High-pressure glass formation of a series of 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide homologues

Yukihiro Yoshimura; Takahiro Takekiyo; Yoshihiro Koyama; Mayumi Takaku; Misaho Yamamura; Natsumi Kikuchi; Daisuke Wakabayashi; Nobumasa Funamori; Kiyoto Matsuishi; Hiroshi Abe; Nozomu Hamaya

doi:10.1039/c7cp06594a

High-pressure glass formation of a series of 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide homologues

Phys Chem Chem Phys. 2017 Dec 20;20(1):199-205. doi: 10.1039/c7cp06594a.

Authors

Yukihiro Yoshimura¹, Takahiro Takekiyo, Yoshihiro Koyama, Mayumi Takaku, Misaho Yamamura, Natsumi Kikuchi, Daisuke Wakabayashi, Nobumasa Funamori, Kiyoto Matsuishi, Hiroshi Abe, Nozomu Hamaya

Affiliation

¹ Department of Applied Chemistry, National Defense Academy, 1-10-20, Hashirimizu, Yokosuka, Kanagawa 239-8686, Japan. [email protected].

PMID: 29199750
DOI: 10.1039/c7cp06594a

Abstract

We investigated the stability of the liquid phase of a series of 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C_nmim][TFSI]) homologues with different alkyl chain lengths for 3 ≤ n ≤ 10 at room temperature. We found that all [C_nmim][TFSI] samples (n = 3-10) formed a glassy state when pressure was applied. Intriguingly, the glass transition pressure (p_g) slightly increases up to n = 5, reaches a plateau at n ≧ 8, and increases again at n = 10. This is completely different from the high-pressure glass formation of [C_nmim][BF₄], where the p_g decreases as n increases. We discussed the local structural changes occurring in [C_nmim][TFSI] in view of the conformational changes of the cation and anion, and small-angle X-ray scattering data. It seems that [C_nmim][TFSI] is resistant to external pressure and retains its local liquid structure by conformational adjustments of the cation and anion.