A. Mehrdad et al. / Journal of Molecular Liquids 216 (2016) 12–17
15
Fig. 5. The plots of Lnη versus reciprocal temperature (1 / T) for PEO solutions in [IL] =
0.0044 mol·kg−1 at various weight fractions of polymer (wp): ♦ 100wp = 0.0000; ◊
100wp = 0.0502 ; ● 100wp = 0.1010; ○ 100wp = 0.1513; ▲ 100wp = 0.2008; Δ
100wp = 0.2497; ■ 100wp = 0.2960; □ 100wp = 0.3470.
Fig. 4. The plots of reduced viscosity (ηred) versus polymer concentration (C) for PEO
solutions in [IL] = 0.0044 mol·kg−1: ♦ T = 288.15 K; ◊ T = 293.15 K; ● T = 298.15 K;
○ T = 303.15 K; ■ T = 308.15 K; □ T = 313.15 K.
was kept constant by a temperature controller (Lab. Companion, RW-
0525G, Jeio tech Co.) with a precision of 0.05 K. The flow time of solu-
tions was measured with an uncertainty of 0.2 s. The densities of the
solutions were measured using a vibrating tube densimeter (Anton Paar
DSA-5000, Austria). The accuracy of density measurements was better
than 3 × 10−3 kg·m−3. The apparatus was calibrated with doubly
distilled deionized and degassed water followed by dry air at atmo-
spheric pressure.
2.3. Apparatus and procedure
In FT-IR analysis, PEO and [HMIm]Br were dissolved in acetonitrile,
and the blends were casted onto the KBr pellets. PEO/ionic liquid solu-
tions were prepared with varying compositions (25/75, 50/50, 75/25
w/w). Thin films of samples were dried under vacuum for 24 h then an-
alyzed by FT-IR spectroscopy. FT-IR spectra were recorded using a
Bruker Tensor 27 spectrometer in the wave number range of 400–
4000 cm−1. For UV–Vis analysis, aqueous ionic liquid/PEO solutions
were prepared at different compositions (1/0, 0.32/1, 1.2/1 and 2.6/1
w/w) using double distilled water. The UV–Vis spectra were recorded
using a UV–Vis spectrophotometer (T80, PG Instrument Ltd).
3. Results and discussion
3.1. Fourier transform infrared spectroscopy
In viscometric analysis, the ionic liquid solutions at different concen-
trations (0.0044, 0.0125, 0.0204 mol·kg−1) were prepared using double
distilled water. The polymer solutions were prepared at the concentra-
tion range of 0.5 to 3.5 kg·m−3 using double distilled water and pre-
pared ionic liquid aqueous solutions. The weightings were performed
on a Sartorius analytical balance (CP224 S) with an uncertainty of
1 × 10−7 kg. The solutions were filtered before use by a filter with
aperture of 75 μm and their viscosity was measured using a jacketed
Ubbelohde viscometer with 0.4 mm capillary at a temperature range
of 288.15–313.15 K. The flow time was determined from an average of
several readings (at least 3 readings). The temperature of solutions
FT-IR spectra of IL, polymer and Polymer/IL blends are shown in Figs.
S1–S5 (supporting information). The absorbance peaks for stretch
frequencies of the C–O bond in PEO have been observed at 1000–
1200 cm−1. In this region, the spectrum shows a triplet peak. The cen-
tral peak of the triplet is at 1112 cm−1. The FT-IR spectra of IL and
PEO blends in the region of C–O stretching vibrations are shown in
Fig. 1. From Fig. 1, it can be seen that the C–O stretching vibration in
Polymer/IL blends was red-shifted by approximately 11 cm−1 in com-
parison to the pure PEO. The FT-IR spectra of IL and PEO blends in the
region of C–H stretching vibrations are shown in Fig. 2. The bands corre-
sponding to stretching vibrations of the C–H bonds in IL have been
observed at 2800–3200 cm−1. In this region, the spectrum shows five
peaks. The imidazolium cation has eight type C–H bonds and PEO has
one type C–H bond which are depicted in Scheme 1. The observed
peak at around 2858 cm−1 is ascribed to C6–H of IL and C–H of the poly-
mer. The observed peak at around 2930 cm−1 is attributed to C7–H of IL.
The observed peak at around 2957 cm−1 is attributed to C8–H, C9–H,
Table 4
The obtained intrinsic viscosity values ([η])a and interaction parameter of Huggins, (bH)a,
of PEO in aqueous solutions of IL on the basis of Eq. (2).
T/K
[IL] = 0.0000
mol·kg−1
[IL] = 0.0044
mol·kg−1
[IL] = 0.0125
mol·kg−1
[IL] = 0.0204
mol·kg−1
[η]/m3·kg−1
288.15
293.15
298.15
303.15
C
10–H, C11–H and C12–H of IL. The observed peak in wavenumber
0.6368
0.6114
0.5817
0.5539
0.5233
0.4425
0.6351
0.6095
0.5810
0.5521
0.5214
0.4532
0.6355
0.6022
0.5728
0.5426
0.5167
0.4489
0.6301
0.6025
0.5735
0.5473
0.5178
0.4399
around 3063 cm−1 is ascribed to C2–H of IL. Also the peak at around
3138 cm−1 is ascribed to C4–H and C5–H of IL. The hydrogen of C2–H
is significantly acidic; therefore in imidazolium based IL may be a com-
bination of hydrogen bonding and coulombic attraction between cation
and anion [10]. In the case of PEO, the oxygen atom is a potential hydro-
gen bond acceptor [23]. By considering the some hydrogen bonds
between cation and anion are replaced with hydrogen bond between
cation and oxygen atom by addition of PEO to IL; therefore the absor-
bance peaks of the C2–H stretching vibrations are shifted. The hydrogen
bond interaction between imidazolium cation and polyethylene oxide is
depicted in Scheme 1. Fig. 2, indicated that C2–H stretching vibrations in
Polymer/IL blends were blue-shifted by approximately 14 cm−1 in
308.15
313.15
bH/m6∙kg−2
288.15
293.15
298.15
303.15
0.1582
0.1453
0.1350
0.1246
0.1145
0.0993
0.1601
0.1490
0.1388
0.1303
0.1221
0.1002
0.1579
0.1474
0.1384
0.1285
0.1195
0.0967
0.1570
0.1458
0.1338
0.1233
0.1156
0.1002
308.15
313.15
a
Standard uncertainties u are u([η]) = 0.0048 m3·kg−1, u(bH) = 0.0022.
Mehrdad, Abbas
