Internal dissipation of a polymer

TL;DR

This paper investigates the internal dissipation mechanisms in a single polymer chain without solvent, revealing that damping behavior is close to Kelvin damping and persists even with strong internal potentials, affecting polymer dynamics.

Contribution

It introduces a model of polymer internal dissipation without solvent, showing damping behavior and oscillations depending on internal potential strength and wavelength.

Findings

Damping is similar to Kelvin damping but not identical.

Underdamped oscillations occur for long wavelengths even with strong dihedral barriers.

Internal dissipation influences polymer dynamics significantly.

Abstract

The dynamics of flexible polymer molecules are often assumed to be governed by hydrodynamics of the solvent. However there is considerable evidence that internal dissipation of a polymer contributes as well. Here we investigate the dynamics of a single chain in the absence of solvent to characterize the nature of this internal friction. We model the chains as freely hinged but with localized bond angles and 3-fold symmetric dihedral angles. We show that the damping is close but not identical to Kelvin damping, which depends on the first temporal and second spatial derivative of monomer position. With no internal potential between monomers, the magnitude of the damping is small for long wavelengths and weakly damped oscillatory time dependent behavior is seen for a large range of spatial modes. When the size of the internal potential is increased, such oscillations persist, but the damping becomes larger. However underdamped motion is present even with quite strong dihedral barriers for long enough wavelengths.