Diffusion of rigid rodlike polymer in isotropic solutions studied by dissipative particle dynamics simulation

Dissipative particle dynamics (DPD) was employed to simulate the diffusion of rigid rodlike polymers in isotropic solutions. In a dilute solution range, the simulated diffusion behavior is in good agreement with that as described by the Kirkwood theory. In a semi-dilute range, the simulation shows that the DPD model adopting soft repulsive interactions can effectively reproduce the entanglement effect on both rotational and translational diffusions. The rotational diffusion coefficient Dr obeys the asymptotic scaling law Dr ∼ (νL3)−2 (ν is the number of polymers per volume and L is the polymer length) for the large νL3, which corresponds to formation of a completely enclosed tube in the Doi-Edwards theory. The parallel translational diffusion coefficient D‖ decreases with ν increase, which can be attributed to the friction effect of surrounding medium. The perpendicular translational diffusion coefficient D⊥ decays more drastically with ν increase, which is caused by the topological constraint.