons of interphase properties. This talk explores our results in the context of empirical substrate effect subtraction techniques as well as explicit finite element modeling of scale-free indentations to parse out material property gradients in the interphase from other confounding stress interaction phenomena.

Richard Sheridan   Duke University
Heer Majithia   Duke University
Stefan Zauscher   Duke University
Cate Brinson   Duke University