Abstract
A reversible, first-order transition separating two liquid phases of a single-component material is a fascinating yet poorly understood phenomenon. Here, we investigate the liquid-liquid transition (LLT) ability of two tetraalkylphosphonium ionic liquids (ILs), [P666,14]Cl and [P666,14][1,2,4-triazolide], using differential scanning calorimetry and dielectric spectroscopy. The latter technique also allowed us to study the LLT at elevated pressure. We found that cooling below 205 K transforms [P666,14]Cl and [P666,14][Trz] from one liquid state (liquid 1) to another (the self-assembled liquid 2), while the latter facilitates the charge transport decoupled from structural dynamics. In contrast to temperature, pressure was found to play an essential role in the self-organization of a liquid 2 phase, resulting in different time scales of charge transport for rapidly and slowly compressed samples. Furthermore, τσ(PLL) was found to be much shorter than τσ(TLL, P=atm), which constitutes the first example of non-isochronal behavior of charge transport at LLT. In turn, dielectric studies through the liquid-glass transition revealed the non-monotonic behavior of τσ at elevated pressure for [P666,14]Cl, while for [P666,14][Trz] τσ(Pg) was almost constant. These results highlight the diversity of liquid-liquid transition features within the class of phosphonium ionic liquids.
Original language | English |
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Pages (from-to) | 5118-5126 |
Number of pages | 9 |
Journal | Journal of Physical Chemistry B |
Volume | 128 |
Issue number | 20 |
DOIs | |
State | Published - May 23 2024 |
Funding
This research was funded in whole by the National Science Centre, Poland [Opus 21, 2021/41/B/ST5/00840]. For the purpose of Open Access, the author has applied a CC-BY public copyright licence to any Author Accepted Manuscript (AAM) version arising from this submission. S.D. and N.M. were supported by the Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences, US Department of Energy.