Direct-Write Formation and Dissolution of Silver Nanofilaments in Ionic Liquid-Polymer Electrolyte Composites

Area of Science:

• Materials Science
• Nanotechnology
• Polymer Science

Background:

• Reconfigurable optical materials are crucial for advanced applications like optical cloaking and wearable sensors.
• Fabricating these materials often involves creating and dissolving nanoscale conductive channels within polymers using external fields.

Purpose of the Study:

• To investigate the electrochemical formation and dissolution of nanoscale conductive filaments in polyethylene glycol diacrylate (PEGDA)-based electrolytes.
• To understand the influence of local polymer structure on filament kinetics and ion transport.

Main Methods:

• Conductive atomic force microscopy (CAFM) was employed to electrochemically form and dissolve nanoscale conductive filaments.
• PEGDA-based electrolytes with varying amounts of ionic liquid (IL) and silver salt were synthesized and tested.
• Filament kinetics were measured in both amorphous and crystalline regions of the polymer composite.

Main Results:

• The fastest filament formation and dissolution times were observed in PEGDA/IL composites with high modulus and significant polymer crystal fraction.
• Unexpectedly, faster kinetics occurred in crystalline regions, contrary to the expectation that amorphous regions facilitate ion transport.
• Distinct ion transport mechanisms were identified: power-law dependence (hopping transport) in crystalline regions and normal distribution in amorphous regions.

Conclusions:

• The timescale of conductive filament formation and dissolution is strongly determined by the local nanostructure of the polymer composite.
• These findings suggest that controlling the polymer's microstructure can be a viable strategy for tuning the reconfigurable optical properties of materials.