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

Area of Science:

• Polymer Physics
• Materials Science
• Rheology

Background:

• Understanding polymer dynamics in blends is crucial for material properties.
• Polyethylene oxide (PEO) blends with ring and linear architectures present unique topological challenges.
• Previous studies have explored linear polymer blends, but ring-linear blend dynamics remain less understood.

Purpose of the Study:

• To investigate the microscopic dynamics of polyethylene oxide (PEO) rings in symmetric ring-linear blends.
• To determine how ring dynamics are influenced by varying ring volume fractions (ϕ_R).
• To explore the transition in relaxation mechanisms from ring-like to reptation-like behavior.

Main Methods:

• Microscopic investigation using neutron spin echo (NSE) spectroscopy.
• Utilized blends of PEO rings and linear PEO chains with a molecular weight of 40 kg/mol.
• Analyzed samples across the full concentration range of ring and linear components.

Main Results:

• Observed a dynamic crossover from self-similar ring-like relaxation to local reptation-like dynamics with increasing linear PEO concentration.
• At a ring volume fraction of 0.5, spectral shapes shifted to reptation-type dynamics despite weaker topological constraints.
• Ring motion was found to be completely enslaved by the linear host for ring volume fractions ≤ 0.35.

Conclusions:

• The dynamics of PEO rings are significantly altered by the presence of linear PEO chains.
• A transition in relaxation mechanisms occurs, influenced by the concentration of linear chains and topological constraints.
• The linear host effectively dictates ring dynamics at lower ring volume fractions.