Diffusion of Thin Nanorods in Polymer Melts.

The diffusion of monomerically thin nanorods in polymer melts is studied by molecular dynamics simulations. We focus on the systems where chains are long enough to screen the hydrodynamic interactions such that the diffusion coefficient D_∥ for the direction parallel to the rod decreases linearly with increasing rod length l. In unentangled polymers, the diffusion coefficient for the direction normal to the rod exhibits a crossover from D_⊥ ~ l^-2 to D_⊥ ~ l^-1 with increasing l, corresponding to a progressive coupling of nanorod motion to the polymers. Accordingly, the rotational diffusion coefficient D_R ≈ D_⊥l^-2 ~ l^-4 and then D_R ~ l^-3 as l increases. In entangled polymers, D_⊥ and D_R are suppressed for l larger than the entanglement mesh size a. D_⊥ ~ l^-3 and D_R ~ l^-5 for l sufficiently above a in agreement with de Gennes' rod reptation model.

Duke Scholars

Author Michael Rubinstein Thomas Lord Department of Mechanical Engineering and Materia ...