Molecular dynamics simulations of the self-diffusion of monodisperse chains oligomers and of their trace diffusion in an entangled polymer host

The apparent analogy between the self-diffusion of linear oligomers, 2 up to 64 monomers, and their trace diffusion in an entangled polymer host of length 256 was investigated by molecular dynamics at constant pressure. Oligomers and polymers were represented by a same generic coarse-grained (bead-spring) model. The scaling relationships of the self-diffusion coefficient, D, and trace diffusion coefficient, DT , with the chain length, N , of the diffusant, written as D ∝ N −α and DT ∝ N , were analyzed for a wide range of temperatures down to the glass transition temperature, Tg. Near Tg, the heterogeneous dynamics was assessed by the self part of the van-Hove distribution function and non-Gaussian parameters. For both self-diffusion and trace diffusion, a scaling obeying to α = 1 was identified at all temperatures and regardless of the oligomer lengths. [to be continued]