Ion specific, thin film confinement effects on conductivity in polymerized ionic liquids.

Journal Article · 23 November 2021 · Macromolecules

DOI:https://doi.org/10.1021/acs.macromol.1c01820· OSTI ID:1880536

Zhao, Qiujie; Bennington, Peter; Nealey, Paul F.; Patel, Shrayesh N.; Evans, Christopher M.

Acrylate-based polymerized ionic liquids (PILs) with ammonium (Am) or imidazolium (Im) cations and tetrafluoroborate (BF4) or bis(trifluoromethanesulfonyl)imide (TFSI) anions were synthesized and spin coated onto gold interdigitated electrodes on silica to investigate nanoconfinement effects on ion transport. The film thickness ranged from 23 to 313 nm. A significant reduction of the in-plane conductivity was observed in some PIL thin films with thickness below 100 nm. Specifically, Am BF4 PIL showed the largest conductivity drop (ca. 50% difference between a 22 nm and a 261 nm film) while Im TFSI PIL showed almost no change under confinement. The difference in conductivity drop is discussed in terms of (i) differences in interfacial layer thickness by fitting a two-layer conductivity model and (ii) potential changes in glass transition temperature (T-g) under confinement, which were estimated using the Vogel-Fulcher-Tammann fits of bulk conductivities. Decreasing film thickness also caused the dielectric loss peaks to shift to lower frequency, indicating that the ion diffusion process slowed under confinement.

• Research Organization: Argonne National Laboratory (ANL)
• Sponsoring Organization: National Science Foundation (NSF); USDOE Office of Science - Office of Basic Energy Sciences - Materials Sciences and Engineering Division
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 1880536
• Journal Information: Macromolecules, Journal Name: Macromolecules Journal Issue: 22 Vol. 54; ISSN 0024-9297
• Country of Publication: United States
• Language: English