(711e) Deformation Response and Void Formation in Rod-Containing Nanocomposites

The mechanical strength and response of polymeric materials is drastically altered by the inclusion of nanoparticles, ranging from metallic crystals to carbon nanotubes. These effects are present both in the elastic regime, which is dominated by local ordering, as well as post-yield regime, where chain topology is key. A better understanding of the dependence of reinforcement upon additive properties could potentially lead to design of optimal additives for specific applications. Considerable work has been done in past to elucidate the role of several properties including concentration, particle size, effective surface interactions, and thermal history. However, comparatively few works have examined the role of nanoparticle geometry. Challenges associated with sample preparation and particle dispersion frustrate adequate experimental analysis. In this work, a combination of Monte Carlo and molecular dynamics simulation is used to equilibrate and examine these difficult systems. We have examined the effect of introducing various length nanorods into polymeric materials via course-grained simulation, and applied the plethora of well-developed techniques that have previously been used to study spherical-particle nanocomposite systems in order to develop an accurate nano-scale view of these nanocomposite systems. This work first examines the distribution of nanorods into the polymer matrix. Second, deformation of nanocomposites reveals changes in the elastic behavior, strain-softening behavior, and hardening modulus as a function of rod length. Third, the onset of crazing is examined and its origins in local void formation probed. Fourth, measurement of local mechanical properties reveals the connection between local order, nanoparticle location, and site failure. The primary result of these efforts is a characterization of how anisotropic rods fundamentally alter polymer behavior on the nanoscale resulting in magnified macroscopic observables.