Synthesis, Thermal Stability, and Ionic Conductivity of Phenyl-Extended Viologen Ditriflate Salts: Tailoring Properties via Oxyethylene Chain Length

Authors

• Seonghyeok L. Cox, University of Nevada, Las Vegas
• Emily Moon, University of Nevada, Las Vegas
• Si L. Chen, University of Nevada, Las Vegas
• David King, University of Nevada, Las Vegas
• Haesook Han, University of Nevada, Las Vegas
• Pradip K. Bhowmik, University of Nevada, Las Vegas
• Calvin Ng Yi Bin, Universiti Malaya
• Thamil Selvi Velayutham, Universiti Malaya
• Alfonso Martinez-Felipe, University of Aberdeen

Document Type

Article

Publication Date

8-23-2026

Publication Title

ASC Omega

First page number:

1

Last page number:

34

Abstract

Six new phenyl-extended viologen salts with oxyethylene groups paired with triflate anions (OTF) have been synthesized using anionic ring-opening and ring-closing reactions (ANRORC) and metathesis reactions with LiOTf salts. The salts, which contain terminal oxyethylene chains of varying lengths ((CH₂CH₂O)_n, n = 1, 2, 3, 4, 5, and 7), are named PEOn-OTF. These materials exhibit a fluorescence response and possess high thermal stability, with processing windows up to approximately 300 °C, as confirmed by thermogravimetric analysis. While samples with short chain lengths (n = 1, 2, and 3) undergo crystallization observed via differential scanning calorimetry, longer chains seem to restrict molecular packing, resulting in amorphous materials (n ≥ 4). Conductivity was studied via dielectric analysis, including an innovative approach to monitor dielectric relaxations through the imaginary component of the complex conductivity. Amorphous samples with long oxyethylene terminal chains display the highest direct current conductivity (σ_dc ∼ 10^–3.5 S·cm^–1 at 110 °C), which is of merit for organic media, but lower than that reported for trifluoromethylsulfonylimide (TFSI) analogues. Our detailed study of relaxations hints at the existence of strong correlations between morphology, dielectric response, and ion transport dynamics, which will be further explored in the near future.

Keywords

Electrical Conductivity; Salts; Electrolytes; Solvents; Thermodynamic Properties

Disciplines

Fluid Dynamics | Materials Chemistry

File Format

PDF

File Size

3500 KB

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

Creative Commons License

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Repository Citation

Cox, S. L., Moon, E., Chen, S. L., King, D., Han, H., Bhowmik, P. K., Yi Bin, C. N., Velayutham, T. S., Martinez-Felipe, A. (2026). Synthesis, Thermal Stability, and Ionic Conductivity of Phenyl-Extended Viologen Ditriflate Salts: Tailoring Properties via Oxyethylene Chain Length. ASC Omega 1-34.
http://dx.doi.org/10.1021/acsomega.6c03901