Impacts of nanofiller shapes on the interface confinement effect in polymer nanocomposites

Shape effect of nanofillers (NFs) on the properties of nanocomposites has attracted considerable attention in recent research. The present study aims to examine how NF shapes influence the confinement effect of polymer -NF interface on the physical properties of nearby polymer (the interphase). Herein molecular dynamics simulations are performed to capture the shift of interphase properties when NFs change from nanosphere to nanocylinder and nanofilm geometry. A stress analysis is then carried out in the interphase to identify a key parameter for characterizing the stress-property coupling and revealing the pathway of the NF shapes to impact the interphase properties. It is shown that the peak hydrostatic stress sigma hyd quantifies the effect of internal stresses on the properties of the interphase. Specifically, the shape transition considered can substantially enhance the peak sigma hyd by flattening the stress space in the interphase without largely affecting the polymer-NF interaction. Increased peak sigma hyd in turn upshifts the interphase properties and thus, leads to the coupling between the NF shapes and interface confinement effect.