Non-gaussian effects in the cage dynamics of polymers

TL;DR

This study explores how non-Gaussian effects influence cage dynamics and structural relaxation in polymers, revealing universal behavior and the significance of non-Gaussian parameters across different physical states.

Contribution

It demonstrates a universal collapse of cage vibration amplitude and relaxation time, and discusses the role of non-Gaussian effects in polymer cage dynamics.

Findings

Cage vibration amplitude and relaxation time collapse on a universal curve.

Non-Gaussian parameters are significant from ballistic to Rouse regimes.

Universal behavior observed across various temperatures, densities, and chain lengths.

Abstract

The correlation between the fast cage dynamics and structural relaxation is investigated in a model polymer system. It is shown that the cage vibration amplitude, as expressed by the Debye-Waller factor, and the relaxation time $\tau_\alpha$ collapse on a single universal curve with a simple analytic form when the temperature, the density, the chain length and the monomer-monomer interaction potential are changed. For the physical states with the same $\tau_\alpha$ coincidence of the mean-square displacement, the intermediate scattering function and the non-Gaussian parameter is observed in a wide time window spanning from the ballistic regime to the onset of the Rouse dynamics driven by the chain connectivity. The role of the non-Gaussian effects is discussed.