Tunable Nanoscale Structure via Divalent Ion Identity in Charged-Neutral Polymer Blends

Area of Science:

• Materials Science
• Polymer Chemistry
• Electrochemistry

Background:

• Charged-neutral polymer blends are promising battery electrolytes due to enhanced ion transport and stability.
• Theoretical models suggest electrostatic interactions can stabilize nanostructures, but experimental evidence is limited.
• Controlling nanoscale morphology is crucial for optimizing electrolyte performance.

Purpose of the Study:

• To investigate the impact of divalent cation identity (Mg2+ vs. Ca2+) on the nanoscale morphology of charged-neutral polymer blends.
• To explore the relationship between ion solvation and blend miscibility/phase behavior.
• To demonstrate the tunability of nanostructure formation via counterion selection.

Main Methods:

• Preparation of charged-neutral polymer blends using poly(ethylene oxide) (PEO) and ion-containing polymers with Mg2+ or Ca2+ counterions.
• Differential scanning calorimetry (DSC) to analyze thermal properties and miscibility.
• Small-angle X-ray scattering (SAXS) to probe nanoscale morphology and ordering.

Main Results:

• Increasing ion-containing polymer concentration suppressed PEO crystallinity, indicating enhanced miscibility.
• Mg2+ containing blends exhibited microphase separation and short-ranged nanostructure ordering at high concentrations.
• Ca2+ containing blends remained homogeneous, showing a single glass-transition temperature and featureless SAXS, due to stronger PEO solvation.

Conclusions:

• Charged-neutral polymer blends can undergo microphase separation, confirming theoretical predictions.
• Divalent counterion identity is a critical design parameter for controlling nanoscale morphology in these blends.
• This provides a pathway for tailoring polymer blend electrolytes for advanced battery applications.