  Molecular dynamics simulations were conducted to investigate the dynamic
properties of melts of nonconcatenated ring polymers and compared to melts of
linear polymers. The longest rings were composed of N=1600 monomers per chain
which corresponds to roughly 57 entanglement lengths for comparable linear
polymers. The ring melts were found to diffuse faster than their linear
counterparts, with the self-diffusion coefficient for both architectures
scaling as approximately N to the -2.4 power for large N. The mean-square
displacement of the center-of-mass of the rings follows a sub-diffusive
behavior for times and distances beyond the mean-square gyration radius,
neither compatible with the Rouse nor the reptation model. The rings relax
stress much faster than linear polymers and the zero-shear viscosity was found
to vary as approximately N to the 1.4 power which is much weaker than the N to
the 3.4 power of linear chains, not matching any commonly known model for
polymer dynamics when compared to the observed mean-square displacements. These
findings are discussed in view of the conformational properties of the rings
presented in the preceding paper (DOI: 10.1063/1.3587137).
