How does the flexibility of pyrrolidinium cations affect the phase behaviour of 1-alkyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide homologues under stressful conditions?

Yoshihiro Koyama; Kiyoto Matsuishi; Takahiro Takekiyo; Hiroshi Abe; Yukihiro Yoshimura

doi:10.1039/c9cp01730e

How does the flexibility of pyrrolidinium cations affect the phase behaviour of 1-alkyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide homologues under stressful conditions?

Phys Chem Chem Phys. 2019 Jun 7;21(21):11290-11297. doi: 10.1039/c9cp01730e. Epub 2019 May 20.

Authors

Yoshihiro Koyama¹, Kiyoto Matsuishi¹, Takahiro Takekiyo², Hiroshi Abe³, Yukihiro Yoshimura²

Affiliations

¹ Graduate School of Pure and Applied Science, University of Tsukuba, Ibaraki 305-8577, Japan.
² Department of Applied Chemistry, National Defense Academy, 1-10-20, Hashirimizu, Yokosuka, Kanagawa 239-8686, Japan. muki@nda.ac.jp.
³ Department of Materials Science and Engineering, National Defense Academy, 1-10-20, Hashirimizu, Yokosuka, Kanagawa 239-8686, Japan.

PMID: 31106319
DOI: 10.1039/c9cp01730e

Abstract

We conducted high-pressure Raman spectroscopy measurements on a series of 1-alkyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ([Pyr_1n][TFSI], n = 3, 4, 6 and 8) homologues that have different alkyl chain lengths, n, at room temperature. The results showed that all [Pyr_1n][TFSI] samples formed a glassy state in which the glass transition pressure (p_g) slightly increased with an increase in n. This tendency is similar to prior results of high-pressure glass formation of [C_nmim][TFSI], although the p_gs for [Pyr_1n][TFSI] are larger than those for [C_nmim][TFSI] with corresponding n by ∼0.5 GPa. We discuss the local structural changes occurring in [Pyr_1n][TFSI] in view of the conformational changes of the Pyr⁺_1n cation and TFSI^- anion.