The local composition behavior in binary solutions of diethylamine acetate ionic liquid

Article abstract of DOI:10.1016/j.molliq.2015.11.008

In order to uncover the micro-structural heterogeneities in the solutions of ammonium-based ionic liquids, diethylamine acetate (DEAA) has been synthesized and concentration-dependent ¹H NMR spectra of three binary solutions, namely DEAA/water,

Full text of DOI:10.1016/j.molliq.2015.11.008

Journal of Molecular Liquids 213 (2016) 139–144
Contents lists available at ScienceDirect
Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
The local composition behavior in binary solutions of diethylamine
acetate ionic liquid
a,
a
b
Xiao Zhu ⁎, Huan Zhang , Yingjie Xu
a
School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, China
Department of Chemistry, Shaoxing University, Shaoxing 312000, China
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 17 July 2015
Received in revised form 2 November 2015
Accepted 3 November 2015
Available online 6 December 2015
In order to uncover the micro-structural heterogeneities in the solutions of ammonium-based ionic liquids,
diethylamine acetate (DEAA) has been synthesized and concentration-dependent H NMR spectra of three bina-
1
ry solutions, namely DEAA/water, DEAA/DMSO and DEAA/acetone, at different compositions have been mea-
1
sured at 298.15 K. The proton chemical shifts of DEAA have been correlated using the H NMR local
composition (LC) model. It has been found that the self-associations of DEAA were predominant instead of
DEAA–solvent interactions within DEAA-rich region. However within solvent-rich region, DEAA could mainly in-
teract with solvent molecules, indicating that the network of DEAA has been greatly destroyed by effects of sol-
vents. In addition, the ability of solvents to break down the structure of DEAA followed in such order:
water N DMSO N acetone, which was consistent with changes of physicochemical properties of these solutions.
© 2015 Elsevier B.V. All rights reserved.
Keywords:
1
H NMR chemical shifts
Local composition model
Density
Viscosity
Electric conductivity
1
. Introduction
methods have clearly illuminated that nano-inhomogeneity could be
generated in aqueous solutions of ILs. The study [15] on the DMSO/
Ammonium-based ionic liquids (ILs) are a kind of typical protic ILs
PILs), which have similar properties like other ILs such as wide liquid
2 2
[N(4)111] [Tf N] and DMSO/[bmim] [Tf N] have shown that DMSO in
mixtures with ILs could tend to produce clusters, instead of homoge-
neous mixing. Moreover the formation of localized, self-segregated,
(
range, good solubility with other solvents, and property-adjustable ac-
cording to different combinations of cations and anions. Furthermore
they also have many special characteristic, like low cost, high conductiv-
ity and easy to prepare through direct neutralization reaction, which
endow them excellent performance in catalyst for organic reactions
6
hydrogen-bonded nanostructures within the [bmim][PF ]/TEG binary
mixture has also been revealed [16]. Accordingly it has been empha-
sized that [17] considerable efforts are expected to be applied to
the investigation of structural heterogeneities in mixtures of ILs, in par-
ticularly with molecular solvents.
[
2 2
1], absorption of H S [2] and CO [3], U(VI) extraction [4], stability of
proteins [5], dissolution of chitosan [6], electrochemistry [7] and waste-
water treatments [8]. It is easy to understand that the knowledge of the
ammonium-based ILs with molecular solvents is essential for their ap-
plications in chemical and industry processes. Some physiochemical
properties of solutions, such as viscosity, density and conductivity,
have been measured and the interactions between ILs and solvents
have also been discussed [9–10]. The physicochemical properties of ILs
could be considerably affected by the molecular solvents, which can re-
veal that the micro-structure of solutions could be characteristically
changed since the properties depended on the structures. Recently the
local composition phenomenon in some solutions of ILs has been ob-
served, indicating that the ILs may not mix homogeneously with the
molecular solvents. Theoretical [11–12] and experimental [13–14]
Recently NMR has been frequently utilized to study the in-
homogeneous in the mixtures of ILs due to its accuracy and sensitivity
[18–19]. Undoubtedly the H NMR chemical shifts can help us to deter-
1
mine the number and category of protons in pure substance. Moreover,
1
H NMR chemical shifts could also offer us much information conve-
niently about microscopic structure within solutions, since the chemical
environments of protons could be changed due to the intermolecular
interactions. More interestingly, 1H NMR chemical shifts could be
analyzed quantitatively by certain theoretical models. In our previous
work [20], 1H NMR chemical shifts of aqueous solutions of n-
3
butylammonium nitrate (N4NO ) ionic liquid has been successfully cor-
1
related using the H NMR local composition (LC) mode. Based on this,
the local mole fractions of ILs and solvents could be calculated, which
could indicate the structural heterogeneities in mixtures of ILs. There-
fore in order to obtain more information about ammonium-based ILs,
the diethylammonium acetate (DEAA) ionic liquid has been investigat-
ed in the present paper. Although DEAA has been reported as the
⁎
Corresponding author.
E-mail address: xiaoxiao1982820@163.com (X. Zhu).
http://dx.doi.org/10.1016/j.molliq.2015.11.008
167-7322/© 2015 Elsevier B.V. All rights reserved.
0

140
X. Zhu et al. / Journal of Molecular Liquids 213 (2016) 139–144
stabilizers for the structure of amino acids [21] and its thermophysical
properties with DMF have been measured [22], the micro-structure of
mixtures of DEAA remains obscure. The selective molecular solvents
herein are water, DMSO and acetone. It is well known that hydrophile
is the representative properties of IL family, which could result in the
distinct changes of IL properties. DMSO is famous for its special dissolv-
ing capacity and high polarity, which is, often in company with ionic liq-
uids, used to promote chemical reactions [23–24] and biological
processes [25]. Acetone, as another common organic solvent, has been
regarded as almost universal solvent for ILs and several properties for
the acetone–IL system have been achieved [26]. Consequently our tar-
get herein is to obtain the information about the microscopic local struc-
tures of DEAA/water, DEAA/DMSO and DEAA/acetone solutions using
1
H NMR coupled with LC model, which is interesting and necessary
for their applications.
2
2
2
. Experiments and theory
Fig. 1. Experimental and correlated 1H NMR chemical shifts of –CH
water system at 298 K: ●: experimental values; —: correlated values.
3
of DEAA in DEAA/
.1. Experiments
.1.1. Synthesis of DEAA ionic liquid
DEAA was prepared from diethylamine and acetate acid according to
2.1.3. Measurements of viscosity, density and electrical conductivity
The viscosity was determined by an Ubbelohde viscometer (inner
diameter = 1.5 mm), which was put in the water bath at 25 ± 0.1 °C.
The measurements were carried out three times for each sample. In
order to avoid the moisture absorption, the ionic liquid was dried in a
vacuum oven at 70 °C for 24 h before use. And experimental data have
been illustrated in Fig. 4.
the procedure reported previously [27] (see Scheme 1). Acetate acid
CAS No. 64-19-7), diethylamine (CAS No. 109-89-7), DMSO (CAS No.
7-68-5) and acetone (CAS No. 67-64-1) were analytical grade, which
(
6
were purchase from Tianjin Damao Chemical Reagent Factory (Tianjin,
China). Specific synthesis processes of DEAA were as follows: into a
1
00 mL three-necked flask under magnetic stirring, 0.55 mol of
The electrical conductivities of all solutions were measured with an
electrical conductivity meter produced by Shanghai Precision & Scientif-
ic Instrument Co., Ltd. (DDS-11D). The cell constant was determined by
diethylamine was placed, and then 0.50 mol of acetate acid was
dropped in slowly. After the neutralization reaction for 6 h at 40 °C
water-bath, the sample was purified using the rotary evaporation at
−
1
0.1 mol∙L
aqueous solution of KCl at 298.15 K. Because of the ex-
7
0 °C. Then viscous and clear liquid DEAA was obtained, which was
tremely large electric conductivity of DEAA/water system, the cell con-
stant of electrode that has been used to explore the κ of aqueous
solutions is about 10.95 (DJS-10) in order to enlarge the measuring
range. Each sample was placed in water bath which was controlled to
25 ± 0.1 °C for 30 min before measurement. Each conductivity value
of the samples was reported by averaging three consecutive runs and
experimental data have been illustrated in Fig. 5.
then dried under vacuum at 70 °C for at least 48 h before use. The
water content was determined below 200 ppm analyzed by Karl–Fi-
scher titration. The structure of DEAA was identified by H NMR spectra
1
1
(
(
Bruker). The chemical shifts δ (ppm) were as follows: H NMR
400 MHz, CHCl ), 2.9(4 H, −CH
+
3
-d), δ (ppm): 9.9(2 H, NH
2
2
),
−
1
.9(3 H, −CH -COO ), 1.3(6 H, −CH ), which was corresponding
3
3
well to the protons of DEAA. All of solutions of ILs were prepared by
weight using an analytical balance with a precision of ± 0.0001 g over
the whole concentration range. Deionized double-distilled water has
been used to make aqueous solutions of DEAA.
The density of solutions was measured using pycnometer method.
Each sample was placed in water bath which was controlled to 25 ±
0.1 °C for 30 min before measurement. Each density value of the sam-
ples was obtained by averaging three consecutive runs. And experimen-
tal data have been illustrated in Fig. 6. In addition, the physiochemical
1
2
.1.2. Measurement of H NMR chemical shifts of solutions at different
concentrations
The internal reference method [28] was adopted to obtain the
concentration-dependent chemical shifts of certain group in DEAA. To
avoid the influence of deuterated reagents, a 2-mm capillary tube, in
which the deuterated chloroform (CHCl
the center of a 5-mm sample tube filled with the chemical shift refer-
ence of tetramethylsilane (TMS) or (CH Si(CH SO Na (DSS, used
3
-d) was sealed, was placed at
3
)
3
2
)
3
3
in aqueous solutions of DEAA) and the sample solutions. It is demanded
that the inner capillary tube should be kept parallel with the exterior
1
sample tube. The H NMR spectra were obtained using a Bruker AV
4
2
00 spectrometer operating at 400 MHz at different concentrations at
98.15 K and all of the experimental data were included in Figs. 1–3.
Fig. 2. Experimental and correlated 1H NMR chemical shifts of –NH of DEAA in DEAA/
DMSO system at 298 K: ●: experimental values; —: correlated values.
Scheme 1. Molecular structure and synthesis of DEAA ionic liquid.

X. Zhu et al. / Journal of Molecular Liquids 213 (2016) 139–144
141
Fig. 3. Experimental and correlated 1H NMR chemical shifts of –CH
Fig. 5. Conductivity κ vs mole fraction of DEAA for binary solutions at 298.15 K.
2
of DEAA in DEAA/ac-
etone system at 298 K: ●: experimental values; —: correlated values.
Λ21x2
¼
properties of pure components have been measured and concluded in
Table 1.
φ21
ð3Þ
ð4Þ
x1 þ Λ21x2
V2
2
.2. Theory
Λ21 ¼
exp½−ðg21−g11Þ=RTꢀ
V1
In 1964, Wilson first [29] proposed the local composition concept to
where g21 and g11 are proportional to the 1–2 and 1–1 interaction ener-
gies, respectively, where V and V are the mole volumes of DEAA and
describe the microscopic solution structure, which has been extensively
applied to correlate vapor–liquid equilibrium data of binary and multi-
component mixtures. Based on the Wilson's assumption, we believed
1
2
solvent which are calculated by division of molecular weight and
density (the measured density of DEAA, DMSO and acetone at
1
that the observed H NMR chemical shifts of DEAA in solutions could
−
3
−3
−3
2
98.15 K are 1.0214 g∙cm , 1.1088 g∙cm
and 0.7880 g∙cm
re-
be simply expressed as follows:
spectively using the pycnometer method). x
1
and x denote bulk mole
2
fractions of DEAA and solvent, respectively. The following objective
function is used,
0
1
∞
1
δ1;cal ¼ δ φ þ δ φ
ð1Þ
11
21
"
#1=2
m
X
where 1 and 2 denote DEAA and solvent separately. φ11 and φ21 are
1
2
OF ¼
ðδ1;cal;k−δ1; exp;k
Þ
ð5Þ
local volume fractions of DEAA and solvent around DEAA, respectively.
m−1
k¼1
0
∞
δ
1
and δ
1
are pure substance and infinitely dilute chemical shifts of a
∞
certain proton of DEAA, respectively. δ
1
is usually obtained by extrapo-
where m denotes the size of the experimental data set. δ1,cal,k denotes
kth calculated chemical shifts according to Eq. (1). δ1,expl,k denotes the
kth experimental value, and (g21–g11) is the only optimized parameter.
According to Eqs. (1)–(4), the chemical shifts of DEAA in binary
lating the dilute chemical shift to zero concentration. Then the local
molar volume fractions can be defined as follows:
x1
φ11
¼
ð2Þ
x1 þ Λ21x2
Fig. 4. Viscosity η vs mole fraction of DEAA for binary solutions at 298.15 K.
Fig. 6. Density ρ vs mole fraction of DEAA for binary solutions at 298.15 K.

142
X. Zhu et al. / Journal of Molecular Liquids 213 (2016) 139–144
Table 1
correlated with the only optimized parameter (g21–g11). Clearly as
shown in Figs. 1–3, the chemical shifts of DEAA in solutions could be
well correlated by this semi-empirical LC model.
Viscosities η and density ρ of the pure solvent at 298.15 K.
ρ/g∙cm−
3
Solvent
η/mPa∙s
This work
Lit.
This work
Lit.
Water
Acetone
DMSO
0.894
0.309
2.015
0.891 [27]
0.306 [34]
2.012 [40]
0.998
0.789
1.095
0.9971 [27]
0.784 [34]
1.095 [34]
3.2. Local composition in the binary solutions
According to local composition theory, the binary solutions of ILs
should not be completely homogeneous in the local area. Therefore in
the vicinity of any component, the number of ionic liquid or molecular
solvent in the local area should be not always the same as in the bulk,
which is so-called the local composition. Actually such local composi-
tion behavior has been detected in 1-ethyl-3-methylimidazolium
mixtures can be correlated using one set of energy parameter and the
root-mean square deviations are defined as follows,
"
ꢂꢀ
ꢁꢃ2
#
1
=
m
2
tetrafluoroborate (EmimBF )/water and n-butylammonium nitrate
4
X
1
m
δ1;cal;k−δ1; exp;k
1
Δδ% ¼
ꢁ 100%
ð6Þ
ð7Þ
(N NO )/water systems using H NMR chemical shifts and LC model
4
3
δ1; exp;k
k¼1
[31]. In DEAA/DMSO system, for example, since DEAA is considered as
the substance 1, x11 denotes the local mole fractions of DEAA around
the DEAA. And x21 denotes the local mole fractions of DMSO around
the DEAA. With the help of the LC model, the local mole fractions x11
"
#
1
2
=
2
m
Xꢀ
ꢁ
1
m
Δδ ¼
δ1;cal;k−δ1; exp;k
:
k¼1
and
Eqs. (8)–(9) since the (g21–g11) can be obtained by the correlation of
δ(−NH ) in DEAA. In order to illustrate the local composition more
x21 at different compositions could be calculated using
The (g21–g11) and correlated deviations of two systems were listed
in Table 2. According to Wilson's definition of local composition (LC)
for a binary mixture, we believed that the ratios of the probability of
finding the molecule 2 around the central molecule 1 should be defined
as follows,
2
clearly, the concentration-dependent (x11–x21) of three systems has
been shown graphically in Fig. 7. The (x11–x21), which denotes the dif-
ference between the local mole fraction of DEAA and solvent in the vi-
cinity of DEAA, behaves similar trend within three systems and
decreasing from 1 to −1 with x
over the whole concentration range. Apparently there are only DEAA
in the pure ionic liquid, when x11 = 1, x = 0 and x21 = 0. With the con-
2
(the bulk mole fraction of solvent)
x21
x11
x2 expð−g =RTÞ x2
2
1
¼
¼
exp½−ðg21−g11Þ=RTꢀ
ð8Þ
x1 expð−g =RTÞ x1
11
2
centration of solvent increasing, (x11–x21) becomes smaller and the
amount of solvent gathering around DEAA keeps increasing, indicating
solvent molecules could gradually get into the original self-associated
where x11 and x21 denote the local mole fraction of DEAA and solvent
around DEAA respectively. Apparently the local mole fractions of
DEAA and solvent should be unity. Thus,
organization of DEAA. Clearly when x(DMSO) b 0.4, the value of (x11
21) keeps positive, indicated that there are more DEAA but fewer
DMSO distributed around DEAA. However within the DMSO-rich region
when x(DMSO) N 0.4), the values of (x11–x21) exhibit negative, indicat-
–
x
x11 þ x21 ¼ 1:
ð9Þ
(
Subsequently the value of x11 and x21 can be obtained and then the
concentration-dependent (x11–x21) and (x –x11) could be calculated.
ing the predomination of the interactions between DEAA and DMSO in-
stead of self-association of DEAA. Accordingly the (x11–x21) could offer
us a picture of the change of micro-structure of binary solutions. Within
DEAA-rich region, the self-associations among DEAA should preferably
dominate in the DEAA/DMSO solutions. With the concentration of
DMSO increasing, much more DMSO could located around DEAA and
the original network of DEAA could be gradually broken down due to
the interactions between the solvent and DEAA. In the DEAA/water
and DEAA/acetone system, the local structure of solutions has
shown similar variation. It has been reported [15] that DMSO
1
3
. Results and discussion
1
3
.1. Correlation of H NMR chemical shifts
Recently the nature of the species contained in PILs has been
discussed warmly. The common knowledge have displayed that the
neutral molecules could form in pure PILs due to the proton-transfer
from Brøsted acids to the Brøsted bases. Actually it has been verified
[
30] that no acetic acid molecule has been detected in DEAA liquid
through the ATR-FTIR spectral analysis. And it has been reported that
the ionicity of DEAA decreased with an increase of temperature. Conse-
quently it is reasonable to believe that ions pairs rather than neutral
molecules could play dominant role in DEAA at 298.15 K. Based on
1
those results, the correlation of H NMR chemical shifts of DEAA in solu-
tions using LC model has been performed. Taking DEAA/DMSO for ex-
ample, the DEAA could simply be regarded as the entirety which was
designated as central substance 1 and DMSO is assigned to 2. Thus, ac-
cording to Eqs. (1)–(4) the chemical shifts of –NH (whose chemical
2
shifts change most obviously with concentrations) in DEAA can be
Table 2
The energy parameter (g21–g11) and the deviations of correlation of 1H NMR chemical
shifts.
21–g11)/J∙mol−
1
Δδ/ppm
Δδ %
(
g
DEAA/water
DEAA/DMSO
DEAA/acetone
−3111.8
3345.9
56.5
0.0043
0.0757
0.0048
0.29%
0.78%
0.14%
Fig. 7. Concentration-dependent (x11–x21) for binary solutions of DEAA.

X. Zhu et al. / Journal of Molecular Liquids 213 (2016) 139–144
143
E
could not completely mixed with ionic liquid in DMSO/
trimethyl(butyl)ammonium bis((trifluoromethyl)sulfonyl)imide
N(4)111][Tf N] mixtures. P. Venkatesu et al. [32–33] have studied the
mixtures of trimethylammonium-based ILs/DMSO and detected that
DMSO molecules could reduce hydrogen bonding between the cation
and anion due to ion–dipole interactions between DMSO and ILs. How-
ever at higher IL concentration, the interactions between DMSO and IL
became weaker and extensive self-association in the IL has been detect-
ed. Our findings here could further support such viewpoints.
Furthermore, the excess molar volumes (V ) are calculated by Eq.
(10):
[
2
ꢄ
ꢅ
x1M1 þ x2M2
x1M1 x2M2
VE
¼
−
þ
ð10Þ
ρ
ρ1
ρ2
where ρ are the density of solutions, and x and M represent the mole
fractions and molar masses, respectively. Subscripts 1 and 2 correspond
to pure DEAA and solvents, respectively. All values of excess molar vol-
ume have been calculated and shown in Fig. 9. Although all of V values
were negative, the absolute values of V in DEAA/water system behave
E
In addition, it is interesting to focus on the differences of three
E
systems. As shown in Fig. 7 when x(water) N 0.2, the value of (x11
–
E
x
21) b 0, indicating there are more water but fewer DEAA distributed
largest among all systems. Since V can express the nonideality of mix-
around DEAA within such concentration range. However in the case of
DEAA/acetone, the interactions between acetone and DEAA could not
predominate before x(acetone) reaches 0.5. In other words, water mol-
ecules could be more ready to break into the self-association structure
of DEAA compared to acetone and DMSO. Generally the viscosity and
electric conductivity of mixtures changing with concentrations could
reflect the influence of solvents. Firstly as shown in Fig. 4, the viscosity
η of all solutions decreased greatly with solvents increasing. However
the slope of curve corresponding to DEAA/water system was more neg-
ative than DEAA/DMSO and DEAA/acetone system, especially within the
range 0 b x(DEAA) b 0.7, indicating that water could reduce the viscosity
of DEAA more drastically compared to DMSO and acetone. In the case of
electric conductivity κ shown in Fig. 5, with mole fraction of DEAA in-
creasing, κ sharply increased in solvent-rich region and then progres-
sively became smaller in DEAA-rich region. And the maximal value of
κ of DEAA/water appears much larger than other two systems, indicat-
ing water molecules should be more effective to promote the dissocia-
tion of DEAA. Accordingly the experimental data of viscosity and
electric conductivity could demonstrate that water molecules could be
easy to interact with DEAA ionic liquid, which obviously was coherent
with local composition analysis.
tures, it can be deduced that the aqueous solutions of DEAA behave the
most significant local heterogeneities, which was consistent with LC
results.
Subsequently according to the local composition model coupled
with physicochemical properties of solutions, it could be demonstrated
that the ability of solvents to breakdown the network of DEAA should be
in such order: water N DMSO N acetone, which is well consistent with
the order of their dielectric constants. Actually it has been reported
that the effect of the molecular solvents on the network of ILs mainly
depended on the solvent dielectric constant [35]. And the solvents
with higher dielectric constant show better miscibility with ILs while
nonpolar solvents demonstrate poorer miscibility, indicating that
polar solvents have stronger molecular interaction with ILs [36–37].
Moreover other studies [35,38] have pointed out that molecular sol-
vents with high dielectric constant are more impactful in disruption of
the electrostatic attraction between the ions of the ILs. Accordingly the
dielectric constant of the molecular solvents should play the major
role in determining the structure and properties of IL in solutions. In ad-
dition to the highest dielectric constant of water, the strong hydrogen
bonding between DEAA and water molecules [39] also give rise to the
conspicuous changes of structure and properties of DEAA/water system.
Besides the difference between the local and bulk composition (x
11) has been calculated from local composition model and shown in
Fig. 8. Since x and x11 denote the bulk and local concentrations of
DEAA respectively, the absolute values of (x –x11) represent the extent
of local composition in the binary solutions. It can be evidently detected
that the absolute values of (x –x11) is largest in DEAA/water system and
smallest in DEAA/acetone system, indicating that structural heterogene-
ities should be most remarkable in aqueous solutions of DEAA and be
weakest in DEAA/acetone system. In order to elucidate this, the density
ρ of three systems have been measured and illustrated in Fig. 6. Evident-
ly ρ of DEAA/DMSO and DEAA/water systems gradually decreased and ρ
of DEAA/acetone increased with DEAA increasing, which are quite in
agreement with the results of [Bmim]Cl system [34].
1
–
x
4. Conclusions
1
With the help of LC model, the correlations of 1H NMR chemical
shifts of three systems, DEAA/water, DEAA/DMSO and DEAA/acetone,
have been performed. The local mole fractions have revealed that sol-
vents could not mix homogeneously with DEAA in the local area. Fur-
thermore the micro-structure of systems could change with the
concentration of solutions. Specifically DEAA mainly self-associated
with each other in DEAA-rich region and a small quantity of solvents
could not induce great change of original network of DEAA. Neverthe-
less in solvent-rich region, DEAA could chiefly interact with molecule
solvents leaving fewer DEAA self-associated. In addition, compared to
1
1
E
1
Fig. 8. Concentration-dependent (x –x11) for binary solutions of DEAA.
Fig. 9. Excess molar volumes (V ) vs mole fraction of DEAA for binary solutions at 298.15 K.

144
X. Zhu et al. / Journal of Molecular Liquids 213 (2016) 139–144
[
[
10] U. Domanska, P. Papis, J. Szydlowski, M. Krolikowska, M. Krolikowski, J. Phys. Chem.
B 118 (2014) 12692–12705.
11] X.J. Zhong, Z. Fan, Z.P. Liu, D.P. Cao, J. Phys. Chem. B 116 (2012) 3249–3263.
DMSO and acetone, the water molecules appeared more ready to insert
into the network of DEAA. And the experimental data of density, viscos-
ity and electric conductivity have shown that water molecules display
more efficient to result in the dissociation of DEAA, which was consis-
tent with the effect of water on the micro-structure of DEAA. In one
word, the power of solvents to breakdown the self-associated network
of DEAA should be in such order: water N DMSO N acetone, which is in
accordance with their dielectric constants. Subsequently the molecular
solvents with higher dielectric constant should lead to more impact
on the structure and properties of DEAA ionic liquid.
Evidently it is considerable interesting and practical to study the
local heterogeneity of ILs in solutions which could dramatically affect
the properties of ILs/solvent systems. The present work offered us a
clear insight about the local structure variations in DEAA solutions in
the presence of solvents. More importantly it can provide a simple and
convenient avenue to study the microscopic structures of solutions of
ionic liquids, which exhibits agreement with other approaches.
[12] W. Jiang, Y. Wang, G.A. Voth, J. Phys. Chem. B 111 (2007) 4812–4818.
[
13] Y. Jeon, J. Sung, D. Kim, C. Seo, H. Cheong, Y. Ouchi, R. Ozawa, H. Hamaguchi, J. Phys.
Chem. B 112 (2008) 923–928.
14] S. Saha, H. Hamaguchi, J. Phys. Chem. B 110 (2006) 2777–2781.
[
[15] D.A. Ivanov, N.K. Petrov, O. Klimchuk, I. Billard, Chem. Phys. Lett. 551 (2012)
111–114.
[
[
16] A. Sarkar, S. Trivedi, G.A. Baker, S. Pandey, J. Phys. Chem. B 112 (2008) 14927–14936.
17] O. Russina, A. Triolo, L. Gontrani, R. Caminiti, J. Phys. Chem. Lett. 3 (2012) 27–33.
[18] Y. Xu, Y. Gao, L. Zhang, Y. Yao, C. Wang, H. Li, Sci. China: Chem. 53 (2010)
1561–1565.
[
[
[
19] Y. Zhao, S. Gao, J. Wang, J. Tang, J. Phys. Chem. B 112 (2008) 2031–2039.
20] X. Zhu, Y. Gao, L. Zhang, H. Li, J. Mol. Liq. 190 (2014) 174–177.
21] T. Vasantha, P. Attri, P. Venkatesu, R.S.R. Devi, J. Phys. Chem. B 116 (2012)
11968–11978.
[
22] P. Attri, P.M. Reddy, P. Venkatesu, A. Kumar, T. Hofman, J. Phys. Chem. B 114 (2010)
6126–6133.
[
23] S.N. Dighe, K.S. Jain, K.V. Srinivasan, Tetrahedron Lett. 50 (2009) 6139–6142.
[24] Y. Lee, K. Wu, Phys. Chem. Chem. Phys. 14 (2012) 13914–13917.
[
[
25] S. Deng, J. Cheng, X. Guo, L. Jiang, J.W. Zhang, J. Polym. Environ. 22 (2014) 17–26.
26] E. Ruiz, V.R. Ferro, J. Palomar, J. Ortega, J.J. Rodriguez, J. Phys. Chem. B 117 (2013)
7
388–7398.
Acknowledgments
[27] Y. Xu, J. Yao, C. Wang, H. Li, J. Chem. Eng. Data 57 (2012) 298–308.
28] R. Zhang, H. Li, Y. Lei, S. Han, J. Phys. Chem. B 109 (2005) 7482–7487.
29] G.M. Wilson, J. Am. Chem. Soc. 86 (1964) 127–130.
30] X. Sun, S. Liu, A. Khan, C. Zhao, C. Yan, T. Mu, New J. Chem. 38 (2014) 3449–3456.
[31] X. Zhu, Y. Wang, H. Li, AICHE J. 55 (2009) 198–205.
32] V. Govinda, P.M. Reddy, I. Bahadur, P. Attri, P. Venkatesu, P. Venkateswarlu,
[
[
[
This work was supported by the National Natural Science Founda-
tion of China (Nos. 21206085 and 21406140).
[
Thermochim. Acta 556 (2013) 75–88.
33] V. Govinda, P.M. Reddy, P. Attri, P. Venkatesu, P. Venkateswarlu, J. Chem.
Thermodyn. 58 (2013) 269–278.
34] H. Saba, X. Zhu, Y. Chen, Y. Zhang, Chin. J. Chem. Eng. 23 (2015) 804–811.
35] W. Li, Z. Zhang, B. Han, S. Hu, Y. Xie, G. Yang, J. Phys. Chem. B 111 (2007) 6452–6456.
36] P. Bonhote, A.P. Dias, N. Papageorgiou, K. Kalyanasundaram, M. Gratzel, Inorg. Chem.
References
[
[1] A. Taheri, X.J. Pan, C.H. Liu, Y.L. Gu, ChemSusChem 7 (2014) 2094–2098.
[2] K. Huang, X.M. Zhang, Y. Xu, Y.T. Wu, X.B. Hu, Y. Xu, AICHE J. 60 (2014) 4232–4240.
[3] M.E. Zakrzewska, A.A. Rosatella, S.P. Simeonov, C.A.M. Afonso, V. Najdanovic-Visak,
M.N. da Ponte, Fluid Phase Equilib. 354 (2013) 19–23.
[
[
[
35 (1996) 1168–1178.
[4] S. Biswas, V.H. Rupawate, S.B. Roy, M. Sahu, J. Radioanal. Nucl. Chem. 300 (2014)
[
[
37] L.A. Blanchard, J.F. Brennecke, Ind. Eng. Chem. Res. 40 (2001) 287–292.
38] J.N.C. Lopes, M.F.C. Gomes, P. Husson, A.A.H. Padua, L.P.N. Rebelo, S. Sarraute, M.
Tariq, J. Phys. Chem. B 115 (2011) 6088–6099.
39] R. Umapathi, P. Attri, P. Venkatesu, J. Phys. Chem. B 118 (2014) 5971–5982.
40] O. Ciocirlan, O. Iulian, J. Chem. Eng. Data 57 (2012) 3142–3148.
853–858.
[5] S. Bose, C.A. Barnes, J.W. Petrich, Biotechnol. Bioprocess Eng. 109 (2012) 434–443.
[6] X.F. Sun, Q.Q. Tian, Z.M. Xue, Y.W. Zhang, T.C. Mu, RSC Adv. 4 (2014) 30282–30291.
[7] M. Matsumiya, M. Ishii, R. Kazama, S. Kawakami, Electrochim. Acta 146 (2014)
[
[
371–377.
[
[
8] E. Grabinska-Sota, A. Dmuchowski, Przem. Chem. 87 (2008) 388–391.
9] M. Usula, E. Matteoli, F. Leonelli, F. Mocci, F.C. Marincola, L. Gontrani, S. Porcedda,
Fluid Phase Equilib. 383 (2014) 49–54.