Exploration of the soluting-out effect of carbohydrates on the micellization and surface activity of long-chain imidazolium ionic liquid in the aqueous medium

Article abstract of DOI:10.1016/j.molliq.2020.114209

In order to elucidate the role of polyhydroxy compounds (PHC) in modifying the micellization and interfacial behaviour of surface-active ionic liquids (SAILs), system consisting of 1-tetradecyl-3-methylimidazolium bromide ([C₁₄mim][Br]) in water and in aqueous solutions of D(+)-Xylose and D(+)-Glucose as additives at (298.15, 303.15 and 308.15) K using specific conductance, UV–visible spectroscopy, FT-IR spectroscopy, surface tension measurement was investigated. From the electrical conductivity measurements, various parameters such as critical micelle concentration (CMC), degree of ionization of the counterion on the micelles (α), the standard Gibbs energy of micellization (ΔG⁰_m), etc. have been evaluated for different concentrations of carbohydrates at different temperatures. FT-IR spectroscopy is utilized to record the structural changes occurring in the studied systems at below CMC, at CMC, and above CMC concentrations. The various surface parameters including CMC, surface tension at CMC (γ_cmc), surface pressure at the interface (?_cmc), the maximum surface excess concentration (Γ_max), and the minimum area per surfactant molecule at the surface, A_min have also been obtained using surface tension measurements. The results obtained indicated that the CMC value of the IL in the presence of different concentrations of carbohydrates decreases in the order; D(+)-Glucose > D(+)-Xylose demonstrating that carbohydrates have a soluting-out effect and their tendency to lower the CMC value of IL increases with an increase of hydrophilicity of carbohydrates.

Full text of DOI:10.1016/j.molliq.2020.114209

Journal of Molecular Liquids 319 (2020) 114209
Contents lists available at ScienceDirect
Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
Exploration of the soluting-out effect of carbohydrates on the
micellization and surface activity of long-chain imidazolium ionic liquid
in the aqueous medium
⁎
Harsh Kumar , Ramanjeet Kaur
Department of Chemistry, Dr B R Ambedkar National Institute of Technology, Jalandhar 144011, Punjab, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 7 July 2020
Received in revised form 20 August 2020
Accepted 1 September 2020
Available online 6 September 2020
In order to elucidate the role of polyhydroxy compounds (PHC) in modifying the micellization and interfacial be-
haviour of surface-active ionic liquids (SAILs), system consisting of 1-tetradecyl-3-methylimidazolium bromide
([C14mim][Br]) in water and in aqueous solutions of D(+)-Xylose and D(+)-Glucose as additives at (298.15,
303.15 and 308.15) K using specific conductance, UV–visible spectroscopy, FT-IR spectroscopy, surface tension
measurement was investigated. From the electrical conductivity measurements, various parameters such as crit-
ical micelle concentration (CMC), degree of ionization of the counterion on the micelles (α), the standard Gibbs
energy of micellization (ΔG0m), etc. have been evaluated for different concentrations of carbohydrates at different
temperatures. FT-IR spectroscopy is utilized to record the structural changes occurring in the studied systems at
below CMC, at CMC, and above CMC concentrations. The various surface parameters including CMC, surface ten-
sion at CMC (γcmc), surface pressure at the interface (ᴨcmc), the maximum surface excess concentration (Γmax),
and the minimum area per surfactant molecule at the surface, Amin have also been obtained using surface tension
measurements. The results obtained indicated that the CMC value of the IL in the presence of different concentra-
tions of carbohydrates decreases in the order; D(+)-Glucose > D(+)-Xylose demonstrating that carbohydrates
have a soluting-out effect and their tendency to lower the CMC value of IL increases with an increase of hydro-
philicity of carbohydrates.
Keywords:
1-tetradecyl-3-methylimidazolium bromide
D (+)-xylose
D (+)-glucose
FT-IR
UV–visible
CMC
Soluting-out
© 2020 Elsevier B.V. All rights reserved.
1. Introduction
assemble resulting in the formation of self-aggregate structures well
known as micelles is termed as critical micelle concentration (CMC).
The self-assembling mechanism of ionic liquids has become an at-
tractive area of research. The resulting micelles are then utilized as
media for a variety of chemical analysis and synthesis [1,2]. Ionic Liquids
(ILs) have developed as a new class of molten organic electrolytes
poised of an asymmetric organic cation, and inorganic anion, that are
not capable of forming organized crystal structure and thus exist in a liq-
uid state in the broad range of temperatures below 100 °C [3,4]. In
contrast to other molecular solvents, these ionic liquids incorporate
characteristic physical properties, including high thermal stability, neg-
ligible vapour pressure, non-flammability, electrically conducting, good
solvation ability for organic, inorganic and polymeric materials and
wide liquid range [5,6]. As a result of many such properties, ionic liquids
are found to have applications in diverse areas of chemistry, biological
engineering, chemical engineering, biochemistry where they facilitate
enzyme catalysed reactions [7], in protein-folding as co-solvents [8],
electrolytes in dye-sensitized solar cells [9]. The concentration of solu-
tion at which the ionic liquid surfactant molecules commences to self-
At the critical micelle concentration, the solutions of ionic liquid surfac-
tants display severe changes in the physico-chemical properties such as
conductivity, surface tension, UV–vis absorbance, turbidity, solute solu-
bility etc. [10].
Carbohydrates are organic compounds that are significant structural
constituents in living systems [11]. Due to their non-hazardous nature
and benign to mammalian tissues, they are broadly utilized in cosmetics
and pharmaceutical applications and also have nutritional value and in-
dustrial utilization [12,13]. Due to the flexible nature of carbohydrates
such as having the different number of carbon atoms as well as number
of –OH groups, varying in their point of attachment, open or closed ring
structure, presence of ketonic or aldehydic group accounts for the vari-
ety of interactions that exist between carbohydrate-surfactant systems.
The interactions between a hydrophobic and hydrophilic group in the
microenvironment of the surfactant compete eventually to influence
the aggregation phenomenon in aqueous solution.
Ionic Liquids in the presence of additives such as carbohydrates have
the capacity to amend the conformation of aqueous solutions of carbo-
hydrates that results in changing the outlook, stability, and rheology of
the solution [14–21]. The most frequently studied Ionic Liquids are the
⁎
Corresponding author.
E-mail address: manchandah@nitj.ac.in (H. Kumar).
https://doi.org/10.1016/j.molliq.2020.114209
0167-7322/© 2020 Elsevier B.V. All rights reserved.

H. Kumar and R. Kaur
Journal of Molecular Liquids 319 (2020) 114209
imidazolium-based Ionic Liquids; 1-Alkyl-3-methylimidazolium salts,
where cation is abbreviated as [Cn mim] +, n signifies the number of car-
bon atoms constituting the alkyl chain.
have been listed in Table 1 and their chemical structures have been pre-
sented in Scheme 1.
By adjusting the number of the carbon atoms on the alkyl chain
length, the cationic and anionic structure of the ILs, the micellization be-
haviour of ILs can be regulated [22–24]. When n > 8, they exhibit
surfactant-like behaviour and results in the formation of micellar aggre-
gates in the aqueous solution and are termed as Surface Active Ionic Liq-
uid [25–28]. Surface Active Ionic Liquids have been found to possess
advantages over conventional surfactants such as they possess lower
CMC values and also superior activity making the micellization process
an economical one.
Though a lot of work has been carried out to study the effect of dif-
ferent additives such as surfactants, drugs, amino acids, polyelectrolytes
etc. on the micellization behaviour of Ionic liquids using various tech-
niques [29–39], but very rare information for the effect of carbohydrates
as additive on the micellization behaviour of imidazolium-based ionic
liquids is available in the literature [40,41]. In this context, we investi-
gated the aqueous solution of the ionic liquid 1-tetradecyl-3-
methylimidazolium bromide ([C14mim][Br]) in the presence of carbo-
hydrates (D(+)-Xylose and D(+)-Glucose) at different concentrations
as well as different temperatures. The primary objective of the work is
to investigate the effects of carbohydrates (D(+)-Xylose, and D(+)-
Glucose) on the physicochemical characteristics, i.e. CMC, and various
parameters of thermodynamics of Ionic liquid through techniques
such as electrical conductivity, UV–Visible spectroscopy, and FT-IR and
surface tension measurements. In order to examine the interactions be-
tween ionic liquid and carbohydrates, measurements have been carried
out to determine the various thermodynamic parameters such as stan-
dard Gibbs free energy of micellization (ΔGm°), standard entropy of mi-
cellization (ΔSm°), standard enthalpy of micellization (ΔHm°) at (298.15,
303.15, 308.15) K.
2.2. Synthesis and characterization of ionic liquid 1-tetradecyl-3-
methylimidazolium bromide ([C14mim][Br])
The synthesis of the Ionic liquid 1-tetradecyl-3-methylimidazolium
bromide was carried out in the laboratory using the procedure de-
scribed in the literature [42]. The synthesis process was accomplished
through a direct reaction between 1-methylimidazole with an excess
amount of 1-bromotetradecane taken in a 500 ml round bottom flask,
both the chemicals dissolved using acetonitrile as the solvent. The reac-
tion mixture was then refluxed at a constant temperature of 78–80 °C
for almost 48 h. The ongoing reaction was continuously monitored
using thin-layer chromatography (TLC). After the success of the reac-
tion, two-phase mixture was obtained that consisted of a layer of ionic
liquid and acetonitrile that was expelled by decanting. [C14mimBr] syn-
thesis was terminated by washing the end product with ethyl acetate
and hexane at least three to four times and then the residual solvent
was removed by rota evaporator. The product was dried over vacuum
for 2 days before use. As a final point, the synthesized ionic liquid was
characterized by using the 1H NMR and FT-IR spectroscopy depicted in
Figs. S1 and S2 provided in the supplementary data.
2.3. Methods
The stock solutions of ionic liquid and carbohydrates were prepared
afresh by using the weighing Balance (Sartorius CPA 225 D having a pre-
cision of 0.00001 g). Freshly prepared deionized water doubly dis-
tilled over KMnO4 having specific conductance of <5 μS∙cm−1 has
been used throughout for all the measurements.
2.3.1. Conductivity measurements
2. Experimental
The conductivity measurements of ionic liquid 1-tetradecyl-3-
methylimidazolium bromide in water and in aqueous solutions of car-
bohydrates D(+)-Xylose and D(+)-Glucose having concentrations
(0.05, 0.25, 0.50) M was performed at different temperatures (298.15,
303.15, 308.15) K. Electrical conductivities of the prepared solutions
were determined using digital conductivity meter (Systronics 308) hav-
ing a dip type cell. The calibration of conductivity meter was accom-
plished taking the standard solution of KCl ([KCl] = 0.1000 M, κ =
12.97 mS·cm−1) [43]. For taking each measurement, freshly prepared,
double distilled deionized water having specific conductance of <5
μS∙cm−1 have been utilized for the preparation of solutions. The temper-
ature for the experiment was maintained constant by using a high
precision refrigerated circulated water thermostat procured from
Macro Scientific Works Pvt. Ltd., Delhi with the temperature range of
0–100 °C having an accuracy of 0.1 K. The sample solutions were
made homogeneous by making use of the magnetic stirrer. The solu-
tions were prepared in units of M (mole dm−3). After attainment of con-
stant temperature, the concentration of carbohydrates in solution was
varied by sequentially adding 200 μL aliquots of concentrated ionic
2.1. Chemicals
The synthesis of the ionic liquid 1-tetradecyl-3-methylimidazolium
bromide was carried out in the laboratory using 1-methylimidazole of
purity >99% which was procured from HIMEDIA Laboratories Pvt. Ltd.
and 1-bromotetradecane of purity >97% from Tokyo Chemical Industry
co., Ltd. Tokyo, Japan. Ethyl acetate with stated purity of >99% bought
from RFCL Limited India, Acetonitrile with purity >99.5% from LOBA
Chemie Pvt. Ltd. Mumbai has been also used for the synthesis. D(+)-Xy-
lose and D(+)-Glucose of purity >99% purchased from HIMEDIA Labo-
ratories Pvt. Ltd. was used without any further purification. All the
chemicals mentioned above as well as the synthesized ionic liquid
were dried under vacuum and stored over P2O5 in vacuum desiccator
for at least 48 h before their use. The solutions used in the experiment
were prepared in the doubly distilled deionized water. The details of
the chemicals used in this experiment i.e. the name of chemical, its
source, CAS No., purification method as well as mass fraction purity
Table 1
Specification of chemicals.
Chemicals
Source
CAS no
Purification method
Mass fraction puritya
1-methylimadazole
1-bromotetradecane
Ethyl acetate
Acetonitrile
D(+)-Xylose
D(+)-Glucose
1-Tetradecyl-3-methylimidazolium bromide
[C14mim][Br]
HIMEDIA Laboratories Pvt. Ltd
TCI Co. Ltd., Tokyo, Japan
RFCL Limited India
LOBA Chemie Pvt. Ltd. Mumbai
HIMEDIA Laboratories Pvt. Ltd
HIMEDIA Laboratories Pvt. Ltd
Synthesized in the laboratory
616-47-7
112-71-0
141-78-6
75-05-8
58-86-6
50-99-7
Used as such
Used as such
Used as such
Used as such
Used as such
Used as such
Vacuum drying
>99%
>97%
>99%
>99.5%
>99%
>99%
>99%b
471907-87-6
a
As declared by the supplier.
As per NMR analysis.
b
2

H. Kumar and R. Kaur
Journal of Molecular Liquids 319 (2020) 114209
Scheme 1. Chemical structures of investigated ionic liquid [C14mim][Br] and carbohydrates D(+)-Xylose and D(+)-Glucose.
liquid solution (having concentration 15–20 times the CMC) by means
of 10–100 μL micropipette. At least three readings were noted for each
concentration which resulted in reproducibility less than 0.5.
circulated water thermostat. The Wilhelmy plate was carefully cleaned
by firstly washing it with acetone and then dried by heating it red hot
on a flame to eradicate the adsorbed solutes before taking each mea-
surement. To calibrate the instrument as well to check the cleanliness
of glassware, the measurement for pure water at 298.15 K is carried
out. At least three readings were taken for each measurement and
then the average value is reported.
2.3.2. UV absorption spectra
For the estimation of the CMC of ionic liquid, probe less UV–Vis spec-
troscopy has been employed by which CMC is determined from the plot
of absorbance at fixed wavelength vs concentration of sample [44]. The
UV absorption spectra were recorded using Carry 631 UV–Vis spectro-
photometer (Agilent Technologies) by the use of quartz cuvette that
has a path length of 1 cm employed for the complete system involving
ionic liquid 1-tetradecyl-3-methylimidazolium bromide ([C14mim]
[Br]) in the absence and in the presence of aqueous solution of carbohy-
drates D(+)-Xylose and D(+)-Glucose at different concentrations i.e. at
0.05, 0.25 and 0.50 M at room temperature. The absorption spectra for
the whole system were recorded in the range of 200–800 nm. As can
be seen from the graphs obtained represented in Figs. 3 and 4, the con-
centration at the point of intersection of two straight lines in the plot of
absorbance versus concentration of [C14mim][Br] gives the value of CMC
3. Results and discussion
3.1. Micellization and interfacial studies
3.1.1. Conductivity measurements
The experimental electrical conductivity profiles of Ionic liquid
[C14mim][Br] in the absence and presence of different concentrations
of carbohydrates i.e. D(+)-Xylose and D(+)-Glucose (0, 0.05, 0.25
and 0.50 M) have been presented into Fig. 1 (in the absence and in
the presence of D(+)-Xylose) and Fig. 2 (in the presence of D(+)-Glu-
cose) at different temperatures i.e., 298.15 K, 303.15 K, 308.15 K. In the
plots for electrical conductivity versus concentration of ionic liquid in
the absence and presence of different carbohydrates, two distinguishing
straight lines referring to pre and post-micellar regions have been ob-
tained which are in agreement with the Onsager theory of electrolyte
and their x-intersection has been allocated the value of CMC. As can
be observed, with the increase in the concentration of ionic liquid, the
conductivity value is first increasing in the pre-micellar region due to
the increase in the number of free ions (C14mim+ and Br− ions). After
the breakpoint i.e. in the post-micellar region, the conductivity value
still increases however with the smaller slope for which the reason
lies in the fact that the micelles are less mobile in comparison to free
ions and also a significant loss of ionic charge occurs from the some of
the counter ions getting bind to the micellar surface. Tables 2 and 3
lists the values of conductivity measurements at different concentra-
tions and temperatures for the system studied. As can be seen from
the Tables, the specific conductivity values of the [C14mim][Br] ionic liq-
uid solution decreases more in the presence of D(+)-Glucose than D
(+)-Xylose which is in the same sequence as of their soluting-out
strength or even hydrophilicity of the respective carbohydrates. The ex-
planation for the fall in specific conductivity in the presence of carbohy-
drates is the reduction in the surface charge density of the head group of
IL [C14mim]+ on interaction with the hydroxyl groups of the carbohy-
drates. Such kind of interactions is increased by increasing the number
2.3.3. FT-IR spectroscopic studies
Fourier Transform –Infrared (FTIR) measurements were carried out
with the Shimadzu spectrometer 8400S and the accessible wavenumber
region for the FT-IR spectra recorded for the present work was in the
range 4000 cm−1 to 400 cm−1. The FT-IR spectra were recorded for
the three concentrations of carbohydrates (D(+)-Xylose and D(+)-
Glucose) i.e., 0.05, 0.25, 0.50 M in the aqueous solutions of Ionic liquid
at 298.15 K to gain insight about the interactions existing among the
ionic liquid and carbohydrates. For all the experimental procedures,
freshly made deionized doubly distilled (distilled using KMnO4) water
has been utilized.
2.3.4. Surface tension measurements
Surface tension measurements of the investigated aqueous solutions
of ionic liquid in the absence and in the presence of different carbohy-
drates have been carried out using Surface Tensiometer DCAT 15 pur-
chased from DataPhysics instruments, Germany having an accuracy of
0.01 mNm−1. Wilhelmy plate PT 11 and the dosing unit LDU 25 are
also provided along with the DCAT 33 software for the automated deter-
mination of CMC value. All the measurements were performed at
298.15 K, and the temperature was maintained using liquid tempera-
ture control unit TV 70 together with high precision refrigerated
3

H. Kumar and R. Kaur
Journal of Molecular Liquids 319 (2020) 114209
Fig. 1. Plots of specific conductance versus concentrations of ionic liquid [C14mim][Br] in water and D(+)-Xylose at different temperatures 298.15, 303.15 and 308.15 K and concentrations
0.05 M, 0.25 M, 0.50 M.
Fig. 2. Plots of specific conductance versus concentrations of ionic liquid [C14mim][Br] and D(+)-Glucose at different temperatures 298.15, 303.15 and 308.15 K and concentrations 0.05 M,
0.25 M, 0.50 M.
4

H. Kumar and R. Kaur
Journal of Molecular Liquids 319 (2020) 114209
Table 2
Conductivity values for [C14mim][Br]in the absence and in the presence of D(+)-Xylose at different molar concentrations and temperatures (T = 298.15 K, 303.15 K, and 308.15 K).
[C14mim] [Br]/mM
κ/μS cm−1
0 M D(+)-Xylose
T/K
0.05 M D(+)-Xylose
0.25 M D(+)-Xylose
0.50 M D(+)-Xylose
298.15
303.15
308.15
298.15
303.15
308.15
298.15
303.15
308.15
298.15
303.15
308.15
0.26316
0.51948
0.76923
1.01266
1.25000
1.48148
1.70732
1.92771
2.14286
2.35294
2.55814
2.75862
2.95455
3.14607
3.33333
3.51648
3.69565
3.87097
4.04255
4.21053
4.37500
4.53608
4.69388
4.84849
5.00000
5.14852
5.29412
26.72
44.20
54.40
74.00
92.37
110.4
127.8
145.0
161.5
177.1
192.8
207.2
214.2
218.5
223.7
228.8
231.6
236.9
241.0
243.8
248.3
253.5
255.8
259.0
262.2
264.8
265.9
29.30
50.55
67.82
84.17
104.9
126.1
142.6
162.7
181.9
202.1
219.8
235.1
245.1
251.3
256.0
261.4
265.3
270.7
275.2
278.9
282.5
286.5
291.4
296.3
299.9
303.7
306.9
37.20
57.45
81.19
101.5
119.4
141.0
158.8
174.7
194.9
212.4
231.5
249.9
265.9
277.6
286.5
292.8
298.8
303.5
307.6
312.5
317.8
320.4
325.8
329.6
331.8
336.6
338.9
25.34
42.10
57.70
72.78
87.40
101.7
114.7
129.8
143.4
156.3
169.9
176.7
182.6
186.7
189.6
193.5
196.9
200.3
203.7
206.7
209.9
212.8
215.6
218.6
221.3
224.0
226.7
33.90
51.95
69.28
86.40
104.6
121.2
136.3
153.2
164.5
179.4
192.5
208.2
212.1
216.9
222.3
224.3
228.4
230.4
233.3
237.6
240.6
244.4
247.7
251.2
257.0
259.5
264.2
36.73
56.99
77.50
96.30
117.4
135.6
154.9
171.7
188.5
204.2
222.7
236.2
244.1
246.9
253.3
258.2
263.5
268.2
272.2
277.6
281.0
284.5
288.4
292.2
295.6
300.3
302.7
27.10
47.47
71.17
90.31
111.2
129.2
150.5
168.5
180.7
189.5
195.9
199.9
205.6
210.7
215.4
219.0
224.6
228.6
232.9
237.2
242.1
244.9
249.5
253.3
257.8
260.5
263.9
35.28
57.85
81.18
103.78
125.1
144.5
165.9
183.6
200.5
210.9
218.8
224.6
230.2
235.6
240.4
245.6
250.4
254.2
260.0
264.4
268.6
272.8
278.5
280.7
285.9
289.3
292.8
40.53
66.98
94.02
122.4
145.7
168.7
194.9
214.9
234.0
246.7
254.2
261.0
267.9
274.7
281.2
287.4
293.3
298.7
304.6
309.8
315.5
320.3
325.1
332.2
335.3
340.6
345.8
28.69
48.73
66.57
87.30
103.4
120.7
138.4
152.7
162.3
170.1
175.1
180.9
185.9
190.2
194.3
198.5
203.3
207.6
211.1
215.4
218.7
222.4
225.1
227.6
231.1
233.6
236.2
37.68
57.30
76.87
96.52
112.3
129.1
147.9
162.8
177.0
190.4
198.2
203.1
207.5
212.7
215.4
219.7
223.9
227.5
231.1
236.2
240.6
243.7
247.9
251.5
254.5
259.7
262.1
41.18
74.90
99.18
123.3
146.9
171.5
194.3
215.6
228.6
238.0
245.1
252.7
259.4
265.6
272.0
278.2
283.6
290.3
295.9
301.4
306.2
311.1
315.2
320.3
323.9
328.1
331.1
Standard uncertainties (u) are u (M) = 2 * 10−5 mol L−1, u (κ) = 0.002 mS cm−1 and u (T) = 0.1 K.
Table 3
Conductivity values for [C14mim][Br] in the presence of D(+)-Glucose at different molar concentrations and temperatures (T = 298.15 K, 303.15 K and 308.15 K).
[C14mim] [Br]/mM
κ/μS cm−1
0.05 M D(+)-Glucose
T/K
0.25 M D(+)-Glucose
0.50 M D(+)-Glucose
298.15
303.15
308.15
298.15
303.15
308.15
298.15
303.15
308.15
0.26316
0.51948
0.76923
1.01266
1.25000
1.48148
1.70732
1.92771
2.14286
2.35294
2.55814
2.75862
2.95455
3.14607
3.33333
3.51648
3.69565
3.87097
4.04255
4.21053
4.37500
4.53608
4.69388
4.84849
5.00000
5.14852
5.29412
10.15
30.70
52.86
72.24
93.20
110.6
130.2
147.1
163.1
175.3
182.6
188.0
192.9
197.4
201.9
206.1
210.0
213.9
217.6
221.6
224.8
230.6
233.6
237.2
240.2
243.2
247.5
29.56
49.71
72.31
83.34
106.86
125.7
144.0
166.2
186.6
200.2
215.6
222.8
229.3
234.6
240.3
245.5
250.4
255.0
259.5
263.9
266.1
270.5
274.2
277.9
280.4
284.2
287.9
34.26
58.46
83.76
113.1
133.3
159.3
182.8
201.9
222.9
238.5
253.9
261.3
267.3
273.2
278.8
284.2
289.6
294.4
298.8
304.4
308.9
314.4
318.7
324.2
329.1
334.5
339.5
16.15
41.14
61.68
81.68
103.8
124.9
146.1
159.6
166.6
172.9
178.6
184.2
188.8
193.7
199.8
207.4
212.4
215.2
218.9
223.6
227.4
230.8
232.2
235.3
239.4
242.4
245.0
30.10
47.59
71.58
93.38
117.0
138.9
156.0
173.5
190.5
199.0
205.7
211.9
217.8
222.6
227.5
232.0
236.8
241.6
246.0
249.8
253.8
257.1
260.8
264.3
268.1
272.4
275.7
41.39
66.82
89.05
113.9
138.6
161.7
184.4
204.3
221.0
231.5
239.6
246.0
252.1
258.4
264.1
269.6
275.5
280.6
285.0
289.1
293.7
298.5
302.4
306.6
310.7
314.4
319.0
27.15
48.22
67.82
90.09
107.7
126.1
144.5
154.8
161.5
167.5
172.5
177.6
182.2
186.8
191.3
195.9
198.9
203.1
207.2
211.1
214.2
217.9
221.6
225.4
228.7
231.3
234.6
32.64
53.02
75.77
94.25
112.8
132.6
151.5
167.5
179.0
186.0
191.4
197.1
202.1
206.9
211.5
215.9
220.1
224.2
228.2
232.2
235.1
238.6
241.1
245.1
248.3
250.2
253.2
38.21
61.47
84.94
108.7
130.6
152.1
172.9
191.5
205.0
213.3
220.1
226.5
232.6
237.7
243.4
248.0
253.2
257.8
262.7
266.9
270.5
274.8
278.3
283.5
286.2
290.4
293.7
Standard uncertainties (u) are u (M) = 2 * 10−4 mol L−1, u (κ) = 0.0003 mS cm−1 and u (T) = 0.1 K.
5

H. Kumar and R. Kaur
Journal of Molecular Liquids 319 (2020) 114209
of carbohydrate -OH contacts and thus further reducing the conductiv-
ity which accounts for the more decrease in conductivity value of D(+)-
Glucose as compared to D(+)-Xylose.
turn facilitate the formation of micelles. On raising the temperature, mi-
cellization becomes worse which in turn results in an increase in the
CMC value. Two factors are involved when the temperature is raised:
(a) loss of hydration layer around ionic liquid monomers leading to de-
crease in CMC and (b) increase in CMC is caused due to thermal agitation
at higher temperatures is enhanced which limits ionic liquid molecules
to get nearer and form micelles. Thus, the second factor is dominant.
The values of degree of counter-ion dissociation (α) of [C14mim][Br] in
the presence of carbohydrates also decreases in the same order as
CMC values and the order for the ability of investigated carbohydrates
to decrease α value is D(+)-Glucose > D(+)-Xylose which is again in
the same order of the hydrophilicity strength of carbohydrates or their
soluting out strength.
3.1.2. CMC and degree of counter-ion dissociation
The value of the degree of counter-ion dissociation (α) denotes the
average number of counter ions that are bound to the micellar surface
and can be evaluated from the ratio of the post (S2) to pre (S1) CMC
slope values.
α ¼ S2=S1
The slope value variation helps to evaluate α of the system studied
[45,46]. Critical micelle concentration (CMC), an important characteris-
tic for surfactants, is the basic parameter of surface chemistry and it
covers the concentration range where surfactants spontaneously form
micelles [47]. The values of CMC and degree of counter-ion dissociation
(α) for the investigated systems are presented in Table 4. On analysing
the data, we noticed that the values of both critical micelle concentra-
tion (CMC) as well as the degree of counter-ion dissociation (α) are re-
duced on increasing the concentration of carbohydrates for both D(+)-
Glucose as well as D(+)-Xylose while these increases with increase in
temperature. The value of the CMC of ionic liquid [C14mim][Br] in the
absence of carbohydrates is well in agreement with the literature
[48,49].The reasons responsible for the decrease in CMC of ionic liquid
[C14mim][Br] in the presence of D(+)-Glucose and D(+)-Xylose as
additives may be (a) the electrostatic interactions among the charged
head groups of ionic liquid i.e. [C14mim]+ and the -OH groups of
carbohydrates which minimizes the repulsive interactions among the
charged ionic head groups, and (b) the hydrophilic interactions between
carbohydrates and water molecules which results in the distortion of the
water structure in the hydration layer surrounding the ionic liquid head
group and also the hydrophobic tail of ionic liquid. As the CMC values for
the investigated system are decreasing, which implies that the carbohy-
drates decrease the availability of water molecules surrounding the ionic
liquid favouring the micelle formation. Also, the decrease of CMC in case
of D(+)-Glucose is more as compared to D(+)-Xylose for solute-out
strength is related to number of -OH linkages which are more in D
(+)-Glucose (five –OH groups) than in D(+)-Xylose (four –OH groups)
and more number of –OH linkages promotes carbohydrate-water inter-
actions, thus increasing the ionic liquid monomers accessibility which in
3.1.3. Thermodynamics of micellization
CMC of ionic liquid plays a role in Gibb's free energy of micellization.
Therefore, from conductivity measurements, various thermodynamic
parameters of micellization have been computed along with CMC
which helps to understand the thermodynamics of the process under
study. The thermodynamic parameters of micellization include Stan-
dard Gibb's free energy of micellization (ΔG0m), Standard enthalpy of mi-
cellization (ΔH0m) and Standard entropy of micellization (ΔS0m). These
three parameters have been evaluated using the following equations
[2]:
ΔG0m ¼ ð2−αÞRTð lnXCMC
Þ
ð1Þ
ð2Þ
ΔH0m ¼ −RT2ð2−αÞ½dð lnXCMCÞ=dTꢀ
ꢀ
ꢁ
ΔS0m
¼
ΔH0m−ΔG0m =T
ð3Þ
where α is the degree of counter-ion dissociation, R is the universal gas
constant, T is the temperature in Kelvin, XCMC is the mole fraction of
ionic liquid at CMC obtained from conductivity measurements(values
shown in Table 4). Table 5 enlists the calculated values of these thermo-
dynamic parameters of micellization for the ionic liquid [C14mim][Br] in
the absence and in the presence of studied carbohydrates at different
concentrations as well as different temperatures. On examining the
values of ΔG0m evaluated at different concentrations of carbohydrates
and different temperatures from the table, we see that the values have
become more negative in the presence of carbohydrates indicating that
Table 4
CMC and degree of counter ion dissociation α, of ionic liquid [C14mim][Br] in aqueous solution, D(+)-Xylose and D(+)-Glucose at different molar concentrations and temperatures.
Carbohydrate/M
T/K
XCMC
ln XCMC
CMC/mM
α
0 M
298.15
303.15
308.15
298.15
303.15
308.15
298.15
303.15
308.15
298.15
303.15
308.15
298.15
303.15
308.15
298.15
303.15
308.15
298.15
303.15
308.15
5.00E-05
5.17E-05
5.50E-05
4.73E-05
4.99E-05
5.06E-05
3.88E-05
4.01E-05
4.04E-05
3.78E-05
3.96E-05
3.99E-05
4.27E-05
4.63E-05
4.66E-05
3.57E-05
3.97E-05
4.03E-05
3.29E-05
3.88E-05
3.90E-05
−9.903
−9.870
−9.799
−9.958
−9.906
2.780
2.873
3.085
2.632
2.772
2.813
2.158
2.229
2.245
2.101
2.196
2.219
2.371
2.572
2.593
1.983
2.202
2.241
1.830
2.154
2.169
0.309
0.315
0.327
0.305
0.312
0.324
0.303
0.309
0.321
0.301
0.308
0.320
0.291
0.305
0.310
0.287
0.291
0.299
0.286
0.287
0.297
D(+)-Xylose
0.05 M
−9.892
−10.156
−10.124
−10.117
−10.183
−10.139
−10.128
−10.062
−9.981
0.25 M
0.50 M
0.05 M
D(+)-Glucose
−9.973
−10.241
−10.136
−10.119
−10.322
−10.158
−10.151
0.25 M
0.50 M
Standard uncertainties u are u (T) = 0.1 K, u (CMC) = 0.01 mM, u (α) = 0.02.
6

H. Kumar and R. Kaur
Journal of Molecular Liquids 319 (2020) 114209
Table 5
Thermodynamic parameters of micellization of ionic liquid [C14mim][Br] in aqueous solution, D(+)-Xylose, and D(+)-Glucose at different molar concentrations and temperatures.
Carbohydrate/M
T/K
ΔG0m
ΔH0m
ΔS0m
kJ·mol−1
kJ·mol−1
kJ·mol−1·K−1
0 M
298.15
303.15
308.15
298.15
303.15
308.15
298.15
303.15
308.15
298.15
303.15
308.15
298.15
303.15
308.15
298.15
303.15
308.15
298.15
303.15
308.15
−41.501
−41.927
−42.014
−41.844
−42.149
−42.480
−42.726
−43.145
−43.527
−42.879
−43.241
−43.605
−42.639
−42.644
−43.173
−43.483
−43.668
−44.093
−43.863
−43.868
−44.279
−13.501
−13.915
−14.277
−3.220
−3.315
−3.401
−4.939
−5.088
−5.221
−6.859
−7.063
−7.248
−11.319
−11.604
−11.951
−15.492
−15.983
−16.433
−21.554
−22.271
−22.866
0.094
0.092
0.090
0.130
0.128
0.127
0.127
0.126
0.124
0.120
0.119
0.118
0.105
0.102
0.101
0.094
0.091
0.090
0.075
0.071
0.069
D(+)-Xylose
0.05 M
0.25 M
0.50 M
0.05 M
0.25 M
0.50 M
D(+)-Glucose
Standard uncertainties u are u (T) = 0.1 K, u (ΔG0m) = 0.03 kJ·mol−1, u (ΔHm0 ) = 0.02 kJ·mol−1, u (ΔS0m) = 0.02 J·mol−1·K−1
.
the process of micellization has become more spontaneous upon in-
creasing concentrations of carbohydrates and also with increasing tem-
perature. Also, ΔH0m i.e. the standard enthalpy of micellization, is also
negative indicating that the process of micellization is exothermic in na-
ture and the values become more negative at higher concentrations and
at higher temperatures, thermal agitation is enhanced leading to in-
crease in CMC by preventing monomers to come closer. From the values
of ΔG0m and ΔHm0 , the value of standard entropy of micellization ΔS0m has
been calculated using the Eq. (3), which has positive value for the pro-
cess of micellization. The value of ΔS0m has a major contribution towards
ΔG0m and gives information about the process to be entropy driven at a
lower concentration of carbohydrates while enthalpic contribution be-
comes dominant at higher concentrations.
absorption (NA) or negative absorption emission (NAE) phenomenon.
NAE might be due to the light exciting samples from ground states to
lower molecular orbitals, or from ground states to excited states and
then back to lower molecular orbitals, thus producing an emission
that results in A < 0 or T% > 100%. These negative values have been ob-
served in case of water or very negligible concentration of ionic liquid
which is possible because of above mentioned explanation [53].
3.3. FT-IR spectroscopic studies
FT-IR spectroscopic study has been carried out in order to eluci-
date the various interactions taking place in the process of micell-
ization. The FT-IR spectra obtained for the system studied have
been shown in Fig. 5 for [C14mim][Br] in aqueous solution, Fig. 6
(a)–(c) for [C14mim][Br] in the presence of D(+)-Xylose and
Fig. 7(a)–(c) for [C14mim][Br] in the presence of D(+)-Glucose at
selected concentrations (a) below CMC (b) at CMC (c) above CMC
in the wavenumber range 4000–250 cm−1. The important peaks
in the spectra are the two major ones, one is observed at around
3.2. UV–vis spectroscopic studies
The simplest method for evaluating the value of CMC of ionic liquid
in the absence as well as in the presence of carbohydrates is the UV–vis
spectroscopy which is observed in the range of 200–800 nm. The ionic
liquid i.e. [C14mim][Br] is composed of imidazolium ring which is having
the ability to absorb in the UV–vis region prohibits the use of any
external probe [50–52]. The absorbance measurements for the system
studied which comprises of (a) [C14mim][Br] in the absence of carbohy-
drates (b) [C14mim][Br] in the presence of D(+)-Xylose (c) [C14mim]
[Br] in the presence of D(+)-Glucose at different concentrations and
298.15 K temperature were being carried out. The graphical plots for ab-
sorbance versus concentrations have been depicted in Fig. 3 for the ionic
liquid in water and in the presence of D(+)-Xylose and Fig. 4 for the
ionic liquid in the presence of D(+)-Glucose at concentrations 0.05 M,
0.25 M, 0.50 M, and temperature 298.15 K. It is observable from the
plots that the absorbance is first increasing with the increase in the con-
centration of the ionic liquid which then after the particular point is be-
coming almost constant and that particular point is the breakpoint
which signifies the value of CMC of ionic liquid under study [46]. The
values of CMC determined from this technique have been enlisted in
Table 5 which shows that the values are in good agreement with that
obtained using the conductivity technique. Absorbance values mea-
sured for the investigated systems have been presented in Table 6.
From the data it is also observed that few absorbance values are nega-
tive. The reasonable explanation for the negative absorption is a type
of emission phenomenon. The incident light and surrounding environ-
ment excited the sample to produce emission, thus forming a negative
3200–3350 cm−1 and the other one at around 1600–1650 cm−1
.
The shift in wavenumber is observed only in 3200–3350 cm−1 wave-
number region as can be seen from Table 7 indicating that interactions
prevail in the system and this peak corresponds to –N-H str. i.e. means
there occurs H-bonding which is getting affected. The other peak is ob-
served for C_C str. i.e. around 1600–1650 cm−1 which remains almost
unaffected.
3.4. Surface tension measurements
The surface tension method is the versatile technique for obtaining
the information concerning the processes taking place at the interface.
The technique of tensiometry has been utilized to calculate the surface
tension, a key parameter of colloidal science, and it emerges from inter-
face and bulk variations in molecular energy. The surface tension
measurements have been made for the currently studied system of
[C14mim][Br] in the aqueous solution in addition to that in the presence
of carbohydrates at 298.15 K. The plots shown in Fig. 8 have been drawn
from the values of surface tension obtained experimentally (presented
in Table 8) versus the logarithm of concentration of ionic liquid. A pe-
rusal of surface tension values from Table 8, we can observe that surface
tension in the presence of carbohydrates is enhanced in comparison to
the aqueous solution. From the obtained plots, it can be inferred that
7

H. Kumar and R. Kaur
Journal of Molecular Liquids 319 (2020) 114209
Fig. 3. Plots of absorbance versus concentrations of ionic liquid [C14mim][Br] in water and D(+)-Xylose at concentrations 0.05 M, 0.25 M, 0.50 M, and temperature 298.15 K.
Fig. 4. Plots of absorbance versus concentrations of ionic liquid [C14mim][Br] in the presence of D(+)-Glucose at concentrations 0.05 M, 0.25 M, 0.50 M, and temperature 298.15 K.
8

H. Kumar and R. Kaur
Journal of Molecular Liquids 319 (2020) 114209
Table 6
Absorbance values of [C14mim][Br] solutions in the presence of (0,0.05,0.25 and 0.50) M D(+)-Xylose and D(+)-Glucose in the aqueous media.
[C14mim][Br] (mM)
0 M
D(+)-Xylose
0.05 M
D(+)-Glucose
0.05 M
0.25 M
0.50 M
0.25 M
0.50 M
0.0000
0.2632
0.7692
1.2500
1.7073
2.1429
2.5581
2.9545
3.3333
−0.001
−0.001
0.003
0.006
0.008
0.011
0.013
0.014
0.015
−0.160
0.239
0.699
1.312
1.815
2.309
2.387
2.481
2.541
−0.253
0.055
0.734
1.338
2.024
2.491
2.582
2.718
2.797
−0.201
0.032
0.494
0.918
1.362
1.776
2.112
2.259
2.386
0.440
0.720
1.304
1.787
2.269
2.732
2.780
2.794
2.824
0.918
1.218
1.997
2.737
3.299
3.464
3.464
3.464
3.464
0.612
1.056
1.751
2.411
3.014
3.106
3.090
3.093
3.101
Standard uncertainties u are u (T) = 0.1 K, u (M) = 2 * 10−4 mol L−1, u(A) = 1*10−3 mol L−1
.
in the beginning with the increasing concentration of ionic liquid, γ
value decreases till minima is reached since absorption of the ionic liq-
uid molecules at the interface of air-solution lowers down the surface
tension. This minimum corresponds to CMC value as micellization has
started at this point. With more addition of ionic liquid, the value of γ
increases only slowly and remains almost constant afterward. The
various surface parameters such as CMC, surface tension at CMC
(γcmc), surface pressure at the interface (ᴨcmc), the maximum surface
excess concentration (Γmax), and the minimum area per surfactant mol-
ecule at the surface, Amin have been computed from surface tension
measurements using well known Gibb's equation and have been pre-
sented in Table 8. The value of ᴨcmc represents the reduction in surface
tension value to the least possible when the carbohydrates are added
to the ionic liquid solution, and is calculated using the Eq. (4),
πCMC ¼ γ0 ꢁ γCMC
ð4Þ
where γ0 is the surface tension of pure solvent and γcmc is the surface
tension of the investigated system at CMC. Also, the values of other sur-
face active parameters such as maximum surface excess concentration
(Γmax) have been calculated using Gibb's eq. [54] to the obtained data,
ꢂ
ꢃ
∂γ
∂ðlogCÞ
−2:303nRTΓmax
¼
ꢂ
ꢃ
1
∂γ
∂ðlogCÞ
Γmax ¼ −
ð5Þ
2:303nRT
where R is the gas constant, T is the temperature, ∂γ/∂(logC) is the max-
imum slope calculated from the surface tension plots by a linear fit of the
data before the CMC point in which γ is the surface tension and C is the
ionic liquid concentration, n is the number of ionic species existing in
the solution after dissociation in water. Employing the value of Γmax, the
value of minimum surface area occupied by the single ionic liquid mole-
cule at the interface of the solution at CMC can be obtained as [54,55],
1018
NAΓmax
Amin
¼
ð6Þ
where NA is Avogadro's number. On inspection of the values from the
table, we observe that the values of CMC, ᴨcmc and Amin have been de-
creased in the presence of carbohydrates as an additive while the values
of γcmc and Γmax increases. The higher Γmax values in the presence of in-
vestigated carbohydrates indicate an increased packing of ionic liquid
molecules at the air/solution interface [38] and as Amin is inversely pro-
portional to Γmax, which is an effective area of ionic liquid's head group,
is decreased on the addition of carbohydrates. This again shows that in
the presence of carbohydrates, ionic liquid molecules are less solvated
due to more interaction of water molecules with the carbohydrates. As
a result, the micelle formation of ionic liquid molecules is enhanced in
the presence of carbohydrates resulting in lower CMC values. Also, the
thermodynamic parameters such as free energy of the surface at equi-
librium(Gsmin), Standard Gibbs free energy change which is required
for adsorption process (ΔG0ad) have been evaluated using the previously
derived surface-active parameters by making use of following equations
[2,56];
πCMC
Γmax
ΔG0ad ¼ ΔG0m
ꢁ
ð7Þ
ð8Þ
Fig. 5. FT-IR spectra of [C14mim][Br] in the aqueous solution at concentrations: below
CMC, at CMC and above CMC.
Gsmin ¼ Amin
γCMCNA
9

H. Kumar and R. Kaur
Journal of Molecular Liquids 319 (2020) 114209
Fig. 6. FT-IR spectra of solutions in the presence of (a) 0.05 M (b) 0.25 M (c) 0.50 M D(+)-Xylose at concentrations of [C14mim][Br] below CMC, at CMC and above CMC.
10

H. Kumar and R. Kaur
Journal of Molecular Liquids 319 (2020) 114209
Fig. 7. FT-IR spectra of solutions in the presence of (a) 0.05 M (b) 0.25 M (c) 0.50 M D(+)-Glucose at concentrations of [C14mim][Br] below CMC, at CMC and above CMC.
11

H. Kumar and R. Kaur
Journal of Molecular Liquids 319 (2020) 114209
Table 7
tensiometry have been employed. From the results obtained using these
techniques, we conclude that micellization is more favoured in the pres-
ence of carbohydrates (solute-out effect) from the value of CMC which
is lowered more in the case of D(+)-Glucose as compared to D(+)-Xy-
lose. Therefore, the tendency of investigated carbohydrates to enhance
the micellization of the ionic liquid monomers is in the order: D(+)-Glu-
cose > D(+)-Xylose. The reason behind this order is attributed to the in-
crease in the hydrophilicity of carbohydrates which is caused by more
number of –OH groups resulting in more carbohydrate-water molecules
interactions, due to which more ionic liquid monomers are available for
micelle formation. Therefore, the solute-out strength of carbohydrates is
reliant on the number of hydroxyl groups which are more in D(+)-Glu-
cose than in D(+)-Xylose. The various thermodynamic and surface pa-
rameters evaluated using various techniques are in good agreement
with each other and the values of CMC of investigated Ionic Liquid ob-
tained using these techniques are given in Table 10. The negative values
of ΔG0m indicates the spontaneity of the micellization process and the exo-
thermic nature supported by the negative values of ΔH0m.Also, the micell-
ization process is entropy-driven at lower concentrations and enthalpy
driven at higher concentrations of carbohydrates suggested by the con-
ductivity measurements. Therefore, we analysed the surface-active na-
ture of long-chain imidazolium IL [C14mim][Br] is enhanced in the
presence of carbohydrates resulting in their more superior activity in
comparison to that in aqueous solutions. The main aim of our present
study was to study the various interactions taking place between ionic liq-
uid and carbohydrates in aqueous solution which in turn supported the
better micellization behaviour and hence, this study supports the bril-
liance of the novel ways to research further for better alternatives that
can be utilized in a variety of applications.
Wavenumber obtained from FT-IR spectra for ionic liquid [C14mim][Br] in the presence of
(0, 0.05, 0 25 and0 50) M of D(+)-Xylose and D(+)-Glucose at temperature 298.15 K.
Carbohydrate(M)
[C14mim]
[Br]
Wavenumber
(cm−1
)
0
Below CMC
At CMC
Above CMC
Below CMC
At CMC
Above CMC
Below CMC
At CMC
Above CMC
Below CMC
At CMC
Above CMC
Below CMC
At CMC
Above CMC
Below CMC
At CMC
Above CMC
Below CMC
At CMC
3309
3275
3315
3323
3310
3323
3315
3313
3323
3282
3377
3306
3329
3321
3325
3315
3308
3327
3321
3281
3298
D(+)-Xylose
0.05
0.25
0.50
0.05
0.25
0.50
D(+)-Glucose
Above CMC
Their values have also been presented in Table 9. The value for ΔGm0
has been utilized from that obtained in conductivity measurements,
rest have been already discussed. The more negative value for ΔG0ad in
comparison to ΔG0m reveals that the adsorption process is the primary
process taking place in comparison to micellization. Also, the negative
values of ΔG0ad indicate that for the transportation of ionic liquid mono-
mers present at the interface to the micellization stage some work has
to be carried out [57]. On the other hand, lower values of Gsmin suggests
the realization of a highly thermodynamically stable surface due to
which the surface activity is enhanced. Further, in the Table 10 we have
reproted the CMC values obtained from different techniques used in
this study and these values are in good agreement with each other. This
suggests that result obtained using these techniques support each other.
CRediT authorship contribution statement
Harsh Kumar: Conceptualization, Resources, Supervision, Writing -
review & editing. Ramanjeet Kaur: Investigation, Writing - original
draft.
Declaration of competing interest
Authors declare no conflict of interest.
Acknowledgements
4. Conclusions
In order to investigate the influence of carbohydrates on the micelliza-
tion and surface behaviour of [C14mim][Br] in aqueous solutions at
different concentrations and different temperatures, four techniques
comprising conductometric, UV–vis spectroscopy, IR spectroscopy and
Authors (H.K) are thankful to Science and Engineering Research
Board (SERB), New Delhi for providing financial assistance to carry out
Fig. 8. Plots of Surface tension (γ) versus the logarithm of the concentration of ionic liquid [C14mim][Br] in water, D(+)-Xylose and D(+)- Glucose at concentrations 0.05 M, 0.25 M,
0.50 M, and temperature 298.15 K.
12

H. Kumar and R. Kaur
Journal of Molecular Liquids 319 (2020) 114209
Table 8
Surface tension (γ) as a function of the concentration of [C14mim][Br] in the presence of (0, 0.05, 0.25 and 0.50) M of D(+)-Xylose and D(+)-Glucose at 298.15 K in aqueous media.
0 M
D(+)-Xylose
0.05 M
D(+)-Glucose
0.05 M
0.25 M
0.50 M
0.25 M
0.50 M
[C14mim]
[Br]
(mM)
γ
[C14mim]
γ
[C14mim]
γ
[C14mim]
γ
[C14mim]
γ
[C14mim]
γ
[C14mim]
γ
(mN/m) [Br]
(mM)
(mN/m) [Br]
(mM)
(mN/m) [Br]
(mM)
(mN/m) [Br]
(mM)
(mN/m) [Br]
(mM)
(mN/m) [Br]
(mM)
(mN/m)
0
70.42
60.29
54.64
50.99
48.99
46.12
45.73
44.22
42.71
40.27
39.60
38.37
36.05
36.01
35.99
35.98
0
71.24
62.94
56.72
54.60
52.42
50.69
47.31
46.56
44.05
42.11
40.48
40.61
39.32
39.77
39.75
39.75
0
72.48
65.54
61.85
58.08
55.63
53.14
51.35
50.15
47.61
45.20
44.85
44.84
44.82
44.82
44.81
44.80
0
73.56
68.14
63.64
60.18
57.04
55.48
52.73
51.18
49.27
46.47
46.44
46.42
46.41
46.41
46.4
0
71.69
65.58
60.80
56.12
53.42
51.62
48.03
47.35
45.69
43.65
41.42
40.92
40.91
40.90
40.90
40.89
0
72.71
68.81
64.88
61.14
57.08
55.17
52.45
50.30
49.03
48.54
47.89
47.87
47.85
47.85
47.82
47.81
0
73.85
70.19
67.95
63.15
59.59
55.93
53.62
52.24
50.86
49.44
49.20
49.18
49.15
49.15
49.11
49.10
0.10000
0.34286
0.58571
0.82857
1.07143
1.31429
1.55714
1.80000
2.04286
2.28571
2.52857
2.77143
3.01429
3.25714
3.50000
0.10000
0.34286
0.58571
0.82857
1.07143
1.31429
1.55714
1.80000
2.04286
2.28571
2.52857
2.77143
3.01429
3.25714
3.50000
0.10000
0.34286
0.58571
0.82857
1.07143
1.31429
1.55714
1.80000
2.04286
2.28571
2.52857
2.77143
3.01429
3.25714
3.50000
0.10000
0.34286
0.58571
0.82857
1.07143
1.31429
1.55714
1.80000
2.04286
2.28571
2.52857
2.77143
3.01429
3.25714
3.50000
0.10000
0.34286
0.58571
0.82857
1.07143
1.31429
1.55714
1.80000
2.04286
2.28571
2.52857
2.77143
3.01429
3.25714
3.50000
0.10000
0.30714
0.51429
0.72143
0.92857
1.13571
1.34286
1.55000
1.75714
1.96429
2.17143
2.37857
2.58571
2.79286
3.00000
0.10000
0.30714
0.51429
0.72143
0.92857
1.13571
1.34286
1.55000
1.75714
1.96429
2.17143
2.37857
2.58571
2.79286
3.00000
46.39
Standard uncertainties u are u (T) = 0.1 K, u (γ) = 0.01 mN/m.
Table 9
Surface active parameters and thermodynamic parameters of [C14mim][Br] in the aqueous solution, D(+)-Xylose and D(+)-Glucose at different molar concentrations and temperature
298.15 K.
Carbohydrate (M)
CMC (mM)
γcmc (mN/m)
ᴨcmc (mN/m)
106 Γmax (mol/m2)
Amin (nm2)
ΔG0m (kJ mol−1
)
ΔG0ad (kJ mol−1
)
Gsmin (kJ mol−1
)
0
2.78
2.56
2.17
2.07
2.38
1.96
1.81
36.05
39.89
46.03
47.9
41.13
48.01
49.31
34.37
31.35
26.45
25.66
30.56
24.7
2.27
2.49
2.53
2.60
2.69
2.94
3.18
0.73
0.66
0.65
0.64
0.62
0.56
0.52
−41.50
−41.84
−42.73
−42.88
−42.64
−43.48
−43.86
−56.61
−54.40
−53.18
−52.74
−54.01
−51.87
−51.58
15.11
12.56
10.45
9.858
11.37
8.387
7.717
D(+)-Xylose
0.05
0.25
0.50
0.05
0.25
0.50
D(+)-Glucose
24.54
Standard uncertainties u are u (T) = 0.1 K, u (CMC) = 0.01 mM, u (γcmc) = 0.1 mN/m, u (ᴨcmc) = 0.1 mN/m, u (Γmax) = 0.01 μmol/m2, u (Amin) = 0.01 nm2, u (ΔGm0 ) =
0.03 kJ·mol−1, u (ΔGa0d) = 0.02 kJ·mol−1, u (Gsmin) = 0.03 kJ·mol−1
.
research work vide sanction order number EMR/2015/002059.
Ramanjeet Kaur is thankful to University Grants Commission (UGC),
New Delhi for providing Junior Research Fellowship (JRF) (121213) F.
No. 16-6 (DEC. 2017)/2018(NET/CSIR) vide letter UGC-Ref. no.: 131/
(CSIR-UGC NET DEC. 2017). The authors are also thankful to DST, New
Delhi for DST-FIST [CSI-228/2011] Program and The Director and Head,
Department of Chemistry for providing necessary facilities.
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://doi.
org/10.1016/j.molliq.2020.114209.
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