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Abstract : Off-lattice Monte Carlo simulations of both the single chain structure factor hq and the inter-chain structure factor HDq of flexible polymers in solutions are presented over a wide range of both wavenumber q and concentration c from the dilute to the concentrated regime, for chain lengths up to N = 256. The single chain properties $\{$gyration radius 〈Rg2〉, $hq\}$ are in reasonable agreement with the expected theoretical behavior, showing a crossover from swollen chains $\{\langle R { m g}^2 angle \propto N^{2 u} ,~ hq \propto q^{-1- u}\}$ to Gaussian chains, and the data comply with a scaling description, with a correlation length ξ∝c-ν-3ν-1. However, the inter-chain structure factor HDq disagrees with the corresponding predictions, we find a behaviour HDq∝q-3 only in an intermediate range but this is accidental: rather it is found that HDq smoothly bends over from its saturation value at small q to a behavior close to q-4 at q≈1-ℓ, ℓ being the length of effective bonds. This failure is traced back to the condition that the law HDq∝q-3 should only be observed for ξ-1≪q ≪ℓ-1, a condition reached neither in the simulation nor in experiments. We also compare our results for HDq with the random phase approximation and find strong deviations.





Autor: V. Yamakov A. Milchev K. Binder

Fuente: https://hal.archives-ouvertes.fr/



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