Materials Sciences and Applications, 2011, 2, 1639-1643
doi:10.4236/msa.2011.211218 Published Online November 2011 (
Copyright © 2011 SciRes. MSA
Structural and Conductivity Studies of
Poly(Ethylene Oxide)—Silver Triflate Polymer
Electrolyte System
Nirali Gondaliya1,2, Dinesh Kumar Kanchan1*, Poonam Sharma1, Prajakta Joge1
1Physics Department, Faculty of Science, M. S. University of Baroda, Vadodara, India; 2Department of Engineering Physics, Bha-
ruch, India.
Email: *
Received June 22nd, 2011; revised August 1st, 2011; accepted August 15th, 2011.
Films of PEO containg AgCF3SO3 were prepared by the solution casting technique. Fourier transform infrared (FTIR)
spectroscopy has been carried out on a series of complexes containing poly(ethylene oxide) PEO and silver triflate
(AgCF3SO3) salt. Spectral analysis of all the samples has revealed the complexation of silver ions with oxygen in PEO.
The ac conductivity and electrical modulus of the prepared samples have been analyzed. The ac conductivity was ob-
served to obey the Universal power law. The temperature dependence of the power law exponent n is reasonably inter-
preted by the overlapping large polaron tunneling (OLPT) model. The imaginary part, M" of electrical modulus shows
the formation of dispersion peak. The plot of log conductivity relaxation times and log conductivity as a function of salt
concentration was in accordance with each other.
Keywords: PEO-AgCF3SO3, FTIR, Conductivity, Modulus
1. Introduction
Polymer based solid electrolytes are one of the most ex-
tensively studied systems. PEO is widely used as host
polymer because of its ability to dissolve a wide variety
of metal salt, good mechanical properties compared with
those of other polymer host [1,2]. Interestingly, silver ion-
conducting polymer electrolytes based on PEO appear to
be the most appropriate choice for various electrochemi-
cal applications [3]. As stated by most experimental work,
cation mobility occurs in the amorphous phase and its
diffusion occurs through a complex mechanism involv-
ing the PEO segmental mobility. For that, crystallization
has to be avoided by modifying the polymer structure or
by adding salts to inhibit regular packing. Moderate con-
ductivity in amorphous materials is then a direct conse-
quence of PEO features where high salvation is counter-
balanced by the energetic complexation of cations. Su-
thanthiraraj et al. reported enhancement in conductivity
in silver based PEO polymer electrolytes due to incorpo-
ration of nano-fillers [4]. There was an increased thrust
during the last decade towards investigating new matri-
ces for improving ion-conducting characteristics as well
as their detailed structural characterization by means of
fourier transform infrared (FTIR) spectral features. In the
present work we intend to study the effect of silver salt
concentrations in PEO-based polymer electrolytes by
means of vibrational spectroscopy and complex imped-
ance analysis.
2. Experimental
The solution was prepared by dissolving weighted per-
centage of PEO {with an average molecular weight of
M.W 1,000,000, Sigma-Aldrich} and various concentra-
tion of Silver trifluromethane Sulphonate (AgCF3SO3)
[(x = 2 wt%, 3.5 wt%, 5 wt%, 7 wt%, 11 wt%){purity >
99%, Aldrich}] in an acetonitrile solution {used as sol-
vent obtained from MERCK}. This mixture was con-
stantly allowed to stir for 48 hours at ambient tempera-
ture. Any contamination with the external ambient was
carefully avoided by performing all the preparation steps
in a controlled environment. The homogenous and vis-
cous solution was cast in PTFE plates. Solvent evapora-
tion was carried out in closed apparatus for 24 to 30 hours
at ambient temperature. Next, the dried film so obtained
was hot-pressed in a polymer press by specially made
stainless steel die (20 μm - 50 μm thickness) by applying
Structural and Conductivity Studies of Poly(Ethylene Oxide)—Silver Triflate Polymer Electrolyte System
10 tons pressure at 65 ± 5˚C (338 K) for 10 min. Semi-
transparent homogeneous membranes having thickness
ranging from 10 - 30 μm and good mechanical strength
were obtained.
Vibrational spectroscopy was carried out using JASCO
4100 series FTIR spectrophotometer in the wave number
ranging from 500 to 3000 cm–1. For the impedance mea-
surement, the polymer electrolytes film was sandwiched
between two silver blocking electrolytes with diameter 1
cm, under spring pressure. Impedance spectroscopy was
taken using the Solartron 1260 Impedance Gain/Phase
Analyser in the frequency range of 10 MHz to 10 Hz
frequency range. The cell temperature was controlled us-
ing a thermometer in the temperature range of 303 K to
328 K.
3. Result and Discussion
3.1. FT-IR
Figure 1 represents the FTIR spectra for pure PEO, and
PEO-AgCF3SO3 films. For pure PEO, C-H stretching
mode can be observed at 2876 cm1, CH2 scissoring
mode at 1466 cm1, CH2 wagging mode at 1360 and
1341 cm1, CH2 twisting mode at 1279 cm1, C-O-C stre-
tching at 1104, CH2 rocking and C-O-C vibration mode
at 960 cm1, CH2 rocking at 841 cm1 while C-O-C ben-
ding at 528 cm1. The semi-crystalline phase of PEO is
confirmed by the presence of triplet peak of C-O-C stre-
tching [5,6]. C-O-C stretching vibrations are observed at
1145, 1095 and 1059 cm1 with maximum intensity at
1095 cm1 [7]. Complexation of silver salt with PEO can
be confirmed on the appearance of the peaks at 636 cm1
which may be assigned to the s (SO3) mode of free tri-
flate ion. It is also evident that the formation of the asso-
ciated peak at 1028 cm1 corresponds to the SO3 symmetric
mode [3]. The spectral features observed in the range of 945
Figure 1. IR spectra at room temperature.
- 836 cm1, for all the samples including pure PEO, suggest
that the symmetrical rocking mode of CH2 group has not
been affected by complexation with AgCF3SO3.
3.2. Frequency Dependent Conductivity
It can be observed from Figure 2 that the ionic conduc-
tivity of the polymer electrolyte increases with increasing
salt content up to 7 wt% and thereafter the conductivity
decreases. The increase in conductivity with salt concen-
tration could be attributed to the increase in the number
of mobile ions as a result of salt concentration [8]. Addi-
tion of salt increase the amorphous structure of the
polymer (as evident from the FTIR) through favorable
free volume and therefore, ion migration takes place eas-
ily [9]. However, with the further increase in salt con-
centration, these ions come closer to one another which
are attributed to salt re-association and hence conductiv-
ity decreases [10]. A typical plot of ac conductivity as a
function of frequency for 5 wt% AgCF3SO3 is shown in
Figure 3. Ac conductivity is observed to increase with
Figure 2. Variation of log () and log () for different salt
Figure 3. Plot of ac conductivity (5 wt% AgCF3SO3).
Copyright © 2011 SciRes. MSA
Structural and Conductivity Studies of Poly(Ethylene Oxide)—Silver Triflate Polymer Electrolyte System1641
temperature and its flattened portion curve also increases
with temperature. At the mid frequency region, the con-
ductivity increases continuously because at that frequen-
cy, the charge carrier gets excitation energy from the
electrical signal. Due to this excitation energy, the mobi-
lity of the charge carrier increases which in turn, de-
creases the relaxation time and thus, the conductivity in-
creases. The nature of conductivity behavior observed can
be explained using Jonscher’s Universal power law [11]
 
 (1)
where, σdc is the dc conductivity of the sample, A is a
constant for a particular temperature and n is the power
law exponent. The value of n was calculated from the
slope of the log(σ σdc) vs. lo gω, which is a straight line.
The values of exponent n were ranging from 0.5 to 0.9,
i.e., less than 1 and were observed to decrease with tem-
perature for all AgCF3SO3 concentration. It means that
the increase in conductivity can also be ascribed to the
increase in degree of disorder in the materials on com-
plexation with salt. It is observed (Figure 4) that expo-
nent n decreases with increasing temperature, exhibits a
minimum at a certain temperature after which it begins to
increase. This may due to breaking of internal correlation
between the sites and relaxing ions and relaxing species
become independent of each other which results in tun-
neling process rather than hopping. Therefore the over-
lapping large polaron tunnelling (OLPT) model is best
suitable to explain the conduction process in the present
study [12-14].
3.3. Modulus
To study the electrode effect in the system, we have ana-
lyzed the dielectric spectra by complex electric modulus
Figure 4. Variation of exponent n with temperature for
AgCF3SO3 7 wt% and 11 wt%.
[15]. The complex electric modulus can be evalu-
ated from the following relations.
 
 
 
 
 
 
The frequency dependence of
PEO-AgCF3SO3 3.5 wt% is shown in Figures 5 and 6
respectively. The plot shows the features of ionic con-
duction (an S shaped dispersion in
and a peak in
[16]. The peak in
 can be assumed to be re-
lated with the translational ion dynamics and mirrors the
conductivity relaxation of the mobile ions. It is worth
noticing that the relaxation peak which is responsible for
fast segmental motion. This fast segmental motion of po-
lymeric chain reduces the relaxation time and increases
the transport properties. From the condition max
is the relaxation time for the ionic charge car-
rier is estimated [17]. The variation of conductivity log
and relaxation time log as a function of salt AgCF3SO3
at 313 K is given in Figure 2. The conductivity increases
nonlinearly till 7 wt% of AgCF3SO3 and then decreases at
11 wt% of the salt. This anomaly is also observed for the
variation of relaxation time, log where the relaxation
1f is observed to decrease and suddenly in-
creases for 11 wt% of AgCF3SO3.
Figure 5. Variation of real part of electric modulus (M)
with log f at different temperature for AgCF3SO3 3.5 wt%.
Copyright © 2011 SciRes. MSA
Structural and Conductivity Studies of Poly(Ethylene Oxide)—Silver Triflate Polymer Electrolyte System
Figure 6. Variation of imaginary part of electric modulus
(M) with log f at different temperature for AgCF3SO3 3.5
The plotting of ac data in terms of impedance, electric
modulus and dielectric permittivity simultaneously is ex-
tremely advantageous for distinguishing the different
relaxation processes occurring inside the materials. The
comparison of the experimental data in the M* and ε*
formalism is, therefore, useful to distinguish long-range
conduction process from the localized dielectric relaxa-
tion. To visualize this, we have plotted the imaginary part
of complex dielectric permittivity (ε) and modulus (M)
as a function of frequency for PEO-AgCF3SO3 (7 wt%)
polymer electrolyte (Figure 7). Dielectric relaxation is a
result of the reorientation process of dipoles in the poly-
mer chains, which show a peak in ε spectra. For elec-
trolyte with higher ion concentration, the movement of
ions from one site to another perturbs the electric poten-
tial of the surroundings. Motion of the other ions in this
region will be affected by perturbed potential. This type
of cooperative motion of ions exhibits non-exponential
decay, or a conduction processes with distribution of re-
laxation time [18]. In the imaginary part of modulus spec-
tra, a relaxation peak is observed (for the conductivity
processes), whereas no peak was seen in the dielectric
spectra. This suggests that ionic and polymer segmental
motion is strongly coupled and hence manifesting as a
single peak in the M spectra with no corresponding fea-
ture in dielectric spectra [19].
4. Conclusions
PEO-AgCF3SO3 samples are principally ionic conductors.
Even a small dispersion of the silver salt causes an en-
hancement in the conductivity in comparison to pure po-
lymer. The complexation of salt with polymer has been
confirmed using FTIR studies. The electrical modulus re-
presentation of the same data shows a loss feature in the
Figure 7. Plot of the imaginary part of ε and modulus (M)
as a function of frequency for AgCF3SO3 7 wt% at 313 K.
imaginary component. The relaxation associated with this
feature shows a stretched exponential decay. The analysis
of frequency dependence of dielectric and modulus for-
malism suggests that the ionic and polymer segmental
motion are strongly coupled manifesting as a single peak
in the M spectra with no corresponding feature in di-
electric spectra. The frequency dependent of ac conduc-
tivity follows Jonscher’s power law feature and the low
frequency dispersion indicating the presence of electrode
polarization phenomena in the materials.
5. Acknowledgements
One of the authors PS thankfully acknowledges the fi-
nancial support by UGC, New Delhi, India for RFSMS
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