arXiv subjects

O. Durr

Publications and source records attributed to O. Durr.

4 recordsLinked to original sources

arXiv2001

Dynamic percolation theory for particle diffusion in a polymer network

Tracer-diffusion of small molecules through dense systems of chain polymers is studied within an athermal lattice model, where hard core interactions are taken into account by means of the site exclusion principle. An approximate mapping of this problem onto dynamic percolation theory is proposed. This method is shown to yield quantitative results for the tracer correlation factor of the molecules as a function of density and chain length provided the non-Poisson character of temporal renewals in the disorder configurations is properly taken into account.

cond-mat.soft↗

arXiv2001

Model studies of diffusion in glassy and polymer ion conductors

Ion-conducting glasses and polymer systems show several characteristic peculiarities in their composition-dependent diffusion properties and in their dynamic response. First we give a brief review of the current understanding of the ion dynamics in network glasses in terms of stochastic theories. Secondly, a model for PEO(polyethylene-oxide)-based polymer electrolytes is described. The equation of state is calculated from the quasichemical approximation. Using this information together with Monte Carlo simulations of diffusion at constant volume, we obtain constant-pressure results for polymer chain and ion diffusion as a function of ion concentration. This theory allows us to make comparison with experiments which are carried out at constant pressure.

cond-mat↗

arXiv2001

Charge Transport in Polymer Ion Conductors: a Monte Carlo Study

Diffusion of ions through a fluctuating polymeric host is studied both by Monte Carlo simulation of the complete system dynamics and by dynamic bond percolation (DBP) theory. Comparison of both methods suggests a multiscale-like approach for calculating the diffusion coefficients of the ions

cond-mat↗

arXiv2001

Melt viscosities of lattice polymers using a Kramers potential treatment

Kramers relaxation times $τ_{K}$ and relaxation times $τ_{R}$ and $τ_{G}$ for the end-to-end distances and for center of mass diffusion are calculated for dense systems of athermal lattice chains. $τ_{K}$ is defined from the response of the radius of gyration to a Kramers potential which approximately describes the effect of a stationary shear flow. It is shown that within an intermediate range of chain lengths N the relaxation times $τ_{R}$ and $τ_{K}$ exhibit the same scaling with N, suggesting that N-dependent melt-viscosities for non-entangled chains can be obtained from the Kramers equilibrium concept.

cond-mat↗