(667c) Structure and Deformation Response of Rod-Containing Nanocomposites

Toepperwein, G. N. - Presenter, University of Wisconsin, Madison

Addition of nanoparticles, such as metallic nanoparticles or carbon nanotubes, into a polymer drastically affects the mechanical properties of the resultant nanocomposite. This includes elastic modulus, a function of localrdering, and hardening modulus, a function of chain topology. Adequate experimental analysis is frustrated by challenges associated with sample preparation and particle dispersion, prompting this work's use of Monte Carlo of molecular dynamics simulation of course-grained models to provide a accurate nano-scale view of these nanocomposite systems. Studies into the nature of these changes have examined a large parameter space of variables including particle size, effective surface interactions, concentration, and thermal history. However, comparatively few works have examined the role of nanoparticle geometry. To that end 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. This work first examines the organization of nanorods at different concentrations and comments on resulting alignment behavior of polymer as it changes with particle size. Second, deformation of nanocomposites reveals changes in the elastic behavior, strain-softening behavior, and hardening modulus as a function of rod length. Third, recently developed algorithms that allow for the extraction of primitive path from simulation configurations are used to describe how particles affect the underlying polymer entanglement network, as well as how that network evolves due to particle diffusion. Fourth, this work studies how bridged polymer-particle network topology depends on nanorod length and orientation, including during deformation. 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.