1. PROTON CONDUCTING POLYMER ELECTROLYTES OF CARBOXYL
METHYLCELLULOSE DOPED OLEIC ACID: CONDUCTIVITY AND
IONIC TRANSPORT STUDIES
M.N. Chaia and M.I.N. Isab
Department of Physical Sciences, Faculty of Science & Technology, University Malaysia
Terengganu, 21030 Kuala Terengganu, Terengganu, Malaysia
a
pcmn_1211@hotmail.com, bikmar_isa@umt.edu.my.
Keywords: Solid polymer electrolyte, carboxyl methylcellulose, oleic acid.
Abstract. Solid polymer electrolytes (SPE) of carboxyl methylcellulose (CMC) as the polymer host
and oleic acid (OA) as a dopant were prepared by the solution casting technique. The films obtained
were transparent and no phase separation. The highest ionic conductivity, σ, was found to be 2.11 x
10-5 S cm-1 at room temperature (303 K) for sample CMC-OA 20 wt. %. The ionic mobility and
diffusion coefficient that was calculated in this work is in good agreement with the increment of
weight percent (wt. %) of acid concentration. The value of cation of diffusion coefficient and ionic
mobility was higher than value of anion. Thus, the results proven that the present samples were
proton conductor.
INTRODUCTION
Over the past year, the electrochemical power was obtained by using liquid electrolyte due to its
conductivity. Unfortunately, this liquid electrolyte gives a lot of problem such as leakage, reaction
with electrode, and poor electrochemical stability, which makes it unsuitable for use in electro-
chemical devices [1]. In the world of modern technologies, commercial batteries represent a large
number of toxic and hazardous materials which brings harm to the environment and human health
[2].
In this study, a proton-conducting solid polymer electrolyte or SPEs is presented to overcome this
problem. Electrolyte from cellulose or cellulose derivative is chosen. CMC is a naturally occurring
polysaccharide and the most abundant organic substance on the earth. Due to the abundance, low
cost and easier process ability, so CMC is chosen in this research [3].
EXPERIMENTAL METHOD
2.1 Sample Preparation
1 g of CMC powder was then dissolved in 33 ml distilled water. This solution was stirred for a few
hours until the CMC powder was completely dissolved. Then different weight percentages (wt. %) of
OA was dissolved in 66 ml ethanol then added to the CMC solution and stirred until they dissolved.
The mixtures were then cast into Petri dishes and left to dry at 60 ºC. The films were then kept in
desiccators (with silica gel) for further drying. The compositions of the CMC and OA used are
shown in Table 1.

2. Table 1 Composition of the electrolyte with difference of wt. %
Sample CMC (g) OA (wt. %) OA (g)
OA-0 0 0
OA-5 5 0.0527
OA-10 10 0.1111
OA-15 1 15 0.1765
OA-20 20 0.2500
OA-25 25 0.3333
OA-30 30 0.4286
2.2 Electrochemical impedance spectroscopy (EIS)
Conductivity of the CMC-OA biopolymer electrolytes were measured using the EIS by using the
HIOKI 3532-02 LCR Hi-Tester that was interfaced to a computer in frequency range 50 Hz to 1
MHz. The software controlling the measurement also calculate the real and imaginary impedance.
The films were cut into a suitable size of 2 cm diameter and placed between the blocking stainless
steel electrodes of a conductivity cell which are connected by leads to a computer. The bulk
impedance (Rb) value was obtained from the plot of negative imaginary impedance (Zi) versus real
part (Zr) of impedance and the conductivity of the sample was calculated from the equation 1.
where A = Area of film–electrode contact and t =Thickness of the film (in cm)
2.4 Transference Number Measurement (TNM)
Transference number measurements (TNM) were performed to correlate the diffusion phenomena to
the conductivity behaviour of CMC-OA biopolymer electrolytes. The cation transference numbers, t+
in the electrolytes were determined by monitoring the current as a function of time on application of
a fixed dc voltage (1.5 V) across the sample sandwiched between two stainless steel electrodes.
2.4 Fourier transform-infrared (FT-IR) spectroscopy
A Thermo Nicolet Avatar 380 FT-IR spectrometer was used to analyze the samples. The
spectrometer was equipped with an attenuated total reflection (ATR) accessory with a germanium
crystal. The sample was put on a germanium crystal and infrared light was passed through the sample
with a frequency ranging from 4000 to 675 cm-1 with spectra resolution of 4 cm-1.
RESULTS AND DISCUSSION
3.1 Conductivity study
The σr.t of CMC-OA is depicted in Table 2. The highest σr.t is 2.11 x 10-5 S cm-1 for OA-20. The
increase in the ionic conductivity with increasing OA concentration can be related to the increase in
the number of mobile charge carriers. As the amount of salt added increases, the host matrix became
more crowded with the dopant ions, thus, overcrowding reduces the number of charge carriers due to
limitation of ionic mobility. Hence, the conductivity decreases after 20 wt.% . Figure 1 depicts the
plot of σ versus 1000/T for samples OA-0 to OA-30 from room temperature to 393 K. The linear
variations of the plot suggest an Arrhenius behaviour which implies that the conductivity is influence
by the temperature [4]. The activation energy, was calculated from the slope of the log
conductivity, σ versus 1000/T graph. It can be observed that the value of Ea is inversed to the
conductivity as shown in Figure 2.

3. -3.5 OA-0
-4.0 OA-5
OA-10
Log conductivity, σ
-4.5 OA-15
OA-20
-5.0 OA-25
OA-30
-5.5
-6.0
-6.5
2.4 2.6 2.8 3.0 3.2 3.4
1000/T (K-1)
Figure 1 The temperature dependence for conductivity of CMC-OA electrolyte
2.50E-05 0.45
Conductivity (Scm-1)
2.00E-05
0.40
1.50E-05
Ea (eV)
0.35
1.00E-05
0.30
5.00E-06
0.00E+00 0.25
0 10 20 30 0 10 20 30
Concentration of OA (wt. %) Concentration of OA (wt. %)
(a) (b)
Figure 2 (a) Variation of conductivity as a function of salt content at room temperature and
(b) Variation of activation energy as a function of salt content.
The Rice and Roth model hypothesized that in an ionic conductor there is energy gap, which
conducting ions of mass, could be thermally excited from localized ionic states to free ion like
states in which the ion propagates throughout the solid with velocity, υ. The velocity is given by
Equation 3.
According to Shuhaimi et al. [5], can be considered as the distance between two coordinating sites
or two atoms with the lone pair electrons across which the ions may hop. From this result, the length
of one chain segment was 1.5 nm.
The number density of the mobile ions, , can be expressed by Equation 4.
The ionic mobility, μ, can be calculated as Equation 5.
The diffusion coefficient, D, is given by Nernst- Eistein equation.

4. The calculated parameters is tabulated in Table 3. The conductivity is dependent on ionic mobility
and diffusion coefficient. Further proved of the effect by ionic mobility and diffusion coefficient had
be done by performing TNM.
Table 3 The transport parameters of the CMC-OA biopolymer electrolytes at room temperature
σ x 10-5 x 1022 μ x 10-9 D x 10-11
Sample τ x 10-13 (s)
(S cm-1) (cm-3) (cm2 V-1 s-1) (cm2 s-1)
OA-0 0.04 15.90 1.66 0.01 0.04
OA-5 0.19 9.63 1.79 0.13 0.33
OA-10 0.29 7.55 1.83 0.24 0.62
OA-15 1.19 4.88 1.98 1.53 4.00
OA-20 2.11 2.18 2.12 6.04 15.80
OA-25 1.59 4.09 2.03 2.43 6.40
OA-30 0.50 6.71 1.87 0.39 1.00
3.2 Ionic transport study
When a voltage V, which is below the decomposition potential of the electrolyte is applied to the
cell, ionic migration will occur until steady state is achieved. At the steady state, the cell is polarized
and any residual current flows because of electron migration across the electrolyte and interfaces.
The values obtained was then used to plot the graphs of normalised polarisation current versus time
as shown in Figure 3. The diffusion coefficients of cations and anions in each of the samples were
calculated according to the following equations [6]:
Besides, the ionic mobility can be defined according to the following equation[6]:
where, and is the ionic mobility of cation and anion. The calculated value of , , and
are listed in Table 4.
1.2
Polarisation current, I (A)
1
0.8
0.6 Iion = 0.76
0.4
0.2
0
0 1000 2000 3000 4000 5000
Time, t (s)
Figure 3 Polarization current versus time for samples OA-20

5. Table 4 Ionic mobility and diffusion coefficient of cations and anions
Sample tion μ+ x 10-10 μ- x 10-10 D+ x 10-11 D- x 10-11
2 -1 -1 2 -1 -1 2 -1
(cm V s ) (cm V s ) (cm s ) (cm2s-1)
OA-5 0.65 0.82 0.44 0.21 0.12
OA-20 0.76 45.90 14.50 12.00 3.79
OA-30 0.74 3.40 1.20 0.89 0.31
From the Table 4, it can be observed that the value of the and the is found to be higher than
the value of the and the . These properties of mobility concreted that CMC–OA electrolyte was
a proton conductor.
3.3 FTIR study
All samples prepared are transparent films with no phase separation. The FTIR spectrum of CMC is
quite similar to that given by Abou Taleb et al. & Zaidi et al. [7,8]. The FTIR spectrum of OA is
same as described by Kong et al. [9]. Upon addition of OA, the intensity of the peak increase
gradually with the addition of OA until 20 wt. % indicating that the deprotonation of the OA
increases. Further addition of OA caused the decrease of the peak intensity. This is accommodating
to the values of the conductivity obtained for the samples. The peak at 1710 cm-1 belongs to C=O
stretching of OA. The sharp band around 2920 cm-1 and 2850 cm-1 were assigned to C-H stretching
in asymmetric and symmetric, respectively. The band at 1597 cm-1 confirmed the presence of COO¯
was assigned to stretching of the carboxyl group. The IR spectrum of CMC showed the band at 1040
cm-1 was characteristic of the C-O stretching on polysaccharide skeleton. The intensity of the peak
increases with the addition of OA as shown in Figure 4.
OA- 30
2850
2920
OA- 25
OA- 20
% Transmitance
OA- 15
OA- 10
OA- 5
OA- 0
1597
3100 2400 1700 1000
Wavenumber (cm-1)
Figure 4 FTIR spectrum of the sample in the region between 1000 and 3100 cm-1

6. Based on Figure 4, it can be shown that peak intensityof H+ (2920 cm-1 and 2850 cm-1) of OA is
increases whereas the peak of COO- (1597 cm-1) of CMC was less obvious with the addition of OA.
It is suggested that protonation occurred in the present samples and the interactions between CMC
and OA existed.
CONCLUSION
The CMC-OA biopolymer electrolyte obtained the highest conductivity of 2.11 x 10-5 S cm-1 at room
temperature for sample OA-20 with OA concentration of 20 wt. %. By using Rice and Roth model,
conductivity of CMC–OA biopolymer electrolyte is not only caused by the increase in the
concentration but also by the increase in ionic mobility and diffusion coefficient. From the TNM, it
is proven that the sample is a proton conductor where the value of μ+ and D+ is found to be higher
than the value of μ- and D-. Thus, this prove that the present samples were proton conductor. The
conductivity is still low compared to the current conductivity based on polymer, it can be enhanced
with the addition of plasticizer.
ACKNOWLEDGEMENT
The authors would like to thank the Department of Physical Sciences under the Faculty of Science
and Technology, University Malaysia Terengganu, for the help and support given for this work.
REFERENCES
[1] Idris, N.K., Nik Aziz, N.A., Zambri, M.S.M., Zakaria, N.A. & Isa, M.I.N. 2009. Ionic conductivity
studies of chitosan- based polymer electrolytes doped with adipic acid. Ionics 15: 643-646.
[2] Fonseca, C.P., Rosa, D.S., Gaboardi, F. & Neves, S. 2006. Development of a biodegradable polymer
electrolyte for rechargeable batteries. Journal of power source 155: 381-384.
[3] Siddhanta, A.K., Prasad, K., Meena, R., Prasad, G., Mehta, G.K., Chhatbar, M.U., et al. 2009. Profiling
of cellulose content in Indian seaweed species. Bioresource Technology 100: 6669-6673.
[4] Khiar, A.S.A., Puteh, R., & Arof, A.K. 2006. Conductivity studies of a chitosan-based polymer
electrolyte. Physica B 373: 23-27.
[5] Shuhaimi, N.E.A., Teo, L.P., Majid, S.R. & Arof, A.K. 2010. Transport studies of NH4NO3 doped
methyl cellulose electrolyte. Synthetic Metals 160: 1040–1044.
[6] Tan, W. & Arof, A.K. 2005. FT-IR studies on interactions among components in hexanoyl chitosan-
based polymer electrolytes. Spectrochimica Acta Part A 63: 677-684.
[7] Abou Taleb, M.F., Abd El-Mohdy, H.L. & Abd El-Rehim, H.A. 2009. Radiation preparation of PVA/
CMC copolymers and their application in removal of dyes. Journal of harzadous materials 168: 68-75.
[8] Zaidi, W., Oumellal, Y., Bonnet, J.P., Zhang, J., Cuevas, F., Latroche, M., et al. 2011.
Carboxymethylcellulose and carboxymethylcellulose-formate as binders in MgH2–carbon composites
negative electrode for lithium-ion batteries. Journal of Power Sources 196: 2854–2857.
[9] Kong, S., Zhang, P., Wen, X., Pi, P., Cheng, J., Yang, Z., et al.. 2008. Influence of surface modification
of SrFe12O19 particles with oleic acid on magnetic microsphere preparation. Particuology 6: 185-190.