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

Zhongmou Chao; Brian P Radka; Ke Xu; Garrison M Crouch; Donghoon Han; David B Go; Paul W Bohn; Susan K Fullerton-Shirey

doi:10.1002/smll.201802023

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

Small. 2018 Sep;14(39):e1802023. doi: 10.1002/smll.201802023. Epub 2018 Aug 17.

Authors

Zhongmou Chao¹, Brian P Radka¹, Ke Xu¹, Garrison M Crouch², Donghoon Han², David B Go^{2

3}, Paul W Bohn^{2

4}, Susan K Fullerton-Shirey^{1

5}

Affiliations

¹ Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA, 15213, USA.
² Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN, 46556, USA.
³ Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN, 46556, USA.
⁴ Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, 46556, USA.
⁵ Department of Electrical and Computer Engineering, University of Pittsburgh, Pittsburgh, PA, 15213, USA.

Abstract

Materials with reconfigurable optical properties are candidates for applications such as optical cloaking and wearable sensors. One approach to fabricate these materials is to use external fields to form and dissolve nanoscale conductive channels in well-defined locations within a polymer. In this study, conductive atomic force microscopy is used to electrochemically form and dissolve nanoscale conductive filaments at spatially distinct points in a polyethylene glycol diacrylate (PEGDA)-based electrolyte blended with varying amounts of ionic liquid (IL) and silver salt. The fastest filament formation and dissolution times are detected in a PEGDA/IL composite that has the largest modulus (several GPa) and the highest polymer crystal fraction. This is unexpected because filament formation and dissolution events are controlled by ion transport, which is typically faster within amorphous regions where polymer mobility is high. Filament kinetics in primarily amorphous and crystalline regions are measured, and two different mechanisms are observed. The formation time distributions show a power-law dependence in the crystalline regions, attributable to hopping-based ion transport, while amorphous regions show a normal distribution. The results indicate that the timescale of filament formation/dissolution is determined by local structure, and suggest that structure could be used to tune the optical properties of the film.

Keywords: conductive-AFM; ionic liquid; polymer electrolyte; silver filament.

Abstract

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