# Dynamics of Polymer Rings in Ring-Linear Blends by Neutron Spin Echo Spectroscopy

## TL;DR

This study uses neutron spin echo spectroscopy to explore how polymer rings behave in mixtures with linear polymers.

## Contribution

The research reveals a dynamic crossover in ring polymer motion as the concentration of linear polymers increases.

## Key findings

- At high ring volume fraction, ring dynamics resemble local reptation despite weaker constraints.
- Blend viscosity peaks at ϕR = 0.5, coinciding with a shift in ring motion.
- For ϕR ≤ 0.35, ring motion is dominated by the linear polymer matrix.

## Abstract

We present a microscopic
investigation of the polyethylene-oxide
(PEO) ring dynamics in symmetric ring-linear blends with a molecular
weight of 40 kg/mol over the full concentration range. Applying neutron
spin echo (NSE) spectroscopy on samples containing a fraction of labeled
rings, we observe the internal ring dynamics and its modifications
as a function of ring volume fraction ϕR. With increasing
linear composition, a dynamic cross over from self-similar ring-like
relaxation to local reptation-like dynamics is observed. At ϕR = 0.5, where the blend viscosity exhibits its maximum, the
spectral shapes change from ring- to local reptation-type dynamics,
even though the enacted constraints are weaker than those in the linear
melt. For ϕR ≤ 0.35, the ring motion is completely
enslaved by the linear host.