(649g) Disentangling the Effects of Polymer Matrix Chain Length and Processing Conditions on Nanorod Assembly in Polymer Nanocomposites

Polymer nanocomposites (PNCs) refer to a class of soft materials which comprise a polymer matrix with nanoparticle fillers. The inclusion of nanofillers, specifically anisotropic particles such as nanorods, results in soft materials with enhanced mechanical, thermal, and optical properties versus neat, polymer melts. Therefore, a fundamental understanding of the structure-property relationships and nonequilibrium phase behavior of PNCs is essential to enable the fabrication of multifunctional soft materials. In this talk, we describe equilibrium and nonequilibrium coarse-grained molecular dynamics simulations of thin nanorods in polymer melts and show that nanorod assembly depends on the matrix chain length as well as the nanorod length and concentration. Simulations show that nanorods undergo shear-driven alignment and aggregate to form bundles via attractive, bridging interactions between nanorods and matrix chains. Increasing nanorod length promotes nanorod assembly at equivalent shear rates but has a negligible effect at equivalent Peclet numbers. Finally, simulations show that matrix chain length shifts the isotropic-to-nematic transition volume fraction. Overall, our results highlight how subtle differences in nanorod design, matrix chain length, and processing conditions can significantly alter PNC assembly and structure, thus creating new design opportunities for engineered nanocomposites.