Microscopic muon dynamics in the polymer electrolyte poly(ethylene oxide).

Area of Science:

• Materials Science
• Condensed Matter Physics
• Polymer Science

Background:

• Poly(ethylene oxide) (PEO) exhibits complex dynamics crucial for its applications.
• Understanding proton (H^{+}) mobility in polymers is essential for energy storage and other technologies.
• Muons (Mu^{+}) serve as light analogs to probe microscopic dynamics in materials.

Purpose of the Study:

• To investigate the microscopic dynamics of protons in PEO using positive muons.
• To determine the hopping dynamics and activation energy of Mu^{+} in PEO.
• To correlate Mu^{+} dynamics with the glass transition temperature of PEO.

Main Methods:

• Muon spin relaxation (μSR) spectroscopy in zero and transverse magnetic fields.
• Implantation of positive muons (Mu^{+}) into PEO samples.
• Temperature-dependent measurements from 140 K to 310 K.

Main Results:

• Mu^{+} hopping in PEO occurs in the fast fluctuation limit between 140 K and 310 K.
• Muon spin relaxation rates are sensitive to the glass transition of PEO.
• Activated hopping of Mu^{+} was observed above the glass transition with an activation barrier of 122±1 meV.
• Radiolytic electron diffusion explains the temperature dependence of diamagnetic muon polarization.

Conclusions:

• Mu^{+} spin relaxation is a valuable probe for studying polymer dynamics, particularly near the glass transition.
• The study provides quantitative insights into proton-like mobility in PEO.
• Muon spectroscopy offers a unique perspective on charge carrier diffusion in polymers.