Thermal, structu ral, optical and electrical properties of PVA/MAA:EA polymer blend fi lled with different concentrations of Lithium Perchlorate

Journal of Science: Advanced Materials and Devices 3 (2018) 456e463

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Journal of Science: Advanced Materials and Devices
journal homepage: www.elsevier.com/locate/jsamd

Original Article

Thermal, structural, optical and electrical properties of PVA/MAA:EA
polymer blend filled with different concentrations of Lithium
Perchlorate
T. Siddaiah a, Pravakar Ojha a, N.O. Gopal a, Ch. Ramu a, *, H. Nagabhushana b
a
b

Department of Physics, Vikrama Simhapuri University PG Centre, Kavali, 524201, India
CNR Rao Centre for Advanced Materials Research, Tumkur University, Tumkur, 572103, India

a r t i c l e i n f o

a b s t r a c t

Article history:
Received 18 July 2018
Received in revised form
17 November 2018
Accepted 18 November 2018
Available online 27 November 2018

Structural, optical, thermal and morphological studies were performed on pure Polyvinyl alcohol/

Methacrylic Acid e Ethyl Acrylate (PVA/MAA:EA (50:50)) blend and PVA/MAA:EA blend filled with
different concentrations (5, 10 and 15 wt%) of Lithium Perchlorate (PVA/MAA:EA: LiClO4) prepared by a
solution casting method. XRD patterns demonstrated that the peak intensity at 2q ¼ 19.5 decreased and
the bandwidth increased with increasing the concentration of LiClO4, which implied a decrease in the
degree of crystallinity and hence caused an increase in the amorphous nature. UV e Visible analysis
revealed that the values of both direct and indirect band gaps were decreased with increasing LiClO4
content in the polymer host. This indicated the formation of charge transfer complexes between the
polymer blend and the filler. The dTGA curves show three different steps of weight loss. This is due to the
loss of water adsorbed, the elimination of the side chains, and the decomposition of the main chain. For
LiClO4 filled PVA/MAA:EA, FTIR spectra showed disappearance of some bands with the change in their
intensities as compared to pure PVA/MAA:EA film. This indicated considerable interaction between the
polymer blend and LiClO4 filler. SEM images of the polymer blend films complexed with LiClO4 suggested
the presence of a structural rearrangement of the polymer chains. The electrical conductivity of the
prepared films was measured using the impedance analyzer in the frequency range from 1 Hz to 5 MHz
at room temperature. It was observed that the conductivity increased with increase of the Liþion
concentration.
© 2018 The Authors. Publishing services by Elsevier B.V. on behalf of Vietnam National University, Hanoi.
This is an open access article under the CC BY license ( />
Keywords:
Polymer
Lithium Perchlorate
PVA/MAA:EA blend
FTIR
TGA
X e ray
SEM and optical energy

1. Introduction
Nowadays, the rechargeable battery market is about 27.7 billion
dollars and in 2019 it has been assessed to be 54.9, a fast growth is

expected in the rechargeable battery market due to the increase in
the demands such as laptops, mobile phones, e-books, watches,
toys, automotive sectors and transportation [1]. Liþ ion batteries are
dominant in the electronic devices market due to their compact
and lightweight, safety, reliability, cost, design, efficiency, being
more environmentally friendly, the highest energy density, high
average discharge rate (~37 V) and the absence of memory effects
among other types of batteries [2e4].

* Corresponding author.
E-mail address: (Ch. Ramu).
Peer review under responsibility of Vietnam National University, Hanoi.

Materials based on the polymers originate from the need for
self-standing, leak-free battery systems. The three types of polymer
materials are single polymer electrolyte (SPE), composite polymer
electrolyte (CPE) and polymer blend electrolyte (PBE). In PBE, two
different polymers having complementary properties i.e. one
polymer showing good affinity with the liquid electrolyte and the
other showing proper mechanical properties are used. The most
used polymer blend electrolytes are (PVA e PANI), (PVA e PAN),
(PVP e PVA), (PMVEMA e PVA), (PVA e PEI), (PVA e PVdF), (PEO e
PVA), (PVA e PAA), (PVA e PEG), (PEO e PMMA), (PVC e PS),
(Chitosan e PVA), (PVA e NyC), (PEMA e PVdF), (PVA e NaAlg) and
its copolymers P(VDF e TrFE), P(VDF e HEP) and P(VDF e CTFE).
There has been considerable interest in polymer blends in
recent decades, owing to their better combination of physical
properties, biocompatibility and potential applications than those
of single components [5,6]. It is generally recognized that the
properties of the polymer blends are greatly dependent on their

/>2468-2179/© 2018 The Authors. Publishing services by Elsevier B.V. on behalf of Vietnam National University, Hanoi. This is an open access article under the CC BY license
( />

T. Siddaiah et al. / Journal of Science: Advanced Materials and Devices 3 (2018) 456e463

miscibility and phase behavior. When two polymers experience
miscibility, a well-ordered microstructure is obtained, which gives
the mixture certain unique physical properties according to the
formation of the microphase configuration. The resulting microphase configuration can induce drastic changes in all the properties (Optical, thermal, electrical…etc.) that are different from those
of the individual polymers. Therefore, the miscibility and phase
behavior of polymer blends have been the subject of numerous
studies [7].
Polyvinyl alcohol (PVA) has received a great deal of attention
due to its high dielectric strength, good charge storage capacity and
dopant dependent electrical properties either pure or composite
with other materials [8]. PVA is well known for its low cost,
excellent transparency, flexibility, toughness, nontoxicity, water
solubility, biodegradability and gas barrier properties. Hence, it is
widely used in controlled drug delivery systems, membrane preparations, recycling of polymers, packaging textiles and leather industries because of excellent film-forming characteristics. The
optical uses of PVA are related to the delay, polarization and
filtering of light and to photography [9].
Methacrylic Acid e Ethyl Acrylate (MAA:EA) copolymer has
been placed at the center amongst the copolymers due to its advantages like easier processability, good environmental stability
and transparency. It has substantial charge storage capacity and
dopant dependent electrical and optical properties. Acrylates are a
group of easily UV- polymerizable monomers with an unending
possibility of polymer chain compositions which can thus be
optimized to meet the desired material properties. Different types
and amounts of selected monomer units, the length and composition of the main polymer chain as well as chemistry of the side

chains can be varied and the polymer structure can be further
altered by cross-links [10,11].
In order to benefit from the advantages of the polymer and
copolymer, in this work, PVA and MAA:EA have been blended at a
fixed weight ratio of 50:50 and Lithium has been added to provide
the charge carriers. Blended host matrices also help to increase
ionic conductivity [12]. Both PVA and MAA:EA contains electron
pairs that can coordinate with a cation from inorganic salt like Liþ to
form polymer-salt complexes and hence produce ionic conduction.
Electron pairs are formed on oxygen atoms of C ¼ O and C e O e C
groups of PVA and hydrogen atoms in MAA:EA copolymer [13].

457

0.02 between 0 and 40 . FTIR spectra of the prepared samples
were recorded using a PerkineElmer FTIR spectrometer, over a
wavenumber range 500e4000 cmÀ1. SEM images of the polymer
blend electrolyte films were characterized by Hitachi (TM e 3000
and H e 8100) electron microscope with scanning attachment. The
optical absorption curves of the films were recorded in the range of
200e800 nm at room temperature using JASCO UV e VIS e NIR
spectrophotometer (model e V.700). The electrical properties of
the polymer electrolyte films were studied using a Hitester 3532-50
LCR in the frequency range of 1 Hze5 MHz.
3. Results and discussion
3.1. X-ray diffraction analysis
X-ray diffraction analysis provides useful structural information,
such as crystal structure, crystal size, strain, preferred orientation
and layer thickness of a tested material. Researchers used the X-ray
diffraction to analyze a wide range of materials such as powders,

thin films, nanomaterials and solid objects. Fig. 1 shows the XRD
scans of pure PVA/MAA:EA (50:50) blend and PVA/MAA:EA blend
filled with various weight fractions (5, 10 and 15 wt%) of Lithium
Perchlorate (LiClO4) filler. The observed diffractograms exhibit
three peaks centered at about 2q ¼ 19.5 , 1.4 and 0.6 , which indicates the semi-crystalline nature of the PVA/MAA:EA polymer
blend film [14]. The first one has a clear crystalline peak at a scattering angle 2q ¼ 19.5 which corresponds to a (1 1 0) reflection
[15]. The present X-ray pattern revealed no significant changes in
the positions of three peaks after complexation with filler, the intensity of the diffraction peaks is further decreased. This could be
due to the interaction between the blend and filler, leading to
decrease in the intermolecular interaction between the blend
chains as well as the degree of crystallinity [16]. As the Liþ content
is increased in the polymer, the diffraction peaks become less
intense, suggesting a decrease in the degree of crystallinity and a
simultaneous increase in the amorphicity of these polymer electrolyte systems. The decrease in crystallinity with increasing LiClO4
content in the blended sample involves a decrease in the number of

2. Experimental
MAA: EA copolymer (1:1) dispersion of 30 percent is a dispersion in water of a copolymer of Methacrylic Acid and Ethyl Acrylate
having an average relative molecular weight of about 250,000
(supplied by Merck Millipore India Ltd.) and high purity. PVA of
molecular weight 17,000 in form of grains was provided by Merck C
Darmstadt, Germany. Films of (thickness ~ 150 mm) pure PVA/
MAA:EA and different compositions of LiClO4 complexed films of
(PVA/MAA:EA) were prepared by the solution cast technique in
different weight percent ratios (50.0:50.0:0), (47.5:47.5:5),
(45:45:10), (42.5:42.5:15) using double distilled water as a solvent.
Required amounts of PVA, MAA: EA and LiClO4 were dissolved in
double distilled water and the solutions were stirred magnetically
for 10e12 h to obtain a homogeneous solution and then poured into
polypropylene dishes and evaporated slowly at room temperature

for 48 h to obtain free-standing pure and doped films at the bottom
of the dishes. The thermal properties of the prepared samples were
studied using SEIKO thermal analysis system (TGA e 20) in the
presence of nitrogen flow from 40 to 700  C, at the heating rate of
10  C/min. The X-ray diffraction patterns were performed using a
Siemens D5000 diffractometer with CuKa radiation (l ¼ 1.5406 Å).
The prepared films were scanned at 2q angles with a step size of

Fig. 1. XRD patterns of (a) pure (50:50) and different concentrations (b) 5 wt% (c)
10 wt% and (d) 15 wt%. of LiClO4 doped PVA/MAA:EA polymer blend films.


458

T. Siddaiah et al. / Journal of Science: Advanced Materials and Devices 3 (2018) 456e463

hydrogen bonds formed between PVA and MAA: EA. The peak at
2q ¼ 19.5 has been found to increase in broadness and decrease in
intensity as Liþ ion content increases and enhances the complexation between the polymer blend and LiClO4 [17].
Hodge et al. [18] established a relationship between the peak
intensity and degree of crystallinity. They observed that the intensity of the diffraction pattern decreases as the amorphous nature increases by the addition of a dopant. In the present work, no
sharp peaks were observed for higher concentrations of LiClO4 salt
in the polymer, which indicates the dominant presence of the
amorphous phase [19]. This amorphous nature leads to greater
ionic diffusion and high ionic conductivity, which can be observed
in amorphous polymers having a flexible main chain [20].
3.2. Ultraviolet and visible analysis
The optical absorption study can be used to gain the detailed
information about the band structure of solid materials. In optical
absorption phenomena, an electron is excited to a higher energy

state from a lower energy state by the absorption of a photon of
sufficient energy in the transmitting radiation. The electronic
transitions can be estimated from the changes in the transmitted
radiation. The optical absorption coefficient (a) can be evaluated
from the absorbance by the following relation [21].

Absorption coefficientðaÞ ¼ 2:303 Â

A
d

(1)

Fig. 2. The plot of (ahy)2 vs. (hy) of (a) pure (50:50) and different concentrations (b)
5 wt%, (c) 10 wt% and (d) 15 wt% of LiClO4 doped PVA/MAA:EA polymer blend electrolyte films.

where A is the absorbance and d is the thickness of the films.
The absorption coefficient (a) can be useful to determine the
optical energy band gap (Eg), which is an important parameter of
both organic and inorganic materials. The optical energy band gap
of the prepared films was estimated by using Tauc's relationship
[22],

À
Án
ðahyÞ ¼ B hy À Eg

(2)

where B is a factor that depends on the electronic transition

probability, which can be treated as the constant within the optical
frequency range and the index n represents the type of electronic
transition, which related to the distribution of the density of the
states. For direct electronic transitions, n takes the values of 1/2 or
3/2 and for indirect transitions n is equal to 2 or 3, depending on
whether they are allowed or forbidden, respectively.
When the direct and indirect band gap exist, the absorption
coefficient has the following dependence on the energy of the
incident photon,



ahy¼ B1 hy À Egd
À

ahy¼ B2 hy À Egi

1=2

Á2

(3)
(4)

where Egd and Egi are the direct and indirect band gaps, respectively, B1 and B2 are constants.
Figs. 2 and 3 represent the plots of (ahy)2 and (ahy)1/2 versus
photon energy (hy) for pure and different weight fractions (5, 10
and 15 wt%) of LiClO4 doped PVA/MAA:EA polymer blend electrolyte films. The direct and indirect band gap values are determined
by extrapolating the linear part of the curves (ahy)2 and (ahy)1/2
versus photon energy (hy) to zero absorption value. The evaluated

band gap values (both direct and indirect) are reported in Table 1.
From Table 1, it is clear that both direct and indirect energy band
gap values decrease with increasing in the LiClO4 content in the
polymer blend. The doped LiClO4 salt increases the disorder of the

Fig. 3. The plot of (ahy)1/2 vs. (hy) of (a) pure (50:50) and different concentrations (b)
5 wt%, (c) 10 wt% and (d) 15 wt% of LiClO4 doped PVA/MAA:EA polymer blend electrolyte films.

polymer structure, which results in decreases in the optical band
gap value. Among all the prepared samples, the 15 wt% LiClO4
doped polymer blend electrolyte shows the minimum direct energy band gap and indirect energy band gap value. Hence it has
more semiconducting nature than remaining PVA complexed
polymer blend electrolyte films [23].
3.3. Fourier transform infrared analysis
Infrared spectroscopy has been used to identify interactions in
the polymer blends. FTIR spectroscopy is very sensitive to the


T. Siddaiah et al. / Journal of Science: Advanced Materials and Devices 3 (2018) 456e463

459

Table 1
Direct band and indirect band gap values for pure and LiClO4 doped PVA/MAA:EA (50:50) polymer blend electrolyte films.
PVA/MAA:EA: LiClO4 (wt%) sample composition

Direct band gap (eV)

Indirect band gap (eV)

50: 50: 0
47.5: 47.5: 5
45: 45: 10
42.5: 42.5: 15

5.04
4.90
4.68
4.04

4.36
3.91
3.82
3.66

formation of hydrogen bonds [24]. Fig. 4(aed) shows FTIR transmittance spectra of PVA/MAA:EA (50:50) blend without and with
different concentrations 5, 10 and 15 wt % of LiClO4 recorded at
room temperature in the region 500e4000 cmÀ1. FTIR transmittance band positions and their corresponding assignments are
presented in Table 2 for all prepared composite films.
Fig. 4(a) shows the FTIR spectrum of pure PVA/MAA:EA blend.
The bands at about 3135e3531 and 1436 cmÀ1 belong to the
stretching and bending vibration of the hydroxyl group, respectively [25]. The band characterized for the methylene group (CH2)
asymmetric stretching vibration occurs at about 2934 cmÀ1. The
band at about 1099 cmÀ1 corresponds to C e O stretching of acetyl
groups present on the PVA backbone [16,26]. The vibrational band
at about 1722 cmÀ1 is assigned to C ¼ O stretching of PVA and
MAA:EA copolymer.
The FTIR spectra of 5, 10 and 15 wt% of Lithium Perchlorate doped
films indicate a clear decrease in the intensity of the bands. From
Fig. 4, the following changes in the spectral features have been

observed for the PVA/MAA:EA (50:50) blend without and with
different concentrations of 5, 10 and 15 wt% of LiClO4. A broad and
very strong band observed at 3085e3539, 3135e3522 and
3119e3565 cmÀ1 for 5, 10 and 15 wt% of LiClO4 complexed films,
respectively, arises from O e H stretching frequency and is an indication of the presence of hydroxyl groups [24]. With increasing
dopant concentration the width increases and intensity of these
bands is found to decrease compared to the pure PVA/MAA:EA blend.
The vibrational peaks observed at 1099 and 1436 cmÀ1 for pure
blend are found to be absent in Liþ ion doped blend films. The
disappearance of bands observed in blend film with Liþ ion doping
suggests the co-ordination or complexation of chlorine with the
blend film [27].

Fig. 4. FTIR spectra of (a) pure (50:50) and different concentrations (b) 5 wt%, (c) 10 wt%
and (d) 15 wt% of LiClO4 doped PVA/MAA:EA polymer blend electrolyte films.

It was found that a small absorption band around 922 cmÀ1 is
characteristic of the syndiotactic structure of the prepared samples.
Syndioactivity of PVA/MAA: EA samples induces dense molecular
packing in a crystal, as well as stronger intermolecular hydrogen
bonds, which in turn, are responsible for the disappearance of
molecular motion [28]. This band appeared in the spectra of pure
blend film, but it disappeared in the spectra of the Liþ ion doped
blend and this may be attributed to the addition of Lithium.

3.4. Thermogravimetric analysis
Thermal stability and degradability of the prepared samples
were evaluated by thermogravimetric analysis [29]. Moreover, the
kinetics of the accompanied decomposition relation has been
reviewed. The sample weight decreases slowly as the reaction begins, then decreases rapidly over a comparatively narrow temperature range and finally levels off as the reactants are used up. The

shape of the curve depends primarily upon the kinetic parameters
involved, i.e., order of reaction (n), and activation energy (E). The
values of these parameters are important in the estimation of
thermal stability. TGA is used for studying the samples in the
temperature range of 30e600  C. Based on the TGA curves all the
films have shown three stages of weight loss. It is evident that the
initial weight loss for the pure PVA/MAA:EA blend sample starts
from 30 to 130  C with a weight loss of 7.8%, which may be due to
the loss of entrapped water molecules and moisture. The second
weight loss occurs at 131e390  C, which is attributed to melting
temperature (Tm), it is around 344  C. This weight loss is attributed
to the degradation of the unsaturated groups of PVA. The third
weight loss starts from 391 to 472  C with a weight loss of 21%.
Fig. 5 shows the dTGA curves of pure PVA/MAA:EA (50:50)
blend and PVA/MAA:EA blend filled with various weight fractions
of LiClO4 filler. As shown in Fig. 5(bed), all the doped films show
three stages of degradation. The initial weight loss for all the doped
samples starts from 30 to 150  C with the weight loss of 7e9%,
which may be due to the evaporation of the residual solvent,
moisture and impurities due to Chlorine compound (LiClO4).
Beyond the first stage, the samples have a drastic weight loss in the
temperature range 151e380  C with the weight loss of 30e60%,
which is assigned to melting temperature (Tm). The melting temperature of all the LiClO4 doped films exhibits decreasing nature as
LiClO4 content increases in the polymer matrix. This result in the
increase in the amorphous nature of the polymer blend electrolyte
films. The melting temperatures and decomposition temperatures
of pure and LiClO4 doped polymer blend electrolyte films are presented in Table 3. The second weight loss is ascribed to dehydrochlorination of LiClO4 which leads to the volatilization of
monomers and oligomers. The degradation of MAA:EA and the
elimination of the unsaturated functional group of PVA are the
contributions for final weight loss, which starts from 381 to 470  C.

In conclusion, among all the LiClO4 complexed polymer blend
electrolyte films, 15 wt% of LiClO4 doped film shows more amorphous nature than 5 and 10 wt%.
The activation energy (E) for the main thermal decomposition
for TGA measurements of the present samples, which depend on


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T. Siddaiah et al. / Journal of Science: Advanced Materials and Devices 3 (2018) 456e463

Table 2
Assignments of the FTIR characterization bands of pure and LiClO4 doped PVA/MAA:EA polymer blend electrolyte films.
PVA/MAA:EA: LiClO4 sample

Pure PVA/MAA:EA (50:50)
Wavenumber (cmÀ1)

Assignment

Wavenumber (cmÀ1)

Assignment

847
922
1099
1436
1722
2934
3135e3531

CH2 rocking
C e O stretching
C e O stretching
O e H and C e H bending
C ¼ O stretching
CH2 Asymmetric stretching
O e H stretching of alcohols and phenols

839
922
1722
2925
3085e3565
e
e

C ¼ C stretching
C e O stretching
C ¼ O stretching
C e H stretching of methylene group
O e H stretching
e
e

determined from the slope of these lines using the following
equation

E ¼ 2:303R Â slope

(8)

Values of the apparent activation energy (E) of the samples are
noted in Table 4.
3.5. Scanning electron microscopy

Fig. 5. dTGA thermograms of (a) pure (50:50) and different concentrations (b) 5 wt%,
(c) 10 wt% and (d) 15 wt% of LiClO4 doped PVA/MAA:EA polymer blend electrolyte
films.

the residual mass, can be calculated in general using the integral
equation of Coats and Redfern [30].

%
$
#
"
Àlogð1 À aÞ
R
2RT
E
À
1
À
¼
log
log
E
2:304R
DE

T2

(5)

where T is the absolute temperature, E is the activation energy in J/
mol, R is the universal gas constant (8.3136 J/mol K) and a is the
fractional weight loss at that particular temperature is calculated as

a¼

wi À wt
wi À wf

(6)

where wi is the initial weight, wt is the weight at a given temperature and wf is the final weight of the sample. For n ¼ 1, Eq. (1)
reduce to

%
$
#
"
Àlogð1 À aÞ
R
2RT
E
À 0:434
1À
¼ log
log

2
E
RT
DE
T

(7)

By plotting log½Àlogð1 À aÞ=T 2 Š against 1000/T for each sample,
we obtain straight lines. Then, the apparent activation energies are

A scanning electron microscope creates images of a sample by
scanning it with a focused electron beam. An electron beam interacts with electrons in a sample that generates various signals
that can be detected, and that contains information about the
morphology and composition of the sample surface. The electrons
in the beam interact with the sample, producing various signals
that can be used to obtain information about the surface topography, morphology and composition that makes it invaluable in a
variety of science and industry applications [31].
SEM is also used to study compatibility between different
components of polymer electrolytes by detecting phase separations
and interfaces [32,33]. Compatibility between the polymer mixture
and inorganic additives has a great influence on the thermal, mechanical and ionic properties of polymer electrolytes.
Fig. 6 shows the SEM images of pure PVA, Pure MAA:EA and
PVA/MAA:EA (50:50) blend without and with different concentrations 5, 10 and 15 wt% of Lithium Perchlorate. It can be seen from
Fig. 6(a) that pure MAA:EA copolymer film shows the smooth
surface, suggesting that MAA and EA molecules may disperse in the
soft e segment phase with little influence on the microphase
separation and mixing of the hard and soft segments [34]. The SEM
image of pure PVA film has no characteristics attributable to any
crystalline morphology. Hence the semicrystallinity of PVA discussed earlier is likely to be submicroscopic in nature [35].

Fig. 6(c) shows the SEM images of PVA/MAA:EA (50:50) polymer
blend electrolyte. The lateral branches correlate poorly with the
length of the trunk of the dendrites. The growth of a dendrite-like
form, which is a collection of branched aggregate clusters has
begun and lead to the formation of a condensed aggregated form of
dendrites. This suggests the presence of structural reorganizations
of polymer chains [36]. Fig. 6(def) shows the SEM images of
different concentrations (5, 10 and 15 wt%) of LiClO4 doped polymer
blend films. The morphology was uniform with different degrees of
roughness. The increase in the degrees of roughness with increased

Table 3
Melting and decomposition temperatures of pure PVA/MAA:EA and PVA/MAA:EA: LiClO4 composite polymer blend electrolyte films.
PVA/MAA:EA: LiClO4 (wt%) Sample

Melting temperature (Tm) ( C)

Decomposition temperature (Td) ( C)

50:50:0
47.5:47.5:5
45:45:10
42.5:42.5:15

344
317
311
292

424

418
413
410


T. Siddaiah et al. / Journal of Science: Advanced Materials and Devices 3 (2018) 456e463

461

Table 4
Activation energy of pure PVA/MAA:EA and PVA/MAA:EA: LiClO4 Composite polymer blend electrolyte films.
PVA/MAA:EA: LiClO4 (wt%) Sample

Activation energy (E) (KJ/mol)

Activation energy (E) (eV)

50:50:0
47.5:47.5:5
45:45:10
42.5:42.5:15

88.45
84.23
82.78
77.34

1.46
1.39
1.37

1.28

Fig. 6. SEM images of (a) pure MAA:EA, (b) pure PVA, (c) pure (50:50) and different concentrations (d) 5 wt%, (e) 10 wt% and (f) 15 wt% of LiClO4 doped PVA/MAA:EA polymer blend
electrolyte films.

Liþ ion concentration indicates that the crystalline salt was broken
into small pieces and mixed into the polymer blend [11]. The SEM of
the blend film filled with 5 wt% LiClO4 depicts a small spherulite
shape, scattered and distributed randomly in an isolated form
throughout the film. With an increase in the concentration of the
filler upto 10 wt%, the number of the spherulites considerably increases. This leads to the increase in the degree of roughness and
indicates the segregation of dopant in the host matrix. As the
dopant concentration increases, the size of the spherulites increases leading to the formation of isolated spherulites distributed
all over the volume of the film [37].

electrode/electrode interface [39]. This offers an increasing
impedance against the ion transfer with decreasing the frequency.
The linear region in the low-frequencies is due to the influence

3.6. Electrical conductivity
The ionic conductivity of the polymer electrolytes mainly depends on the actual concentration of conducting charge carriers
and their mobility. Fig. 7 shows the typical impedance plots of
(PVA/MAA:EA) polymer electrolyte doped with various concentrations of LiClO4 at ambient temperature in the frequency range of
1 Hze5 MHz. From Fig. 7, one observed a semicircle in the highfrequency region and a tilted straight line in the low-frequency
region. The presence of a semicircle indicates the non-Debye
character of the sample [38], since the potential well of each site
through which the ion transfer takes place is not equal. It is
widely accepted that the semicircle is due to the bulk resistance and capacitance of the electric double layer formed at the

Fig. 7. Impedance plots (Cole-Cole plots) for (a) pure (50:50) and different concentrations (b) 5 wt%, (c) 10 wt% and (d) 15 wt% of LiClO4 doped PVA/MAA:EA polymer

blend electrolyte films.


462

T. Siddaiah et al. / Journal of Science: Advanced Materials and Devices 3 (2018) 456e463

of blocking electrodes. With a higher concentration of dopant, the
lines slightly approach the imaginary axis, which indicates the
establishment of a better contact with the electrode. The ionic
conductivity of the solid polymer blend electrolytes was
calculated using the following equation.

s ¼ t=Rb A

(9)

where t is the thickness of the polymer blend electrolyte, A is the
area of the blocking electrode and Rb is the bulk resistance of
polymer blend electrolyte. It is evident from the cole-cole plots at
different dopant concentrations that the intercept of the semicircle
(bulk resistance) on the real axis tends towards lower values with
increasing the dopant concentration which indicates that the
conductivity increases with dopant concentration.
Fig. 8 shows the conductivity values of PVA/MAA:EA þ LiClO4
complexes as a function of salt concentrations at ambient temperature in the frequency range of 1 Hze5 MHz. From Fig. 8, it is

Fig. 8. Conductivity vs. salt concentration plots of (PVA/MAA:EA þ LiClO4) polymer
blend electrolyte system at room temperature.

Fig. 9. Frequency dependent conductivity at room temperature for (a) pure (50:50)
and different concentrations (b) 5 wt%, (c) 10 wt% and (d) 15 wt% of LiClO4 doped PVA/
MAA:EA polymer blend electrolyte films.

Table 5
The conductivity values of Pure and LiClO4 doped (PVA/MAA:EA) Polymer blend
electrolyte films at room temperature.
PVA/MAA:EA: LiClO4 sample composition (wt%)

Conductivity at 303 K (S/cm)

50.0:
47.5:
45.0:
42.5:

2.46
3.86
4.39
7.35

50.0:
47.5:
45.0:
42.5:

0
5
10
15

Â
Â
Â
Â

10À8
10À8
10À8
10À8

observed that the ionic conductivity increases with increasing
LiClO4 content in the polymer blend electrolyte. The maximum
conductivity of 7.35 Â 10À8 S/cm was obtained for the PVA/
MAA:EA þ LiClO4 (42.5:42.5:15) system. The conductivity values of
different complexes at room temperature are summarized in
Table 5. The highest ionic conductivity at 15 wt% salt doping is
attributed to the highest electrolyte uptake. Notes that, the conductivity is related to the number of Liþ ion charge carriers (ni) and
their mobility (mi) [40]. The coordination interaction of oxygen
atoms of MAA:EA with Liþ cations of LiClO4 salt results in an increase in mobile charge carriers and reduction in the crystallinity of
the PVA/MAA:EA mixture. This is responsible for the increase of
ionic conductivity. These interactions have also been observed by
FTIR, XRD and SEM analysis.
Fig. 9 shows the plots of the logarithm of conductivity as a
function of the logarithm of frequency for all the samples at room
temperature. The spectrum consists of two distinguishable regions
within the measured frequency range. The low-frequency region
describing electrode-electrode interfacial phenomena is ascribed to
the space charge polarization at the blocking electrodes [41]. The
high-frequency region corresponding to the bulk relaxation phenomena disappears gradually for the electrolytes, having the salt

concentration up to 15 wt% may be due to the increase in jump
frequency of charge carriers. The conductivity of polymer electrolytes initially increases due to the increment of charge carriers
being introduced into the complex. As the salt concentration increases, the number of carrier ions of the complex increases upto a
particular limit of the salt concentration. Above this concentration
there is a stronger ion-ion interaction which possibly prevents the
polymer backbone's segmental motion and then causes a lowering
of the dc conductivity [42].
4. Conclusion
The pure polymer blend (50PVA:50MAA:EA) electrolyte and
Polymer blend (50PVA:50MAA:EA) electrolytes with different
concentrations (5, 10 and 15 wt%) of LiClO4 have been prepared by
the solution casting technique using the double distilled water. Xray diffraction patterns show a decrease in the degree of crystallization and cause an increase in the amorphous region. The FTIR
spectra show the position shifts as well as the intensity changes.
This indicates the considerable interaction between the polymer
blend and LiClO4. The dTGA curve shows three different stages of
weight loss, which are due to the loss of the adsorbed water, the
decomposition of the side chain and the main chain. The melting
and decomposition temperatures exhibit a decreasing trend with
increasing LiClO4 content in the polymer blend, which indicates the
increase in amorphous nature. SEM images of the Liþ ion doped
films revealed the presence of the structural rearrangement of
polymer chains. UV e Visible analysis revealed that the value of the
optical band gap decreases as the LiClO4 content increases in the
polymer blend. This indicates the formation of charge transfer
complexes between the polymer blend and the filler. The
maximum conductivity of 7.35 Â 10À8 S/cm was obtained for the
system PVA/MAA:EA þ LiClO4 (42.5:42.5:15) at room temperature.


T. Siddaiah et al. / Journal of Science: Advanced Materials and Devices 3 (2018) 456e463

From all the characterization results, the 15 wt% of LiClO4 doped
polymer blend electrolyte system exhibits the better semiconducting nature which is more suitable for fabricating solid-state
batteries and other electrochemical devices.

[21]

Acknowledgments

[22]

The authors thank E. Bhoje Gowd, Senior Scientist, Department
of Materials and Minerals, National Institute of Interdisciplinary
Science and Technology (NIIST), Thiruvanthapuram, Kerala, for his
constant encouragement and active cooperation to carry out the
work.

[20]

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