Dynamics of polymers in elongational flow investigated by inelastic neutron scattering

TL;DR

This study investigates how high molecular weight polymers behave at the nanoscale under elongational flow using neutron spin-echo, revealing anisotropic mobility and weak structural correlations along the chains.

Contribution

It provides new insights into the nanoscale fluctuation dynamics of polymers under non-equilibrium flow conditions using inelastic neutron scattering.

Findings

Polymer mobility becomes highly anisotropic under flow.

Enhanced mobility observed perpendicular to flow direction.

Weak structural correlation along chains at ~17 Å.

Abstract

The nanoscale fluctuation dynamics of semi dilute high molecular weight polymer solutions of Polyethylenoxide (PEO) in D2O under non-equilibrium flow conditions were studied by the neutron spin-echo technique. The sample cell was in contraction flow geometry and provided a pressure driven flow with a high elongational component that stretched the polymers most efficiently. The experiments suggest that the mobility on the scale of a few monomers, comparable to the Kuhn segment length, becomes highly anisotropic and is enhanced perpendicular to the flow direction. Diffraction data show a weak structural correlation along the chains on a length scale of about 17 Angstroems, which might be related to the Kuhn length in this system.