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@ARTICLE{Renier:473734,
author = {Renier, Olivier and Bousrez, Guillaume and Yang, Mei and
Hölter, Milena and Mallick, Bert and Smetana, Volodymyr and
Mudring, Anja-Verena},
title = {{D}eveloping design tools for introducing and tuning
structural order in ionic liquids},
journal = {CrystEngComm},
volume = {23},
number = {8},
issn = {1466-8033},
address = {London},
publisher = {RSC},
reportid = {PUBDB-2022-00214},
pages = {1785 - 1795},
year = {2021},
abstract = {Ionic liquids (ILs) are receiving growing interest as
highly tunable, multifunctional materials. Remarkably for
liquids, they tend to display a high level of structural
order. This structural order may even lead to the formation
of mesophases such as liquid crystals (LCs). Imidazolium
compounds are by far the most popular ILs, because they
offer a widely versatile platform for property tuning. To
investigate what is driving structural order in
imidazolium-based ILs a series of asymmetrical
1-dodecyl-2-methyl-3-alkylimidazolium bromides,
[C$_{12}$C$_1$C$_n$im][Br] with n = 0–12 have been
synthesized, fully characterized and their structures and
properties compared with the analogous
1-dodecyl-3-alkylimidazolium as well as the 1,2,3-triazolium
bromides. The aim is to examine the influence of the
replacement of the most acidic 2-H proton on the imidazolium
head group by methylation on the properties and structure of
ILs. For all compounds, except for compounds with butyl- and
hexyl-chains as well as the protonated species, mesophase
formation can be observed. Obviously, the simple presence of
long alkyl chains such as dodecyl (a design concept
frequently put forward in the literature) is not sufficient
to support mesophase formation alone. Rather, for the
formation of a liquid crystalline phase, a balance between
attractive van der Waals forces, hydrogen bonds, and
electrostatic interactions is required. Data from
temperature-dependent small-angle X-ray scattering (SAXS)
and polarizing optical microscopy (POM) suggest three
different cation conformations for the studied
[C$_{12}$C$_1$C$_n$im][Br]: cations with 0 ≤ n ≤ 4
exhibit a near-linear conformation; for 5 ≤ n ≤ 10 a
V-shape is adopted, and for n = 11 or 12 a U-shape is found.
We demonstrated that the structural possibility for an
interdigitation of the long chains is an influential factor
for the formation of a mesophase.},
cin = {DOOR ; HAS-User},
ddc = {540},
cid = {I:(DE-H253)HAS-User-20120731},
pnm = {899 - ohne Topic (POF4-899) / FS-Proposal: I-20100011
(I-20100011)},
pid = {G:(DE-HGF)POF4-899 / G:(DE-H253)I-20100011},
experiment = {EXP:(DE-H253)D-A2-20150101 / EXP:(DE-H253)D-BW4-20150101},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000623435900009},
doi = {10.1039/D0CE01672A},
url = {https://bib-pubdb1.desy.de/record/473734},
}