Polymerizable ionic liquids for solid-state polymer electrolytes

Article abstract of DOI:10.3390/molecules24020324

Eight new polymerizable ammonium-TFSI ionic liquids were synthesized and characterized with respect to an application in energy storage devices. The ionic liquids feature methacrylate or acrylate termination as polymerizable groups. The preparation was optimized to obtain the precursors and ionic liquids in high yield. All products were characterized by NMR and IR spectroscopy. Phase transition temperatures were obtained by DSC analysis. Density, viscosity and ionic conductivity of the ionic liquids were compared and discussed. The results reveal that the length of attached alkyl groups as well as the methyl group at the polymerizable function have significant influences on the ionic liquids physicochemical properties. Ionic conductivity values vary between 0.264 mS cm^?1 for [C₂N_A,22]TFSI and 0.080 mS cm^?1 for [C₈N_MA,22]TFSI at 25 ^?C. Viscosity values are within a range of 0.762 Pa s for [C₂N_A,22]TFSI and 1.522 Pa s for [C₆N_MA,22]TFSI at 25 ^?C.

Full text of DOI:10.3390/molecules24020324

molecules
Article
Polymerizable Ionic Liquids for Solid-State
Polymer Electrolytes
Robert Löwe 1,2, Thomas Hanemann 1,2 and Andreas Hofmann 1,
*
1
Institute for Applied Materials, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1,
D-76344 Eggenstein-Leopoldshafen, Germany; robert.loewe@kit.edu (R.L.); thomas.hanemann@kit.edu (T.H.)
Department of Microsystems Engineering, University of Freiburg, Georges-Köhler-Allee 102,
D-79110 Freiburg, Germany
2
*
Correspondence: andreas.hofmann2@kit.edu; Tel.: +49-721-608-25920
ꢀꢁꢂꢀꢃꢄꢅꢆꢇ
ꢀꢁꢂꢃꢄꢅꢆ
Received: 20 December 2018; Accepted: 13 January 2019; Published: 17 January 2019
Abstract: Eight new polymerizable ammonium-TFSI ionic liquids were synthesized and characterized
with respect to an application in energy storage devices. The ionic liquids feature methacrylate or acrylate
termination as polymerizable groups. The preparation was optimized to obtain the precursors and ionic
liquids in high yield. All products were characterized by NMR and IR spectroscopy. Phase transition
temperatures were obtained by DSC analysis. Density, viscosity and ionic conductivity of the ionic
liquids were compared and discussed. The results reveal that the length of attached alkyl groups as
well as the methyl group at the polymerizable function have significant influences on the ionic liquids
physicochemical properties. Ionic conductivity values vary between 0.264 mS cm−1 for [C2NA,22]TFSI
and 0.080 mS cm−1 for [C8NMA,22]TFSI at 25 ◦C. Viscosity values are within a range of 0.762 Pa s for
[C2NA,22]TFSI and 1.522 Pa s for [C6NMA,22]TFSI at 25 ◦C.
Keywords: polymerizable ionic liquids; property-structure relationship; conductivity; viscosity; density
1. Introduction
Ionic liquids (ILs) possess a wide range of applications, being employed in CO2 adsorption [
catalysis [ ] or as solvents [ ]. They are promising candidates in drug design [ ] and drug delivery
systems [ ] due to their high biological activity [ ] and the possibility to combine bioactive cations
with bioactive anions, e.g., the salicylate (Sal) ionic liquid (IL) [EMIM-OSal][Sal] [ ]. Within the field
of energy storage systems, such as lithium ion batteries, ionic liquids are discussed as alternatives
to conventional electrolytes [ ]. Remarkable properties for electrochemical applications are low
1],
2
3
4
5
6
7
8
flammability, low vapor pressure, a broad electrochemical window (ca. 4–6 V) [8] and a high tunability
of properties by structural variations and usage of IL mixtures.
For particular applications, immobilization of the ionic liquids is beneficial. In terms of drug
design, a solid dosage form can lead to a higher convenience of products. In lithium ion batteries
the electrolyte can move freely within the cell and thus lead to unwanted side reactions. A common
example is the reactions of the aluminum current collector with bis(trifluoromethanesulfonyl)imide
(TFSI) containing ionic liquids [9]. This type of degradation mechanism can be avoided if the electrolyte
is fixed between the electrodes. Different approaches to immobilize ionic liquids are known. It is
relatively easy to distinguish between materials in which the ILs are absorbed within a matrix [10] and
materials in which the ionic liquids are fixed by covalent bonding [11,12]. The latter is an interesting
approach for transferring the outstanding properties of ionic liquids to solid materials and covalent
networks. In our research, we focus on ILs that feature acrylate or methacrylate functional groups
for this particular purpose. Polymerization and reactions such as the alkene hydrothiolation are
candidates to link the ILs to a covalent network.
Molecules 2019, 24, 324; doi:10.3390/molecules24020324
www.mdpi.com/journal/molecules

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A common method for the preparation of ammonium ionic liquids is a reaction pathway with two
steps. In a first step, the tertiary amine is converted in a quaternary ammonium salt by Menshutkin
reaction [13
e.g., PF6, BF4 or TFSI [15
,
14]. Within the second step, the halogen anion is exchanged for an organic anion,
17]. Preparation of ionic liquids starting from the polymerizable amines
–
2-(diethylamino)ethyl methacrylate (DEAEMA) and 2-(diethylamino)ethyl acrylate (DEAEA) is rarely
described in the literature [18]. However, there are few reports on the synthesis of the halogen
precursors by Menshutkin reaction [13,14]. It is known that the turnover of DEAEA to the desired
precursor lowers drastically when the quaternization reaction is performed with alkyl bromides
containing more than two carbon atoms. Regarding to the literature, yields decrease from 62% (DEAEA
+ C2H5Br) [19] to 13% (DEAEA + C4H9Br) [19] and 2.1% (DEAEA + C6H9Br) [18]. This is consistent
with the general trend that is found for the reaction rate constant of SN2 reactions which decreases
with increasing size of the alkylating agent [20]. In terms of reaction mechanism, the Menshutkin
reaction can be seen as a special type of SN2 reaction [21]. In comparison to other SN2 type reactions,
the reactions rate is promoted by increasing solvent polarity [21]. Synthesis of similar ionic liquids
starting from the methyl substituted amines 2-(dimethylamino)ethyl methacrylate (DMAEMA) or
2-(dimethylamino)ethyl acrylate (DMAEA) were described by several authors [18,22]. In the literature,
alkyl bromides and acetone or chloroform were used as reagent and solvent, respectively, thus resulting
in high yields for the precursors, e.g., 89% for [C4NMA,11]Br [22] and 82.6% for [C6NMA,11]Br [18].
In contrast to the earlier mentioned precursors, the yields for the quaternization of DMAEMA and
DMAEA are still reasonable for alkyl substituents with more than two carbon atoms.
For application in energy storage systems the relationship between structure variations and
fundamental properties such as glass transition temperature, viscosity and ionic conductivity are of
great interest. Two common models for data interpretation are the Arrhenius equation (1) and the
Vogel–Fulcher–Tammann (VFT) Equation (2)
η = AηeE /RT
;
σ = Aσe−E /RT
(1)
(2)
η
σ
η = Aηek /(T−T )
;
σ = Aσe−k /(T−T )
η
σ
0
0
with Aη and Aσ as the viscosity and conductivity at infinite temperature, Eη and Eσ as flow and conductivity
activation energies, the ideal gas constant R, the temperature T, kη and kσ as constants and T0 as ideal glass
transition temperature [23]. In the literature the ideal parameter T0 is described as temperature where free
volume disappears so that cooperative movement of chain segments, as well as motion related phenomena
such as diffusion or migration of molecules and ions becomes impossible [23]. Due to kinetic reasons,
this state cannot be reached within a limited time scale and T0 is found to be lower than experimentally
measured values for Tg [23]. Correlation of the different fundamental properties offers further possibilities
for analysis and interpretation of the experimental results. Scaling the Arrhenius plot to experimentally
measured Tg values leads to the Arrhenius plot of fragilities or so-called Angell plot. Thereby, glass
builders are classified as strong or fragile. The liquid structure of fragile materials responses very sensitive to
temperature changes, which is associated with a relative narrow glass transition temperature range. Strong
glass builders response in an opposite way [24,25]. Another interpretation is made by the Walden plot.
In 1906 Paul Walden released his underlying empirically found relationship, that the product of viscosity
of a solvent and its molar conductivity is constant [26]. Within the plot, experimental data are related to a
line of an ideal electrolyte solution, which commonly is a 1-molar KCl solution. In the field of ionic liquids,
the position of the ILs line is compared to the ideal line to classify the ILs in superionic liquids, good ILs
and poor ILs concerning the decoupling of one charge carrier from the viscosity determined structure [27].
In the case of superionic the ILs line is located above the ideal line, which leads to the interpretation that one
charge carrier species is partially decoupled from the viscous bulk. Slightly below and directly on the ideal
line, ILs are classified as good ionic liquids featured by a quasi-lattice state and a low ionicity. The more the
ILs line is below the ideal line, the more this state is shifted to direct ion pairing and higher ionicities [27].

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In this study, we focus on the systematic preparation and characterization of polymerizable
ionic liquids starting from DEAEMA and DEAEA. First, we describe the optimization of the reaction
conditions to achieve almost quantitative precursor yields even for steric demanding alkyl chains and
the adapted anion exchange. Subsequently, the characterization of the IL products is presented with
respect to an application of the ionic liquids in energy storage systems. Structure-property relationships
of the monomeric ILs are analyzed and their adaptability on polymerized ionic liquids are discussed.
2. Results and Discussion
2.1. Synthesis
Eight new ionic liquids were prepared in a two-step synthesis, shown in Figure 1. In the first step
the amines DEAEMA and DEAEA were converted into quaternary ammonium bromide or iodide salts
using the Menshutkin reaction [13,14]. In a following metathesis reaction, the halogen anions were
exchanged by the organic anion bis(trifluoromethanesulfonyl)imide (TFSI).
Figure 1. Reaction scheme for the preparation of the IL and notation.
Compared to the dimethyl substituted ammonium ionic liquids known from literature [11,22],
two ethyl substituents are attached to the nitrogen atom in DEAEMA and DEAEA. This variation
is associated with a higher steric hindrance at the amine function. We found that the yields of the
quaternization reaction to bromide precursors are much lower when comparable reaction conditions from
the literature were used with DEAEMA and DEAEA as starting materials. With increasing lengths of
alkyl chains, the yields dropped drastically and fell below a reasonable level for C4-C8 rests. In order
to achieve the quaternary ammonium salts in high yields, different reaction conditions were applied.
Table 1 gives an overview of selected reactions. To avoid declining yields with increasing chain lengths,
the reaction time and temperature were increased, thus leading to a partial degradation of the double
bonds. Referring to Daoudi et al., the reaction of DEAEMA with nBuBr in dichloromethane was supposed
to proceed almost quantitatively when the mixture was heated 8 h under reflux [28]. Applying similar
conditions (16 h of reflux), the reaction failed and no product was obtained. Yields were significantly
enhanced by the combination of alkyl iodides and acetone as reactants and solvent, respectively, as well as

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by the usage of acetonitrile as solvent when alkyl bromides were used. In SN2 type reactions iodide is the
better leaving group compared to bromide, due to its lower basicity. Solvents with higher polarity affect
the Menshutkin reaction positively [21]. Accordingly, the combination of acetonitrile as solvent and alkyl
iodides as reactants led to almost quantitative yields, while the excess of alkyl halides was reduced.
Table 1. Selected reaction conditions and yields of the intermediate products.
Product
Solvent
Reaction Time Temperature Alkyl Halide Excess
Yield
◦
[C2NMA,22]Br
[C4NMA,22]Br
[C6NMA,22]Br
[C4NMA,22]Br
Acetone
Acetone
Acetone
CH2Cl2
6 d
6 d
11 d
16 h
47.0 C
1.4
1.4
1.4
1.2
60.7%
7.0%
◦
47.0 C
◦
56.0 C
51.5% a
0.0%
◦
39.6 C
◦
[C6NMA,22]I
[C6NMA,22]Br
Acetone
Acetonitrile
5 d
6 d
56.0 C
1.4
1.4
66.3%
54.0%
◦
56.0 C
◦
[C2NMA,22]I
[C4NMA,22]I
[C6NMA,22]I
Acetonitrile
Acetonitrile
Acetonitrile
1 d
3 d
3 d
45.0 C
1.1
1.1
1.1
96.4%
97.5%
95.9%
◦
60.0 C
◦
60.0 C
a 1H NMR spectroscopy revealed that approx. 25% of the double bonds were degraded during the reaction.
All synthesized ammonium bromide compounds are strongly hygroscopic and feature a high
solubility in water. Hence, using bromide intermediates, the anions exchange was executed in an aqueous
solution from which the desired product precipitates. The synthesized iodide intermediates show a
significantly lower hygroscopy and are therefore easier to handle under ambient conditions. A drawback
compared to bromides is the accompanied decrease in water solubility, which makes a metathesis in
pure water difficult for most of the precursor iodides. Instead the meth(acrylate) iodides were dissolved
in acetone and added dropwise to an aqueous LiTFSI solution from which the IL phase precipitated
immediately. The attempt to remove undesirable residues by extraction of the ionic liquids with chloroform
and washing the organic phase with water points out to be impractical. The solubility of the ILs in
chloroform is strongly limited and two organic phases appeared. The high viscosity and adhesion on the
glass surface of the ionic liquid enriched phases, makes an effective separation from the aqueous phase
almost impossible, when a separation funnel is used. In contrast, washing the IL monomers directly several
times with purified water and decanting the aqueous phase, removed the remaining acetone and lithium
halide salts from the products in an easy and effective manner. Table 2 gives an overview of the achieved
yields concerning the two-step synthesis with ammonium iodide salts as intermediate products.
Table 2. Particular yields of all reaction steps and resulting overall yields for the ILs.
Precursor
Yield [%]
Ionic Liquid
Yield [%]
Overall Yield [%]
[C2NMA,22]I
[C4NMA,22]I
[C6NMA,22]I
[C8NMA,22]I
96.4
97.5
95.9
93.2
[C2NMA,22]TFSI
[C4NMA,22]TFSI
[C6NMA,22]TFSI
[C8NMA,22]TFSI
90.7
88.8
91.7
90.7
87.4
86.6
87.9
84.5
[C2NA,22]I
[C4NA,22]I
[C6NA,22]I
[C8NA,22]I
98.5
96.6
96.1
89.4
[C2NA,22]TFSI
[C4NA,22]TFSI
[C6NA,22]TFSI
[C8NA,22]TFSI
85.0
80.5
89.5
89.3
83.7
77.8
86.0
79.8
To accelerate the preparation of the ILs, a one-pot synthesis for [C2NMA,22]TFSI was carried out,
by way of example. Without optimization of reaction conditions, a total yield of 66% was achieved,
making the one-pot synthesis easily accessible to industrial scales.
It was found in the study that for long-term-storage the ionic liquids must be handled with an
inhibitor to avoid any polymerization. An appropriate inhibitor which can be used when oxygen is
present in the sample is MEHQ (Hydroquinone monomethyl ether) [29].

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2.2. Density
◦
◦
Density values of all prepared TFSI-ionic liquids were measured between 5 C and 60 C. The resulting
data are plotted in Figure 2 and fitted to a linear function y = m x + n. The calculated parameters are
×
presented in Table 3. Density values of the acrylates are higher than the values of the methacrylate ILs
with respect to the same alkyl chain lengths. With an increasing length of the attached alkyl group, density
values decrease. Longer chains and the variation from acrylate to methacrylate groups lead to increased
bulkiness and steric demand of the molecules, which is expressed in lower density values.
Figure 2. Density values of the synthesized TFSI-Ionic Liquids.
Table 3. Parameters from linear fit of density values (y = m × x + n).
−3
IONIC Liquid
m
n/g·cm
−4
−4
−4
−4
−4
−4
−4
−4
[C2NMA,22]TFSI
[C4NMA,22]TFSI
[C6NMA,22]TFSI
[C8NMA,22]TFSI
[C2NA,22]TFSI
[C4NA,22]TFSI
[C6NA,22]TFSI
[C8NA,22]TFSI
1.40202
1.34746
1.30603
1.27181
1.42503
1.36936
1.32206
1.28568
−8.86882 × 10
−8.70826 × 10
−8.44608 × 10
−8.29652 × 10
−8.76545 × 10
−8.64216 × 10
−8.40463 × 10
−8.18980 × 10
As the linear fitting shows, the lines are almost parallel. The slopes indicate a tendency to flatten with
increasing alkyl chain length. The parameter n shows the differences between the calculated densities at
0 ◦C, which decrease with increasing chain length towards smaller density values. Density values of new
ionic liquids of the same homologous series can be estimated on basis of the presented interpretation.
2.3. Thermal Analysis
DSC analysis was applied to the halogen salts and TFSI-ionic liquids. Data of the melting points
result from a single measurement. For glass transition temperatures the probes were heated twice
from
−
150 ◦C to 180 ◦C with 10 K min−1. The given Tg values are the values of detected inflection
points of the first occurring glass transition (Tg(L)) for each substance at the first heating curve.
As shown in Figure 3, two second order phase transitions, Tg(L) and Tg(U), appear in DSC
analysis. Tg(L) refers to the conventional glass transition and is therefore labeled as Tg in the further
text. The appearance of Tg(U) might be associated with semi-crystalline, smectic or para-crystalline
phases as discussed in literature for semi-crystalline polymers [30].

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Figure 3. DSC heating curve of [C2NA,22]TFSI which stands exemplary for all synthesized ILs.
Table 4 shows the resulting data of DSC analysis and gives two different values for Tg (Tg(L)).
The Tg,1 value was measured two weeks after synthesis in a single probe analysis. The second
value, Tg,2, is the average glass transition temperature of three probes, which were of the same batch,
but stored eight weeks before DSC analysis was applied. All freshly synthesized ionic liquids were
diluted in acetone (50 wt%) and stored at
removed under vacuum at room temperature within an argon glove box.
−
40 ◦C. Before any analysis, the acetone was completely
The data indicate that the intermediates melting points decrease with increasing length of the
introduced alkyl chains, except [C4NMA,22]I. The acrylate iodides show lower melting points than the
methacrylate iodides. The studied bromid salt intermediates feature higher melting points than the
analogous iodides.
The glass transition temperatures of the ionic liquids tend to decrease with increasing alkyl length.
It is remarkable that the Tg,2 values are in average 4.3 K higher than Tg,1 values. There is evidence that this
observation is due to partial polymerization processes, although the ionic liquids are diluted in acetone
◦
(50 wt%) and stored at
−
40 C. The process of double bond degradation is also seen on the morphology of
the ionic liquids after the acetone is removed. In contrast to freshly prepared ionic liquids, the probes start
to thread after storing them several weeks. For analysis in Arrhenius plot of fragilities Tg,1 values are used
due to the evidence that these values are less influenced by autopolymerization.
Table 4. Melting points (Tm) and glass transition temperatures (Tg) of the products. Standard uncertainties
u for values from this work are u(Tm) = 2 K; u(Tg) = 2 K.
Halogen Intermediate Salt
Ionic Liquid
Entry
Product
Onset [K]
Entry
Product
Tg,1 [K] 1
Tg,2 [K] 2
Standard Deviation 2
s
1
2
3
4
5
6
7
8
9
[C2NMA,22]I
[C4NMA,22]I
[C6NMA,22]I
[C8NMA,22]I
[C2NA,22]I
[C4NA,22]I
[C6NA,22]I
[C8NA,22]I
339.9
353.3
332.9
317.7
330.3
321.2
318.3
291.6
348.4
345.1
339.9
12
13
14
15
16
17
18
19
[C2NMA,22]TFSI
[C4NMA,22]TFSI
[C6NMA,22]TFSI
[C8NMA,22]TFSI
[C2NA,22]TFSI
[C4NA,22]TFSI
[C6NA,22]TFSI
[C8NA,22]TFSI
219.2
216.8
215.2
213.2
211.7
214.5
211.6
212.6
223.0
223.2
220.4
218.4
215.5
218.2
216.1
214.4
0.3
1.2
1.0
0.2
0.9
1.1
0.4
0.6
[C2NMA,22]Br
[C4NMA,22]Br
[C6NMA,22]Br
10
11
1
Measurement two weeks after synthesis and storage at
−
40 ◦C diluted in acetone (50 wt%). Acetone was
2
completely removed under vacuum before measurement. Measurements after eight weeks of storage at same
conditions as before.

Molecules 2019, 24, 324
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2.4. Rheological Behavior
The viscosity of the ionic liquid monomers was studied in two manners. First, a constant
temperature of 20 ◦C and varying shear rates from 1 s−1 to 250 s−1 were applied, resulting in shear
rate independent viscosity for all the prepared ILs (within 1 s−1 to 250 s−1). Second, a temperature
program from 20 ◦C to 100 ◦C at a constant shear rate of 100 s−1 was applied. The dependence of the
viscosity values on the temperature is given in Figure 4.
(a)
(b)
Figure 4. Viscosity values at various temperatures for methacrylate ILs (a) and acrylate ILs (b).
The results reveal that the ethyl-substituted ILs have the lowest viscosity values within the
studied temperature range. Butyl- to octyl-substituted derivates show low divergence in the viscosity
values and temperature dependence and thus, no correlation between the chain lengths and the
viscosity values was found for these derivates. In general, the methacrylate ionic liquids tend to
higher viscosities than the analogous acrylates at same temperatures. The data indicate that bulky
groups within the ILs promote higher viscosity values. Phenomena such as entanglements increase
the internal friction and are most likely to be causal for this observation. Tokuda et al. found the same
property-structure relationship for imidazolium TFSI ionic liquids and correlated it to the influence on
the ionic self-diffusivity [31].
2.5. Electrochemical Characterization
The ionic conductivity of the TFSI ionic liquids was calculated from the corresponding impedance
spectra. The closed, airtight measuring cells for the liquid monomers were assembled inside
an argon-purged glovebox (O2 and H2O < 0.5 ppm). ◦ Electrochemical impedance spectroscopy
◦
experiments were done at temperatures between
−
40 C and 100 C. During the measurements,
the cells were located inside an oven. After the adjusted temperatures reached the desired values,
further 20 min were given to the system before measurement to ensure a steady state. Voltage for
potentiostatic impedance spectroscopy was set to 0.000 V. Amplitudes of 10 mV were applied with
varying frequencies within the range of 100 Hz to 1 MHz. Figure 5 shows the temperature dependency
of the ionic conductivity values. From 100 C to 10 C, the conductivity values decrease logarithmically.
Below 5 ◦C there is an abrupt flatten of the conductivity curves, which indicates a phase transition
within the given temperature range. This is consistent with the appearance of the upper glass transition
temperature, Tg(U), in DSC. Due to the limitation of ionic mobility, the conductivity values strongly
approach σ(Tg) with onset of the upper phase transition.
◦
◦

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There is a significant impact of the structural modifications on the ionic conductivity, showing a
straight structure-property relationship. It was found, that increasing chain lengths of the introduced
alkyl group correlate with lower ionic conductivities. Furthermore, the acrylates show higher
conductivity values than the methacrylate derivates at the same alkyl chain lengths and temperatures.
◦
The conductivities at 25 C ranging from 0.264 mS cm−1 ([C2NA,22]TFSI) down to 0.080 mS cm−1
([C8NMA,22]TFSI), as given in Table 5.
(a)
Figure 5. Ionic conductivity values at various temperatures for methacrylate ILs (a) and acrylate ILs (b).
Table 5. Experimentally measured values of ionic conductivity ( ), density (d), viscosity ( ) and
(b)
κ
η
calculated molar conductivity (
Λ
m) at 25 ◦C and at pressure p = 0.1 MPa. Standard uncertainties u
for values from this work are u(d) = 0.001 g cm−3; u(
η
) = 0.05·η; u(
κ
) = 0.03·κ; u(p) = 5 kPa; u (
Λ
m) =
0.06·Λm; u(Tκ) = 0.1 K; u(Tη) = 0.1 K; u(Td) = 0.01 K (specified temperature during conductivity (Tκ),
density (Td) and viscosity (Tη) measurement).
Ionic Conductivity
Molar Conductivity
−3
Ionic Liquid
Density [g cm
]
Viscosity [Pa s]
−1
−1
]
[mS cm
]
[mS cm2 mol
[C2NMA,22]TFSI
[C4NMA,22]TFSI
[C6NMA,22]TFSI
[C8NMA,22]TFSI
[C2NA,22]TFSI
[C4NA,22]TFSI
[C6NA,22]TFSI
[C8NA,22]TFSI
0.211
0.112
0.093
0.080
0.264
0.136
0.122
0.103
75.7
44.2
39.8
36.8
90.3
51.1
50.3
46.1
2.790
2.537
2.334
2.162
2.920
2.650
2.425
2.241
0.905
1.395
1.522
1.425
0.762
1.477
1.284
1.246
2.6. Analysis of Structure-Property Relationships
The variation between acrylate and methacrylate terminal function as well as the length of the
introduced alkyl chain significantly affect the ionic liquids physicochemical properties. The measured
densities decrease with increasing chain lengths and steric demand of the side chains, to remain the
same trends found for the ionic conductivity on the molar conductivity. Ionic conductivity values
decrease and viscosity values tend to increase with increasing steric demand of the attached side chains.
Similar influences of structural variations on density, rheological behavior and conductivity were
reported in the literature for imidazolium TFSI ILs, indicating a general trend for structure-property
relationship of ionic liquids [31].
Considering the influence of the attached alkyl chains on the conductivity and viscosity values in
Table 5, it turns out that the step from C2 to C4 chains is accompanied with a more pronounced property
change than any other step in chain prolongation. For both homologous series, acrylates and methacrylates,
the ionic conductivity drops almost 50% from C2 to C4 chains, whereas the step from C4 to C8 rests leads
to a decrease in the order of 25% to 30%. The trend found for the viscosity values shows a similar behavior.

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There is a significant increase in viscosity when going from C2 to C4 groups. From C4 to C8 side chains
there is no straight property-structure relationship identifiable and the occurring variations of viscosity
values are much less pronounced than caused by the step from C2 to C4.
Since all studied ionic liquids are featured by the same anion, the variance in the chemico-physical
values is primarily driven by the structural differences of the cations. On one side, longer and
bulkier sidechains lead to a higher steric demand of the molecules on the molecular level, thus
resulting in lower densities. On the other side, higher densities cause stronger intermolecular forces,
concerning anion-cation interactions as well as attractive forces between the organic cations, such as
aliphatic π-interactions. As expected from this consideration, it was found that the glass transition
temperatures tend to decrease with increasing length of the substituted alkyl groups due to higher free
volumes, but contradicts the influence of the methyl group at the double bond. Table 6 shows that
the studied acrylate ILs feature lower glass transition temperatures than the respective methacrylates.
Therefore, it is assumed that the higher steric freedom of the acrylate function without attached methyl
group has a more dominant influence on Tg than stronger electrostatic interactions between the cations.
The introduced alkyl chains are accompanied with an electron donating inductive effect.
Longer alkyl chains will lead to a reduction of charge density at the cationic center. Thus, induce
a more independent mobility of cations and anions and result in a higher ionic conductivity.
Experimentally the opposite observation was made on the ionic conductivity. Therefore, it is stated
that the electrostatic effect of alkyl chains has a negligible impact on the ionic conductivity. The adverse
influence of longer chains on the cations mobility is most likely to limit the conductivity in impedance
spectroscopy experiments.
The influence of the substituents steric demand on the cations mobility can be derived by the
comparison of viscosity values of the different ILs. Figure 6 shows the empirical analysis of the
viscosity values in terms of an Arrhenius plot (equation 1). The data between 20 ◦C and 60 ◦C were
linear fitted and the flow activation energy was calculated within this temperature range. The results
are given in Table 7 and show the same behavior as discussed for the viscosity values.
Table 6.
Comparison of experimentally determined Tg and calculated T0 from VFT fit.
Standard uncertainties u for values from this work are u(Tg) = 2 K.
Ionic Liquid
Tg [K] 1,2
T0 [K] 3
Tg/T0
[C2NMA,22]TFSI
[C4NMA,22]TFSI
[C6NMA,22]TFSI
[C8NMA,22]TFSI
[C2NA,22]TFSI
[C4NA,22]TFSI
[C6NA,22]TFSI
[C8NA,22]TFSI
219.2
216.8
215.2
213.2
211.7
214.5
211.6
212.6
2
201.8
208.7
197.7
200.0
186.8
202.7
193.7
190.6
1.09
1.04
1.09
1.07
1.13
1.06
1.09
1.11
1
Experimentally measured values are provided. The measurement was performed two weeks after synthesis
and storage at
40 ◦C diluted in acetone (50 wt%). Acetone was completely removed under vacuum before
measurement. Values are calculated from VFT fits of ionic conductivity values (Figure 7b).
−
3

Molecules 2019, 24, 324
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Figure 6. Arrhenius fit of viscosity values.
Table 7. Calculated Flow activation energies from Arrhenius fit are shown (20 C–60 C).
◦
◦
−1
]
Ionic Liquid
Eη [kJ mol
[C2NMA,22]TFSI
[C4NMA,22]TFSI
[C6NMA,22]TFSI
[C8NMA,22]TFSI
[C2NA,22]TFSI
[C4NA,22]TFSI
[C6NA,22]TFSI
[C8NA,22]TFSI
54.9 ± 1.5
59.7 ± 1.3
58.1 ± 1.1
56.7 ± 1.0
50.3 ± 1.0
57.1 ± 1.1
54.0 ± 0.9
53.1 ± 0.8
With respect to the experimentally measured glass transition temperatures and the viscosities,
Figure 7a represents the Arrhenius plot of fragility. Due to the analysis, all studied ionic liquids are
classified as fragile. They react sensitive to thermal excitation and thus show a narrow temperature
range of glass transition.
(a)
(b)
Figure 7. (a) Arrhenius plot of fragilities; (b) VFT fit of ionic conductivity values.

Molecules 2019, 24, 324
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Empirical description of ionic conductivity values is done by VFT fit shown in Figure 7b
(Equation (2)). The analysis was initialized by iterative non-linear least squares to give values for
T0 (Table 6). Due to this procedure, the ionic conductivity data fit well to the VFT equation in a
◦
◦
temperature range between 5 C and 100 C. Below this range, conductivity values approach the
conductivity at Tg. As expected, T0 values are below the measured Tg values and Tg/T0 is within the
same range as found for other TFSI-ionic liquids in the literature [23].
The correlation of molar conductivity and viscosity of the studied ionic liquids is plotted in a
Walden plot. Figure 8 shows the resulting linear relationship, which indicates a completely dissociation
of all ions in the system. The data for all ionic liquids are located slightly below the ideal Walden line,
which implies that the charge carriers are coupled to the viscosity determining structure. In terms of
the Walden plot, all products are classified as good ionic liquids. The lines of the studied ILs are very
close to each other, which shows that there are only small differences in ionicities between the ILs.
This supports the already discussed assumption that the strength of cation-anion interactions is not
the causal driving force for the found structure-property relationships.
Regarding the application of the studied ionic liquids in electrolyte systems, acrylates with short
alkyl chains seem to outperform methacrylates and more bulky substituents due to the lower viscosity
and higher conductivity. Although they found similar behaviors for the ionic liquids, Zhang et al.
showed that the polymer of undoped [C7NMA,11]TFSI reveals a higher ionic conductivity than the
[C4NMA,11]TFSI polymer [22]. Therefore, the property-relationships of the pure ILs cannot be directly
transferred on their polymers. Further, additional material properties such as strength and brittleness
of the polymers and the influences of conducting salt and additives must be regarded separately for
particular applications.
Figure 8. Walden plot for the studied TFSI ionic liquids.
In pretests, the monomers were successfully polymerized.
For example, compound
[C2NMA,22]TFSI can be polymerized via UV induced bulk polymerization with 1 mol-% initiator
(Irgacure 651) resulting in hard and brittle glasses. However, a broad range of parameters influences
the polymeric matters properties. Thus, there are many parameters influencing the polymers properties
starting with the general type of chosen polymerization method, type of initiator, initiator concentration
and so on. Additionally, a huge toolbox of analytical methods for characterization, such as DSC,
electrochemical impedance spectroscopy, cyclic voltammetry or size-exclusion chromatography,
is available. With respect to an application in energy storage systems further parameters such as the
type of applied conducting salt, salt concentration or additives come in addition. All these effects
influence the structure and properties of the polymers. The presented results are focusing on the
synthesis and characterization of the polymerizable monomers. In respect of its huge scope, the study
of the polymerized ionic liquid materials will soon be presented separately.

Molecules 2019, 24, 324
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3. Conclusions
In this study, we have synthesized and characterized eight new ionic liquids to improve the
understanding of how structural changes affect the physicochemical properties of ionic liquids.
Reaction conditions were optimized to obtain almost quantitative yields for the yield limiting
quaternization reaction. The study reveals that an increasing side chain length at the ammonium
moiety as well as and methyl group at the acrylate function accompany with increasing viscosity and
◦
decreasing ionic conductivity values. At 25 C the ionic conductivity of the studied ionic liquids varies
−1
−1
between 0.264 mS cm for [C2NA,22]TFSI and 0.080 mS cm and viscosity values between 0.762 Pa s
[C2NA,22]TFSI and 1.522 Pa s [C6NMA,22]TFSI were found. Ionicity of the investigated ionic liquids
shows low diversity in Walden plot. It is therefore assumed that the structure-property relationships
of tetraalkylated ammonium ionic liquids are mainly driven by the steric properties of the cation on
molecular level. It was found that the examined ionic liquids tend to autopolymerize when storing
◦
them diluted in acetone (50 wt%) at
−
40 C. For the permanent usage at ambient conditions and
elevated temperatures an inhibitor system will be required to prevent degradation of the double
bonds. The data reveal that the polymerizable ionic liquids with short sidechains have favorable
properties for an application in ionic conducting materials. Nevertheless, the literature indicate that
the structure-property relationships found for the monomeric ionic liquids cannot be transferred on
their polymers without further investigation.
4. Experimental Section
4.1. Materials
2-(Diethylamino)ethyl
methacrylate
(99%),
2-(diethylamino)ethyl
acrylate
(95%),
bromoethane (98%), 1-bromobutane (99%), 1-bromohexane (
bis(trifluoromethane)sulfonimide lithium salt (99%) were purchased from Sigma-Aldrich (Munich,
≥
99%), phenothiazine (
≥
98%) and
Germany). Iodoethane (98%), 1-iodobutane (98%), 1-iodohexane (98%), 1-iodooctane (98%) and molecular
◦
sieves (3 Å, 8-12 mesh) were received from Acros Organics (Geel, Belgium). Acetone (
≥
98.8%) and diethyl
ether (anhydrous) were purchased from Fisher Scientific (Schwerte, Germany). Water (HPLC grade) and
acetonitrile ( 99.7%; HPLC grade) were purchased from Carl Roth (Karlsruhe, Germany) and Alfa Aesar
(Karlsruhe, Germany), respectively. All chemicals were used as received.
≥
4.2. Measurements
NMR spectra were recorded using an Avance III HD 500 MHz spectrometer (Bruker, Germany) and
ATR-FTIR spectra with a Vertex 70 (Bruker, Germany). Dynamic viscosities of the ILs were measured
with a Gemini HR Nano rheometer (Bohlin, UK) and cone-plate system (CP4/40). For impedance
spectroscopy a Zahner Zennium potentiostat (Zahner, Germany) and TSC 1600 Closed measurement
cells (rhd, Germany) located inside a SH-261 oven (Espec, USA) were applied. The water content
of the ILs was measured by Karl Fischer-titration with a KF Coulometer 831 (Metrohm, Germany)
◦
coupled with a KF Thermoprep 860 oven (Metrohm, Germany) at 180 C and flow rate of 150 mL
min−1. Melting points and glass transition temperatures were measured by DSC analysis using a
DSC 204 F1 Phoenix (Netzsch, Germany) with temperature programs between
−
150 ◦C and 180 ◦C
and heating rates of 10 K min−1. Elemental analysis was carried out with a vario MICRO (Elementar,
Germany) and a SARTORIUS M2P was used as analytical balance. Densities of ionic liquids were
measured with a DMA 4500 M (Anton Paar, Austria) between 0.0 ◦C and 60.0 ◦C.
4.3. Synthesis
All solid products are stored in amber glass flasks inside an argon-filled glovebox. All TFSI ionic
liquids are diluted to 50 wt% in acetone under argon and stored under exclusion of light at
After removing the acetone, the ILs show less than 10 ppm water in Karl Fischer-titration. For synthesis
and washing of ionic liquids deionized water (HPLC grade) was used without exceptions.
−
30 ◦C.

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N,N,N-Triethyl-N-[2-(methacryloyloxy)ethyl]ammonium bromide ([C2NMA,22]Br)
A mixture of 2-(diethylamino)ethyl methacrylate (DEAEMA, 10.99 g, 59.32 mmol) and a excess
of bromoethane (9.24 g, 84.84 mmol) in 30 mL acetone was stirred under argon-oxygen atmosphere
◦
(80:20% v/v) at 47 C for 6 days and under exclusion of UV irradiation. All volatile components
were removed under reduced pressure. The precipitate was washed with ethyl ether and dried under
vacuum for 10 h. The product was received as a white powder (10.61 g, 60.8% yield). M.p.: 111.2 ◦C;
1H NMR (500 MHz, CDCl3):
δ
(ppm) 1.45 (t, 9H, CH3); 1.95 (s, 3H, CH3); 3.64 (q, 6H, CH2); 3.97 (t, 2H,
CH2);); 4.76 (t, 2H, CH2); 5.68 (s, 1H, CH2); 6.12 (s, 1H, CH2); 13C NMR (125 MHz, CDCl3):
(ppm) 8.3
(CH3); 18.3 (CH2); 54.4 (CH2); 56.0 (CH2); 57.8 (CH2); 127.5 (CH2); 135.1 (C); 166.4 (C=O); IR (cm−1):
2979 (C-H); 1717 (C=O); 1638 (C=C); 1479 as(CH2); 1390 s(CH3); 1320 (CH2); 1298 (C-O); 1168
ν(C-O); 1002 δ(CH2); 947 δ(C-H); 784 δ(CH2);
δ
ν
ν
ν
δ
δ
δ
ν
N-Butyl-N,N-diethyl-N-[2-(methacryloyloxy)ethyl]ammonium bromide ([C4NMA,22]Br)
A mixture of 2-(diethylamino)ethyl methacrylate (DEAEMA, 11.12 g, 60.00 mmol) and a excess of
1-bromobutane (11.51 g, 84.00 mmol) in 30 mL acetone was stirred under argon-oxygen atmosphere
(80:20% v/v) under reflux for 11 days and under exclusion of UV irradiation. All volatile components
were removed under reduced pressure. The precipitate was washed with ethyl ether and dried under
vacuum for 24 h. The product was received as a white powder (9.49 g, 49.1% yield). M.p.:107.9 ◦C;
1H NMR (500 MHz, CDCl3):
1.96 (s, 3H, CH3); 3.44 (m, 2H, CH2); 3.67 (q, 4H, CH2); 4.01 (t, 2H, CH2); 4.69 (t, 2H, CH2); 5.70 (s, 1H,
CH2); 6.14 (s, 1H, CH2); 13C NMR (125 MHz, CDCl3):
(ppm) 8.4 (CH3); 13.7 (CH3); 18.3 (CH3); 19.8
(CH2); 24.1 (CH2); 55.4 (CH2); 56.6 (CH2); 57.8 (CH2); 58.9 (CH2); 127.5 (CH2); 135.1 (C); 166.5 (C=O);
IR (cm−1): 2963
(C-H); 1721 (C=O); 1640 (C=C); 1457 as(CH2); 1399 s(CH3); 1300 (C-O); 1159
(C-O); 1013 (CH2); 934 (C-H); 788 (CH2); Elemental analysis calcd (%) for C14H28BrNO2: C, 52.18;
δ (ppm) 1.02 (t, 3H, CH3); 1.47 (m, 8H, CH3, CH2); 1.76 (m, 2H, CH2);
δ
ν
ν
ν
δ
δ
ν
ν
δ
δ
δ
H, 8.76; N, 4.35. Found (%): C, 51.59; H, 8.49; N, 4.41.
N,N-Diethyl-N-hexyl-N-[2-(methacryloyloxy)ethyl]ammonium bromide ([C6NMA,22]Br)
A mixture of 2-(diethylamino)ethyl methacrylate (DEAEMA, 5.59 g, 30.02 mmol) and a excess of
1-bromohexane (6.93 g, 42.00 mmol) in 15 mL acetonitrile was stirred under argon-oxygen atmosphere
◦
(80:20% v/v) at 56 C for 6 days and under exclusion of UV irradiation. All volatile components
were removed under reduced pressure. The precipitate was washed with ethyl ether and dried under
vacuum. The product was received as a white powder (5.67 g, 53.9% yield). M.p.:102.7 ◦C; 1H NMR
(500 MHz, CDCl3):
1.93 (s, 3H, CH3); 3.40 (m, 2H, CH2); 3.64 (q, 4H, CH2); 3.97 (t, 2H, CH2); 4.65 (t, 2H, CH2); 5.66 (s,
1H, CH2); 6.11 (s, 1H, CH2); 13C NMR (125 MHz, CDCl3):
(ppm) 8.3 (CH3); 16.9 (CH3); 18.3 (CH3);
22.2 (CH2); 22.4 (CH2); 26.1 (CH2); 31.2 (CH2); 55.0 (CH2); 56.6 (CH2); 57.9 (CH2); 59.0 (CH2); 127.4
(CH2); 135.1 (C); 166.4 (C=O); IR (cm−1): 2928
(C-H); 1717 (C=O); 1640 (C=C); 1446 as(CH2); 1399
s(CH3); 1298 (C-O); 1163 (C-O); 1009 (CH2); 945 (C-H); 813 (CH2); Elemental analysis calcd (%)
δ (ppm) 0.87 (t, 3H, CH3); 1.33 (m, 6H, CH2); 1.43 (t, 6H, CH3); 1.74 (m, 2H, CH2);
δ
ν
ν
ν
δ
δ
ν
ν
δ
δ
δ
for C16H32BrNO2: C, 54.85; H, 9.21; N, 4.00. Found (%): C, 54.73; H, 9.17; N, 4.01.
N,N,N-Triethyl-N-[2-(methacryloyloxy)ethyl]ammonium iodide ([C2NMA,22]I)
A mixture of 2-(diethylamino)ethyl methacrylate (DEAEMA, 27.789 g, 150.0 mmol), a slight
excess of iodoethane (25.735 g, 165.0 mmol) and phenothiazine (0.6 g, 3.0 mmol) as inhibitor in 15 mL
◦
acetonitrile was stirred under argon atmosphere at 45 C for 24 h and under exclusion of UV irradiation.
All volatile components were removed under reduced pressure. The precipitate was washed with
ethyl ether and dried under vacuum. The product was received as a white powder (49.32 g, 96.4%
yield). M.p.: 102.7 ◦C; 1H NMR (500 MHz, acetone-D6):
δ
(ppm) 1.46 (t, 9H, CH3); 1.96 (s, 3H, CH3);
3.73 (q, 6H, CH2); 4.02 (t, 2H, CH2); 4.72 (t, 2H, CH2); 5.74 (s, 1H, CH2); 6.14 (s, 1H, CH2); 13C NMR
(125 MHz, acetone-D6): (ppm) 7.6 (CH3); 17.6 (CH2); 53.9 (CH2); 55.6 (CH2); 58.0 (CH2); 126.1
δ

Molecules 2019, 24, 324
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(CH2); 135.8 (C); 166.1 (C=O); IR (cm−1): 2974
ν
(C-H); 1719
ν
(C=O); 1635
ν
(C=C); 1457
δas(CH2); 1397
δ
s(CH3); 1300
ν
(C-O); 1165
ν
(C-O); 1000
δ(CH2); 949
δ(C-H); 782 δ(CH2); Elemental analysis calcd (%)
for C12H24INO2: C, 42.24; H, 7.09; N, 4.10. Found (%): C, 42.24; H, 7.11; N, 4.10.
N-Butyl-N,N-diethyl-N-[2-(methacryloyloxy)ethyl]ammonium iodide ([C4NMA,22]I)
A mixture of 2-(diethylamino)ethyl methacrylate (DEAEMA, 27.789 g, 150.0 mmol), a slight
excess of 1-iodobutane (30.363 g, 165.0 mmol) and phenothiazine (0.6 g, 3.0 mmol) as inhibitor in
15 mL acetonitrile was stirred under argon atmosphere at 60 ◦C for 3 days and under exclusion of
UV irradiation. All volatile components were removed under reduced pressure. The precipitate was
washed with ethyl ether and dried under vacuum. The product was received as a slightly yellowish
powder (54.02 g, 97.5% yield). M.p.: 116.1 ◦C; 1H NMR (500 MHz, acetone-D6):
δ (ppm) 1.02 (t, 3H,
CH3); 1.49 (m, 8H, CH3, CH2); 1.90 (m, 2H, CH2); 1.96 (t, 3H, CH3); 3.62 (m, 2H, CH2); 3.75 (q, 4H,
CH2); 4.00 (m, 2H, CH2); 4.72 (m, 2H, CH2); 5.75 (t, 1H, CH2); 6.15 (s, 1H, CH2); 13C NMR (125 MHz,
acetone-D6):
57.9 (CH2); 58.2 (CH2); 126.0 (CH2); 135.8 (C); 166.0 (C=O); IR (cm−1): 2963
(C=C); 1458 as(CH2); 1401 s(CH3); 1300 (C-O); 1163 (C-O); 1013 (CH2); 960
δ
(ppm) 7.4 (CH3); 13.0 (CH3); 17.5 (CH3); 19.5 (CH2); 23.7 (CH2); 54.4 (CH2); 56.0 (CH2);
(C-H); 1724 (C=O); 1640
(C-H); 813 (CH2);
ν
ν
ν
δ
δ
ν
ν
δ
δ
δ
Elemental analysis calcd (%) for C14H28INO2: C, 45.53; H, 7.64; N, 3.79. Found (%): C, 45.48; H, 7.64;
N, 3.73.
N,N-Diethyl-N-hexyl-N-[2-(methacryloyloxy)ethyl]ammonium iodide ([C6NMA,22]I)
A mixture of 2-(diethylamino)ethyl methacrylate (DEAEMA, 27.789 g, 150.0 mmol), a slight
excess of 1-iodohexane (34.992 g, 165.0 mmol) and phenothiazine (0.6 g, 3.0 mmol) as inhibitor in
15 mL acetonitrile was stirred under argon atmosphere at 60 ◦C for 3 days and under exclusion of
UV irradiation. All volatile components were removed under reduced pressure. The precipitate was
washed with ethyl ether and dried under vacuum. The product was received as a white powder
(57.18 g, 95.9% yield). M.p.: 95.7 ◦C; 1H NMR (500 MHz, acetone-D6):
δ (ppm) 0.91 (t, 3H, CH3); 1.39
(m, 6H, CH2); 1.49 (t, 6H, CH3); 1.92 (m, 2H, CH2); 2.00 (s, 3H, CH3); 3.62 (m, 2H, CH2); 3.75 (q, 4H,
CH2); 4.01 (m, 2H, CH2); 4.72 (s, 2H, CH2); 5.75 (s, 1H, CH2); 6.15 (s, 1H, CH2); 13C NMR (125 MHz,
acetone-D6):
54.4 (CH2); 56.0 (CH2); 57.9 (CH2); 58.4 (CH2); 126.0 (CH2); 135.8 (C); 166.0 (C=O); IR (cm−1): 2954
(C-H); 1721 (C=O); 1640 (C=C); 1456 as(CH2); 1403 s(CH3); 1296 (C-O); 1157 (C-O); 1060
(CH2); 1011 (CH2); 936 (C-H); 808 (CH2); Elemental analysis calcd (%) for C16H32INO2: C, 48.37;
δ (ppm) 7.4 (CH3); 13.3 (CH3); 17.5 (CH3); 21.7 (CH2); 22.2 (CH2); 25.8 (CH2); 31.1 (CH2);
ν
ν
ν
δ
δ
ν
ν
δ
δ
δ
δ
H, 8.12; N, 3.53. Found (%): C, 48.43; H, 8.13; N, 3.50.
N,N-Diethyl-N-[2-(methacryloyloxy)ethyl]-N-octylammonium iodide ([C8NMA,22]I)
A mixture of 2-(diethylamino)ethyl methacrylate (DEAEMA, 27.789 g, 150.0 mmol), a slight
excess of 1-iodooctane (39.621 g, 165.0 mmol) and phenothiazine (0.6 g, 3.0 mmol) as inhibitor in
15 mL acetonitrile was stirred under argon atmosphere at 75 ◦C for 3 days and under exclusion of
UV irradiation. All volatile components were removed under reduced pressure. The precipitate was
washed with ethyl ether and dried under vacuum. The product was received as a white powder
(59.47 g, 93.2% yield). M.p.: 80.5 ◦C; 1H NMR (500 MHz, acetone-D6):
δ (ppm) 0.88 (m, 3H, CH3);
1.32 (m, 6H, CH2); 1.46 (m, 10H, CH3, CH2); 1.91 (m, 2H, CH2); 1.96 (s, 3H, CH3); 3.64 (m, 2H, CH2);
3.76 (q, 4H, CH2); 4.06 (s, 2H, CH2); 4.73 (s, 2H, CH2); 5.74 (s, 1H, CH2); 6.15 (s, 1H, CH2); 13C NMR
(125 MHz, acetone-D6): δ (ppm) 7.9 (CH3); 13.6 (CH3); 17.7 (CH3); 22.0 (CH2); 22.4 (CH2); 26.2 (CH2);
29.0 (CH2); 31.6 (CH2); 54.6 (CH2); 56.3 (CH2); 58.2 (CH2); 58.6 (CH2); 126.1 (CH2); 135.9 (C); 166.1
(C=O); IR (cm−1): 2928
1154 (C-O); 1060 (CH2); 1009
C18H36INO2: C, 50.82; H, 8.53; N, 3.29. Found (%): C, 50.51; H, 8.48; N, 3.27.
ν
(C-H); 1724
ν
(C=O); 1640
ν
(C=C); 1454
δas(CH2); 1399 δs(CH3); 1291 ν(C-O);
ν
δ
δ(CH2); 936
δ(C-H); 806
δ(CH2); Elemental analysis calcd (%) for

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N-[2-(Acryloyloxy)ethyl]-N,N,N-triethylammonium iodide ([C2NA,22]I)
A mixture of 2-(diethylamino)ethyl acrylate (DEAEA, 25.686 g, 150.0 mmol), a slight excess of
iodoethane (25.735 g, 165.0 mmol) and phenothiazine (0.6 g, 3.0 mmol) as inhibitor in 15 mL acetonitrile
◦
was stirred under argon atmosphere at 45 C for 24 h and under exclusion of UV irradiation. All volatile
components were removed under reduced pressure. The precipitate was washed with ethyl ether
and dried under vacuum. The product was received as a white powder (48.33 g, 98.5% yield). M.p.:
93.1 ◦C; 1H NMR (500 MHz, acetone-D6):
δ
(ppm) 1.47 (t, 9H, CH3); 3.72 (q, 6H, CH2); 3.97 (m, 2H,
CH2); 4.73 (s, 2H, CH2); 6.01 (dd, 1H, CH2); 6.24 (m, 1H, CH); 6.44 (dd, 1H, CH2); 13C NMR (125 MHz,
acetone-D6): (ppm) 7.3 (CH3); 53.8 (CH2); 55.4 (CH2); 57.5 (CH2); 127.8 (CH); 131.6 (CH2); 164.8
(C=O); IR (cm−1): 2979
(C-H); 1719 (C=O); 1624 (C=C); 1461 as(CH2); 1401 s(CH3); 1271 (C-O);
1183 (C-O); 1086 (CH2); 1064 (CH2); 1020 (CH2); 998 (C-H); 960 (C-H); 808 (CH2); Elemental
δ
ν
ν
ν
δ
δ
ν
ν
δ
δ
δ
δ
δ
δ
analysis calcd (%) for C11H22INO2: C, 40.38; H, 6.78; N, 4.28. Found (%): C, 40.61; H, 6.78; N, 4.52.
N-[2-(Acryloyloxy)ethyl]-N-butyl-N,N-diethylammonium iodide ([C4NA,22]I)
A mixture of 2-(diethylamino)ethyl acrylate (DEAEA, 15.945 g, 93.1 mmol), a slight excess of
1-iodobutane (18.849 g, 102.4 mmol) and phenothiazin◦e (0.6 g, 3.0 mmol) as inhibitor in 15 mL
acetonitrile was stirred under argon atmosphere at 75 C for 2 days and under exclusion of UV
irradiation. All volatile components were removed under reduced pressure. The precipitate was
washed with ethyl ether and dried under vacuum. The product was received as a slightly yellowish
powder (31.96 g, 96.6% yield). M.p.: 84.0 ◦C; 1H NMR (500 MHz, acetone-D6):
δ (ppm) 1.02 (t, 3H,
CH3); 1.47 (m, 8H, CH3, CH2); 1.89 (m, 2H, CH2); 3.63 (m, 2H, CH2); 3.75 (q, 4H, CH2); 4.01 (m, 2H,
CH2); 4.74 (s, 2H, CH2); 6.02 (m, 1H, CH2); 6.24 (m, 1H, CH); 6.44 (m, 1H, CH2); 13C NMR (125 MHz,
acetone-D6):
58.3 (CH2); 127.8 (CH); 131.7 (CH2); 164.8 (C=O); IR (cm−1): 2965
1459 as(CH2); 1406 s(CH3); 1260 (C-O); 1188 (C-O); 1071 (CH2); 1022
(CH2); Elemental analysis calcd (%) for C13H26INO2: C, 43.95; H, 7.38; N, 3.94. Found (%): C, 44.18;
δ
(ppm) 7.6 (CH3); 13.1 (CH2); 19.5 (CH2); 23.8 (CH2); 54.5 (CH2); 56.1 (CH2); 57.7 (CH2);
(C-H); 1724 (C=O); 1622 (C=C);
(CH2); 965 (C-H); 806
ν
ν
ν
δ
δ
ν
ν
δ
δ
δ
δ
H, 7.38; N, 4.00.
N-[2-(Acryloyloxy)ethyl]-N,N-diethyl-N-hexylammonium iodide ([C6NA,22]I)
A mixture of 2-(diethylamino)ethyl acrylate (DEAEA, 25.686 g, 150.0 mmol), a slight excess
of 1-iodohexane (34.992 g, 165.0 mmol) and phenothiazine (0.6 g, 3.0 mmol) as inhibitor in 15 mL
◦
acetonitrile was stirred under argon atmosphere at 60 C for 3 days and under exclusion of UV
irradiation. All volatile components were removed under reduced pressure. The precipitate was
washed with ethyl ether and dried under vacuum. The product was received as a white powder
(55.26 g, 96.1% yield). M.p.: 81.1 ◦C; 1H NMR (500 MHz, acetone-D6):
δ (ppm) 0.91 (t, 3H, CH3); 1.41
(m, 6H, CH2); 1.48 (t, 6H, CH3); 1.92 (m, 2H, CH2); 3.62 (q, 2H, CH2); 3.74 (s, 4H, CH2); 3.99 (m, 2H,
CH2); 4.74 (s, 2H, CH2); 6.02 (m, 1H, CH2); 6.24 (m, 1H, CH); 6.45 (m, 1H, CH2); 13C NMR (125 MHz,
acetone-D6):
56.0 (CH2); 57.6 (CH2); 58.5 (CH2); 127.8 (CH); 131.6 (CH2); 164.8 (C=O); IR (cm−1): 2954
(C=O); 1624 (C=C); 1456 (CH2); 1406 s(CH3); 1263 (C-O); 1188 (C-O); 1071 (CH2); 1022
971 (C-H); 936 (C-H); 806 (CH2); Elemental analysis calcd (%) for C15H30INO2: C, 47.00; H, 7.89; N,
δ
(ppm) 7.4 (CH3); 13.3 (CH2); 21.8 (CH2); 22.2 (CH2); 25.8 (CH2); 31.1 (CH2); 54.4 (CH2);
(C-H); 1721
(CH2);
ν
ν
ν
δ
δ
ν
ν
δ
δ
δ
δ
δ
3.65. Found (%): C, 47.05; H, 7.89; N, 3.66.
N-[2-(Acryloyloxy)ethyl]-N,N-diethyl-N-octylammonium iodide ([C8NA,22]I)
A mixture of 2-(diethylamino)ethyl acrylate (DEAEA, 25.686 g, 150.0 mmol), a slight excess
of 1-iodooctane (39.621 g, 165.0 mmol) and phenothiazine (0.6 g, 3.0 mmol) as inhibitor in 15 mL
◦
acetonitrile was stirred under argon atmosphere at 60 C for 3 days and under exclusion of UV
irradiation. All volatile components were removed under reduced pressure. The precipitate was
washed with ethyl ether and dried under vacuum. The product was received as a white powder

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◦
1
(55.16 g, 89.4% yield). M.p.: 54.4 C; H NMR (500 MHz, acetone-D6):
δ
(ppm) 0.89 (t, 3H, CH3);
1.33 (m, 6H, CH2); 1.47 (m, 10H, CH3, CH2); 1.92 (m, 2H, CH2); 3.62 (m, 2H, CH2); 3.75 (q, 4H, CH2);
4.01 (m, 2H, CH2); 4.74 (s, 2H, CH2); 6.01 (m, 1H, CH2); 6.24 (m, 1H, CH); 6.45 (m, 1H, CH2); 13C
NMR (125 MHz, acetone-D6):
28.9 (CH2); 31.6 (CH2); 54.5 (CH2); 56.1 (CH2); 57.7 (CH2); 58.5 (CH2); 127.8 (CH); 131.6 (CH2); 164.8
(C=O); IR (cm−1): 2926
(C-H); 1728 (C=O); 1640 (C=C); 1454 as(CH2); 1406 s(CH3); 1267 (C-O);
1188 (C-O); 1075 (CH2); 1009 (CH2); 978 (C-H); 804 (CH2); Elemental analysis calcd (%) for
δ (ppm) 7.5 (CH3); 13.5 (CH2); 21.9 (CH2); 22.4 (CH2); 26.2 (CH2);
ν
ν
ν
δ
δ
ν
ν
δ
δ
δ
δ
C17H34INO2: C, 49.64; H, 8.33; N, 4.40. Found (%): C, 49.46; H, 8.22; N, 3.35.
N,N,N-Triethyl-N-[2-(methacryloyloxy)ethyl]ammonium bis(trifluoromethanesulfonyl)imide
([C2NMA,22]TFSI)
The respective intermediate [C2NMA,22]I (22.180 g, 65.0 mmol) was dissolved in water (15 mL) and
added to a solution of LiTFSI (19.501 g, 67.9 mmol) in water (15 mL). The ionic liquid precipitated instantly
and the mixture was stirred further for 10 min at room temperature. The aqueous top layer was removed
and the remaining organic layer was washed six times with water (40 mL), respectively. No iodide ions
were detected in the last washing water by AgNO3 solution. The ionic liquid was diluted in acetone
(40 mL) and dried over molecular sieves (10 g, 3 Å) for 24 h. The solution was filtrated (PTFE, 0.2 µm)
and the acetone removed under reduced pressure. The ionic liquid was stirred at room temperature
under vacuum (6 mbar) for 2 days to give the pure product as colorless oil (29.16 g, 90.7%yield). 1H NMR
(500 MHz, CDCl3):
(m, 2H, CH2); 5.62 (m, 1H, CH2); 6.03 (s, 1H, CH2); 13C NMR (125 MHz, CDCl3):
(CH2); 54.0 (CH2); 55.3 (CH2); 57.3 (CH2); 120.1 (q, CF3); 127.3 (CH2); 135.1 (C); 166.4 (C=O); IR (cm−1):
2996 (C-H); 1726 (C=O); 1638 (C=C); 1457 as(CH2); 1399 s(CH3); 1349 (SO2); 1179 (C-O); 1135
(S=O); 1053 (S=O); 1002 (CH2); 742 s (CF3); 654 (SNS); 614 a(SO2); Elemental analysis calcd (%) for
δ
(ppm) 1.28 (t, 9H, CH3); 1.87 (s, 3H, CH3); 3.32 (q, 6H, CH2); 3.53 (m, 2H, CH2); 4.45
δ
(ppm) 7.3 (CH3); 18.0
ν
ν
ν
δ
δ
ν
ν
ν
ν
δ
δ
δ
δ
C14H24F6N2O6S2: C, 34.01; H, 4.89; N, 5.67. Found (%): C, 34.11; H, 4.80; N, 5.73.
One-pot synthesis of [C2NMA,22]TFSI
DEAEMA (3.149 g, 17.0 mmol) and 1-iodoethane (2.917 g, 18.7 mmol) were added to a solution of
LiTFSI (5.100 g, 17.8 mmol) in acetonitrile (5 mL). The mixture was stirred at elevated temperature (45 ◦C)
for 16 h. All volatile components were removed under reduced pressure. The remaining oily phase was
washed with water (120 mL in total) in six portions. The IL phase was dissolved in acetone (15 mL) and the
solution was dried over molecular sieves (2.5 g, 3 Å) for 3 days. The solution was filtrated (PTFE, 0.2 µm)
and the acetone was removed under reduced pressure. The ionic liquid was stirred at room temperature
under vacuum (6 mbar) to give the pure product as colorless oil (5.56 g, 66.2% yield).
N-Butyl-N,N-diethyl-N-[2-(methacryloyloxy)ethyl]ammonium bis(trifluoromethanesulfonyl)imide
([C4NMA,22]TFSI)
The respective intermediate [C4NMA,22]I (24.003 g, 65.0 mmol) was suspended in water (30 mL)
and the supernatant water was added to a solution of LiTFSI (19.501 g, 67.9 mmol) in water (15 mL).
The undissolved intermediate salt was solved in acetone (15 mL) and added dropwise to the aqueous
phase. The ionic liquid precipitated instantly and the mixture was stirred for 10 min at room
temperature. Further processing was realized as described above for [C2NMA,22]TFSI to give the
1
product as colorless oil (30.17 g, 88.8% yield). H NMR (500 MHz, CDCl3):
δ (ppm) 0.94 (t, 3H, CH3);
1.30 (t, 6H, CH3); 1.36 (q, 2H, CH2); 1.62 (m, 2H, CH2); 1.90 (s, 3H, CH3); 3.18 (m, 2H, CH2); 3.35 (q, 4H,
CH2); 3.57 (m, 2H, CH2); 4.47 (m, 2H, CH2); 5.64 (s, 1H, CH2); 6.06 (s, 1H, CH2); 13C NMR (125 MHz,
CDCl3):
(CH2); 58.4 (CH2); 119.8 (q, CF3); 127.2 (CH2); 135.0 (C); 166.4 (C=O); IR (cm−1): 2970
(C=O); 1638 (C=C); 1459 as(CH2); 1349 (SO2); 1181 (C-O); 1135 (S=O); 1053 (S=O); 949
788 (CH2); 742 s (CF3); 614 (SNS); Elemental analysis calcd (%) for C16H28F6N2O6S2: C, 36.78; H,
5.40; N, 5.36. Found (%): C, 37.10; H, 5.26; N, 5.37.
δ
(ppm) 7.4 (CH3); 13.3 (CH3); 18.0 (CH3); 19.4 (CH2); 23.5 (CH2); 54.5 (CH2); 55.8 (CH2); 57.2
(C-H); 1724
(C-H);
ν
ν
ν
δ
ν
ν
ν
ν
δ
δ
δ
δ

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N,N-Diethyl-N-hexyl-N-[2-(methacryloyloxy)ethyl]ammonium bis(trifluoromethanesulfonyl)imide
([C6NMA,22]TFSI)
The respective intermediate [C6NMA,22]I (26.74 g, 65.0 mmol) was dissolved in acetone (40 mL)
and added dropwise to a solution of LiTFSI (19.501 g, 67.9 mmol) in water (40 mL). The ionic liquid
precipitated instantly and the mixture was stirred for 10 min at room temperature. Further processing
was realized as described above for [C2NMA,22]TFSI to give the product as colorless oil (32.81 g, 91.7%
1
yield). H NMR (500 MHz, CDCl3):
δ (ppm) 0.85 (t, 3H, CH3); 1.30 (m, 12H, CH3, CH2); 1.63 (m, 2H,
CH2); 1.90 (s, 3H, CH3); 3.17 (m, 2H, CH2); 3.36 (q, 4H, CH2); 3.57 (m, 2H, CH2); 4.47 (s, 2H, CH2);
5.64 (s, 1H, CH2); 6.06 (s, 1H, CH2); 13C NMR (125 MHz, CDCl3):
(ppm) 7.3 (CH3); 13.7 (CH3); 18.0
δ
(CH3); 21.6 (CH2); 22.3 (CH2); 25.7 (CH2); 30.9 (CH2); 54.4 (CH2); 55.8 (CH2); 57.2 (CH2); 58.6 (CH2);
119.8 (q, CF3); 127.2 (CH2); 135.0 (C); 166.3 (C=O); IR (cm−1): 2963 ν(C-H); 2932 ν(C-H); 2864 ν(C-H);
1724
ν
(C=O); 1638
ν
(C=C); 1459
δas(CH2); 1399
δ
s(CH3); 1348 (SO2); 1181
ν
ν(C-O); 1135 ν(S=O); 1055
ν
(S=O); 949
δ(C-H); 788
δ(CH2); 742
δ
s
(CF ); 654
δ(SNS); 616 δa(SO2); Elemental analysis calcd (%) for
3
C18H32F6N2O6S2: C, 39.27; H, 5.86; N, 5.09. Found (%): C, 39.48; H, 5.74; N, 5.07.
N,N-Diethyl-N-[2-(methacryloyloxy)ethyl]-N-octylammonium bis(trifluoromethanesulfonyl)imide
([C8NMA,22]TFSI)
The IL was prepared accordingly to the procedure described above for [C6NMA,22]TFSI starting
from [C8NMA,22]I (27.65 g, 65.0 mmol) in acetone (40 mL) and LiTFSI (19.501 g, 67.9 mmol) in water
1
(40 mL). The product was received as colorless oil (34.11 g, 90.7% yield). H NMR (500 MHz, CDCl3):
δ
(ppm) 0.87 (t, 3H, CH3); 1.27 (m, 6H, CH3); 1.33 (m, 10H, CH2); 1.65 (s, 2H, CH2); 1.93 (s, 3H, CH3); 3.20
(m, 2H, CH2); 3.38 (q, 4H, CH2); 3.59 (m, 2H, CH2); 4.50 (m, 2H, CH2); 5.67 (s, 1H, CH2); 6.09 (s, 1H,
CH2); 13C NMR (125 MHz, CDCl3):
δ
(ppm) 7.4 (CH3); 14.0 (CH3); 18.0 (CH3); 21.7 (CH2); 22.5 (CH2);
26.1 (CH2); 28.9 (CH2); 31.5 (CH2); 54.5 (CH2); 55.8 (CH2); 57.2 (CH2); 58.6 (CH2); 119.8 (q, CF3); 127.2
(CH2); 135.0 (C); 166.4 (C=O); IR (cm−1): 2959
(C-H); 2932 (C-H); 2857 (C-H); 1726 (C=O); 1638
(C=C); 1461 as(CH2); 1399 s(CH3); 1351 (SO2); 1183 (C-O); 1135 (S=O); 1055 (S=O); 947 (C-H);
788 (CH2); 742 s (CF3); 654 (SNS); 616 a(SO2); Elemental analysis calcd (%) for C20H36F6N2O6S2:
ν
ν
ν
ν
ν
δ
δ
ν
ν
ν
ν
δ
δ
δ
δ
δ
C, 41.52; H, 6.27; N, 4.84. Found (%): C, 41.64; H, 6.05; N, 4.78.
N-[2-(Acryloyloxy)ethyl]-N,N,N-triethylammonium bis(trifluoromethanesulfonyl)imide
([C2NA,22]TFSI)
The IL was prepared accordingly to the procedure described above for [C2NMA,22]TFSI starting
from [C2NA,22]I (24.451 g, 75.0 mmol) in water (15 mL) and LiTFSI (22.501 g, 68.38 mmol) in water
(15 mL). The product was received as colorless oil (30.64 g, 85.0% yield). 1H NMR (500 MHz,
acetone-D6):
6.00 (dd, 1H, CH2); 6.22 (m, 1H, CH); 6.42 (dd, 1H, CH2); 13C NMR (125 MHz, acetone-D6):
6.9 (CH3); 53.7 (CH2); 55.1 (CH2); 57.3 (CH2); 120.1 (q, CF3); 127.6 (CH); 131.7 (CH2); 164.8 (C=O);
IR (cm−1): 2996
(C-H); 1730 (C=O); 1638 (C=C); 1461 as(CH2); 1410 s(CH3); 1349 (SO2); 1177
(C-O); 1135 (S=O); 1053 (S=O); 996 (CH2); 788 (CH2); 742 (CF3); 654 (SNS); 614 a(SO2);
δ
(ppm) 1.44 (t, 9H, CH3); 3.62 (q, 6H, CH2); 3.83 (m, 2H, CH2); 4.67 (s, 2H, CH2);
δ
(ppm)
ν
ν
ν
δ
δ
ν
ν
ν
ν
δ
δ
δ
s
δ
δ
Elemental analysis calcd (%) for C13H22F6N2O6S2: C, 32.50; H, 4.62; N, 5.83. Found (%): C, 32.45; H,
4.40; N, 5.83.
N-[2-(Acryloyloxy)ethyl]-N-butyl-N,N-diethylammonium bis(trifluoromethanesulfonyl)imide
([C4NA,22]TFSI)
The IL was prepared accordingly to the procedure described above for [C2NMA,22]TFSI starting
from [C4NA,22]I (26.645 g, 75.0 mmol) in water (20 mL) and LiTFSI (22.501 g, 68.38 mmol) in water
(15 mL). The product was received as colorless oil (30.49 g, 80.5% yield). 1H NMR (500 MHz,
acetone-D6):
3.62 (s, 4H, CH2); 3.84 (s, 2H, CH2); 4.67 (s, 2H, CH2); 6.00 (m, 1H, CH2); 6.21 (m, 1H, CH); 6.42 (m,
1H, CH2); 13C NMR (125 MHz, acetone-D6):
(ppm) 7.0 (CH3); 12.9 (CH2); 19.4 (CH2); 23.4 (CH2);
δ (ppm) 1.00 (s, 3H, CH3); 1.43 (s, 8H, CH3, CH2); 1.83 (s, 2H, CH2); 3.48 (s, 2H, CH2);
δ

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54.2 (CH2); 55.7 (CH2); 57.3 (CH2); 58.1 (CH2); 120.1 (q, CF3); 127.6 (CH); 131.7 (CH2); 164.8 (C=O);
IR (cm−1): 2961
(C-H); 2935 (C-H); 2866 (C-H); 1730 (C=O); 1638 (C=C); 1463 as(CH2); 1408
s(CH3); 1351 (SO2); 1179 (C-O); 1135 (S=O); 1055 (S=O); 790 (CH2); 742 (CF ); 654 (SNS);
616 a(SO2); Elemental analysis calcd (%) for C15H26F6N2O6S2: C, 35.43; H, 5.15; N, 5.51. Found (%):
ν
ν
ν
ν
ν
δ
δ
ν
ν
ν
ν
δ
δ
δ
s
3
δ
C, 35.45; H, 5.15; N, 5.57.
N-[2-(Acryloyloxy)ethyl]-N,N-diethyl-N-hexylammonium bis(trifluoromethanesulfonyl)imide
([C6NA,22]TFSI)
The IL was prepared accordingly to the procedure described above for [C6NMA,22]TFSI starting
from [C6NA,22]I (24.915 g, 65.0 mmol) in acetone (40 mL) and LiTFSI (19.501 g, 67.9 mmol) in water
1
(30 mL). The product was received as colorless oil (31.20 g, 89.5% yield). H NMR (500 MHz, CDCl3):
δ
(ppm) 0.89 (s, 3H, CH3); 1.33 (s, 12H, CH3, CH2); 1.66 (s, 2H, CH2); 3.21 (m, 2H, CH2); 3.38 (m, 4H,
CH2); 3.60 (s, 2H, CH2); 4.52 (s, 2H, CH2); 5.96 (m, 1H, CH2); 6.11 (m, 1H, CH); 6.44 (m, 1H, CH2);
13C NMR (125 MHz, CDCl3):
(ppm) 7.4 (CH3); 13.7 (CH2); 21.7 (CH2); 22.3 (CH2); 25.8 (CH2); 31.0
(CH2); 54.5 (CH2); 55.8 (CH2); 56.9 (CH2); 58.7 (CH2); 119.8 (q, CF3); 126.9 (CH); 132.8 (CH2); 165.1
(C=O); IR (cm−1): 2972
(C-H); 2883 (C-H); 1732 (C=O); 1637 (C=C); 1463 as(CH2); 1408 s(CH3);
1349 (SO2); 1179 (C-O); 1135 (S=O); 1053 (S=O); 790 (CH2); 740 (CF ); 653 (SNS); 614 a(SO2);
δ
ν
ν
ν
ν
δ
δ
ν
ν
ν
ν
δ
δ
s
δ
δ
3
Elemental analysis calcd (%) for C17H30F6N2O6S2: C, 38.06; H, 5.64; N, 5.22. Found (%): C, 37.70; H,
5.63; N, 5.13.
N-[2-(Acryloyloxy)ethyl]-N,N-diethyl-N-octylammonium bis(trifluoromethanesulfonyl)imide
([C8NA,22]TFSI)
The IL was prepared accordingly to the procedure described above for [C6NMA,22]TFSI starting
from [C8NA,22]I (26.739 g, 65.0 mmol) in acetone (40 mL) and LiTFSI (19.501 g, 67.9 mmol) in water
1
(30 mL). The product was received as colorless oil (32.77 g, 89.3% yield). H NMR (500 MHz, CDCl3):
δ
(ppm) 0.88 (t, 3H, CH3); 1.28 (m, 6H, CH2); 1.34 (t, 10H, CH3, CH2); 1.66 (s, 2H, CH2); 3.20 (m, 2H,
CH2); 3.39 (q, 4H, CH2); 3.60 (m, 2H, CH2); 4.52 (m, 2H, CH2); 5.96 (dd, 1H, CH2); 6.12 (m, 1H, CH);
6.45 (dd, 1H, CH2); 13C NMR (125 MHz, CDCl3):
(ppm) 7.4 (CH3); 14.0 (CH2); 21.8 (CH2); 22.5 (CH2);
26.1 (CH2); 28.9 (CH2); 31.5 (CH2); 54.5 (CH2); 55.8 (CH2); 56.9 (CH2); 58.7 (CH2); 119.8 (q, CF3); 126.9
(CH); 132.9 (CH2); 165.1 (C=O); IR (cm−1): 2959
(C-H); 2932 (C-H); 2860 (C-H); 1732 (C=O); 1638
(C=C); 1465 as(CH2); 1408 s(CH3); 1349 (SO2); 1179 (C-O); 1135 (S=O); 1055 (S=O); 790 (CH2);
742 s (CF3); 656 (SNS); 616 a(SO2); Elemental analysis calcd (%) for C19H34F6N2O6S2: C, 40.42; H,
6.07; N, 4.96. Found (%): C, 41.04; H, 6.01; N, 5.06.
δ
ν
ν
ν
ν
ν
δ
δ
ν
ν
ν
ν
δ
δ
δ
δ
Author Contributions: Conceptualization, A.H. and T.H.; Funding acquisition, A.H.; Investigation, R.L.;
Methodology, R.L. and A.H.; Project administration, A.H. and T.H.; Resources, T.H.; Supervision, A.H. and
T.H.; Visualization, R.L.; Writing—original draft, R.L.; Writing—review & editing, R.L., T.H. and A.H.
Funding: This research was founded by the Deutsche Forschungsgemeinschaft (Sachbeihilfe, HO 5266/1-2).
Acknowledgments: We acknowledge support by Deutsche Forschungsgemeinschaft and Open Access Publishing
Fund of Karlsruhe Institute of Technology.
Conflicts of Interest: The authors declare no conflict of interest.
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Sample Availability: Samples of the compounds are not available from the authors.
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