Physics – Condensed Matter – Soft Condensed Matter
Scientific paper
2003-12-16
Europhys. Lett. 68, 384-390 (2004)
Physics
Condensed Matter
Soft Condensed Matter
7 pages, 6 figures, submitted to Europhys. Letters
Scientific paper
10.1209/epl/i2003-10314-9
We use an off - lattice bead - spring model of a self - avoiding polymer chain immersed in a 3-dimensional quenched random medium to study chain dynamics by means of a Monte - Carlo (MC) simulation. The chain center of mass mean-squared displacement as a function of time reveals two crossovers which depend both on chain length $N$ and on the degree of Gaussian disorder $\Delta$. The first one from normal to anomalous diffusion regime is found at short time $\tau_1$ and observed to vanish rapidly as $\tau_1 \propto \Delta^{- 11}$ with growing disorder. The second crossover back to normal diffusion, $\tau_2$, scales as $\tau_2 \propto N^{2\nu + 1} f(N^{2-3\nu}\Delta)$ with $f$ being some scaling function. The diffusion coefficient $D_N$ depends strongly on disorder and drops dramatically at a {\em critical dispersion} $\Delta_{c} \propto N^{-2 + 3\nu}$ of the disorder potential so that for $\Delta > \Delta_c$ the chain center of mass is practically frozen.The time-dependent Rouse modes correlation function $C_{p}(t)$ reveals a characteristic plateau at $\Delta > \Delta_c$ which is the hallmark of a non - ergodic regime. These findings agree well with our recent theoretical predictions.
Milchev Andrey
Rostiashvili Vakhtang G.
Vilgis Thomas A.
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