posted on 2024-02-27, 21:04authored byPhillip A. Taylor, Jiuling Wang, Ting Ge, Thomas C. O’Connor, Gary S. Grest
Coarse-grained molecular dynamics simulations are used
to study
the diffusion of thin nanorods in entangled polymer melts for varying
nanorod length and roughness. While prior studies observed a nanorod
parallel diffusion constant scaling inversely with rod length D∥ ∼ l–1, here, we show that this scaling is not universal and depends sensitively
on the nanorod surface roughness. We observe D∥ ∼ l–k, where k < 1 and decreases with decreasing
surface roughness. The weaker scaling is driven by the non-Gaussian
diffusion of nanorods due to the emergence of an intermittent hopping
process that becomes more pronounced with decreasing roughness at
the monomer scale. Analysis shows that the mean hop size grows for
smoother rods but shows little to no variation with rod length. The
mean hopping frequency shows no dependence on either rod length or
roughness, suggesting it originates from the polymer melt environment.
Our results show that the small-scale features of the nanorod surface
strongly influence the large-scale and long-time transport of nanorods
in polymer matrices, creating new material design opportunities for
precisely engineered nanocomposites.