MAA:EA polymer blendfilled with different concentrations of Lithium Perchlorate

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

a r t i c l e i n f o

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

Polymer

Lithium Perchlorate
PVA/MAA:EA blend
FTIR

TGA
Xe ray

SEM and optical energy

a b s t r a c t

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 2q¼ 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. UVe 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 thefiller. 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
LiClO4filled PVA/MAA:EA, FTIR spectra showed disappearance of some bands with the change in their

intensities as compared to pure PVA/MAA:EAfilm. This indicated considerable interaction between the
polymer blend and LiClO4filler. SEM images of the polymer blend films complexed with LiClO4suggested

the presence of a structural rearrangement of the polymer chains. The electrical conductivity of the
preparedfilms 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 Liỵion
concentration.

â 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 ( />

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]. Liỵion 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].

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 af_{finity with the liquid electrolyte and the}
other showing proper mechanical properties are used. The most
used polymer blend electrolytes are (PVAe PANI), (PVA e PAN),
(PVPe 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),
(Chitosane PVA), (PVA e NyC), (PEMA e PVdF), (PVA e NaAlg) and
its copolymers P(VDFe 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

* Corresponding author.

E-mail address:(Ch. Ramu).

Peer review under responsibility of Vietnam National University, Hanoi.

Contents lists available atScienceDirect

Journal of Science: Advanced Materials and Devices

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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
micro-phase configuration can induce drastic changes in all the
proper-ties (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
prep-arations, recycling of polymers, packaging textiles and leather
in-dustries 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
ad-vantages 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
compo-sition 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 Liỵto
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].

2. Experimental

MAA: EA copolymer (1:1) dispersion of 30 percent is a
disper-sion 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

m

m) pure PVA/
MAA:EA and different compositions of LiClO4complexedfilms 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 LiClO4were 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 dopedfilms at the bottom
of the dishes. The thermal properties of the prepared samples were
studied using SEIKO thermal analysis system (TGAe 20) in the
presence of nitrogenflow from 40 to 700_{C, at the heating rate of}
10C/min. The X-ray diffraction patterns were performed using a
Siemens D5000 diffractometer with CuK

a

radiation (

l

¼ 1.5406 Å).
The preparedfilms were scanned at 2

q

angles with a step size of

0.02 between 0 and 40. FTIR spectra of the prepared samples
were recorded using a PerkineElmer FTIR spectrometer, over a
wavenumber range 500e4000 cm1. SEM images of the polymer
blend electrolytefilms were characterized by Hitachi (TM e 3000
and He 8100) electron microscope with scanning attachment. The
optical absorption curves of thefilms 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 electrolytefilms 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,
thinfilms, nanomaterials and solid objects.Fig. 1shows 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 2

q

¼ 19.5_{, 1.4}_{and 0.6}_{, which}
in-dicates the semi-crystalline nature of the PVA/MAA:EA polymer
blendfilm[14]. Thefirst one has a clear crystalline peak at a
scat-tering angle 2

q

¼ 19.5_{which corresponds to a (1 1 0) re}_flection

[15]. The present X-ray pattern revealed no significant changes in
the positions of three peaks after complexation withfiller, the
in-tensity 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 Liỵcontent
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

elec-trolyte systems. The decrease in crystallinity with increasing LiClO4
content in the blended sample involves a decrease in the number of

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hydrogen bonds formed between PVA and MAA: EA. The peak at
2

q

¼ 19.5_{has been found to increase in broadness and decrease in}
intensity as Liỵion content increases and enhances the
complex-ation 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
in-tensity of the diffraction pattern decreases as the amorphous
na-ture increases by the addition of a dopant. In the present work, no
sharp peaks were observed for higher concentrations of LiClO4salt
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 aflexible 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 coefficient

a

ị ẳ 2:303 A

d (1)

where A is the absorbance and d is the thickness of thefilms.
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 preparedfilms was estimated by using Tauc's relationship

[22],

ð

a

h

y

Þ ¼ B h

y

 Eg

n

(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,

a

h

y

¼ B1



h

y

 Egd

1=2

(3)

a

h

y

¼ B2 h

y

 Egi

2

(4)
where Egdand Egiare the direct and indirect band gaps,
respec-tively, B1and B2are constants.

Figs. 2 and 3represent the plots of (

a

h

y

)2_{and (}

_a

_h

_y

₎1/2_versus
photon energy (h

y

) for pure and different weight fractions (5, 10
and 15 wt%) of LiClO4doped PVA/MAA:EA polymer blend
electro-lytefilms. The direct and indirect band gap values are determined
by extrapolating the linear part of the curves (

a

h

y

)2and (

a

h

y

)1/2
versus photon energy (h

y

) to zero absorption value. The evaluated
band gap values (both direct and indirect) are reported inTable 1.
FromTable 1, it is clear that both direct and indirect energy band
gap values decrease with increasing in the LiClO4content in the
polymer blend. The doped LiClO4salt increases the disorder of the

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
en-ergy band gap and indirect enen-ergy band gap value. Hence it has
more semiconducting nature than remaining PVA complexed
polymer blend electrolytefilms[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

Fig. 2. The plot of (ahy)2_{vs. (h}_y_{) of (a) pure (50:50) and different concentrations (b)}

5 wt%, (c) 10 wt% and (d) 15 wt% of LiClO4doped PVA/MAA:EA polymer blend

elec-trolytefilms.

Fig. 3. The plot of (ahy)1/2_{vs. (h}_y_{) of (a) pure (50:50) and different concentrations (b)}

5 wt%, (c) 10 wt% and (d) 15 wt% of LiClO4doped PVA/MAA:EA polymer blend

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formation of hydrogen bonds[24].Fig. 4(aed) shows FTIR
trans-mittance spectra of PVA/MAA:EA (50:50) blend without and with
different concentrations 5, 10 and 15 wt % of LiClO4recorded at
room temperature in the region 500e4000 cm1. FTIR
trans-mittance band positions and their corresponding assignments are
presented inTable 2for all prepared compositefilms.

Fig. 4(a) shows the FTIR spectrum of pure PVA/MAA:EA blend.
The bands at about 3135_{e3531 and 1436 cm}1 belong to the
stretching and bending vibration of the hydroxyl group,
respec-tively[25]. The band characterized for the methylene group (CH2)
asymmetric stretching vibration occurs at about 2934 cm1. The
band at about 1099 cm1corresponds to Ce O stretching of acetyl
groups present on the PVA backbone[16,26]. The vibrational band

at about 1722 cm1is assigned to C¼ 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 3085_{e3539, 3135e3522 and}
3119e3565 cm1_{for 5, 10 and 15 wt% of LiClO}₄_complexed_films,
respectively, arises from Oe H stretching frequency and is an
indi-cation 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 cm1for pure
blend are found to be absent in Liỵ ion doped blend lms. The
disappearance of bands observed in blendlm with Liỵ_{ion doping}
suggests the co-ordination or complexation of chlorine with the
blendfilm[27].

It was found that a small absorption band around 922 cm1is
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
blendfilm, but it disappeared in the spectra of the Liỵion 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
be-gins, then decreases rapidly over a comparatively narrow
temper-ature 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 130C 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 344C. This weight loss is attributed
to the degradation of the unsaturated groups of PVA. The third
weight loss starts from 391 to 472C with a weight loss of 21%.

Fig. 5 shows the dTGA curves of pure PVA/MAA:EA (50:50)
blend and PVA/MAA:EA blendfilled with various weight fractions
of LiClO4filler. As shown inFig. 5(bed), all the doped films show
three stages of degradation. The initial weight loss for all the doped
samples starts from 30 to 150C 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 thefirst stage, the samples have a drastic weight loss in the

temperature range 151e380_{C with the weight loss of 30}_e60%,
which is assigned to melting temperature (Tm). The melting
tem-perature of all the LiClO4dopedfilms exhibits decreasing nature as
LiClO4content 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 LiClO4doped polymer blend electrolytefilms are
pre-sented inTable 3. The second weight loss is ascribed to
dehydro-chlorination 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 forfinal weight loss, which starts from 381 to 470_C.
In conclusion, among all the LiClO4 complexed polymer blend
electrolytefilms, 15 wt% of LiClO4dopedfilm shows more
amor-phous 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

Table 1

Direct band and indirect band gap values for pure and LiClO4doped PVA/MAA:EA (50:50) polymer blend electrolytefilms.

PVA/MAA:EA: LiClO4(wt%) sample composition Direct band gap (eV) Indirect band gap (eV)

50: 50: 0 5.04 4.36

47.5: 47.5: 5 4.90 3.91

45: 45: 10 4.68 3.82

42.5: 42.5: 15 4.04 3.66

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

log


log1 

a

ị
T2



ẳ log

_D

R_E


12RT_E


_2:304RE (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

a

¼wi wt

wi wf

(6)
where wiis the initial weight, wtis the weight at a given
temper-ature and wfis thefinal weight of the sample. For n ẳ 1, Eq.(1)
reduce to

log


log1 

a

ị
T2


ẳ log

_D

R

E


12RT
E



 0:434 E

RT (7)

By plotting logẵlog1 

a

ị=T2_{ against 1000/T for each sample,}
we obtain straight lines. Then, the apparent activation energies are

determined from the slope of these lines using the following

equation

E¼ 2:303R  slope (8)

Values of the apparent activation energy (E) of the samples are
noted inTable 4.

3.5. Scanning electron microscopy

A scanning electron microscope creates images of a sample by
scanning it with a focused electron beam. An electron beam
in-teracts 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
topog-raphy, 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,
me-chanical and ionic properties of polymer electrolytes.

Fig. 6shows the SEM images of pure PVA, Pure MAA:EA and
PVA/MAA:EA (50:50) blend without and with different
concen-trations 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 PVAfilm has no characteristics attributable to any
crystalline morphology. Hence the semicrystallinity of PVA
dis-cussed 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(d_{ef) shows the SEM images of}
different concentrations (5, 10 and 15 wt%) of LiClO4doped polymer
blendfilms. The morphology was uniform with different degrees of
roughness. The increase in the degrees of roughness with increased

Table 2

Assignments of the FTIR characterization bands of pure and LiClO4doped PVA/MAA:EA polymer blend electrolytefilms.

Pure PVA/MAA:EA (50:50) PVA/MAA:EA: LiClO4sample

Wavenumber (cm1) Assignment Wavenumber (cm1) Assignment

847 CH2rocking 839 C¼ C stretching

922 Ce O stretching 922 Ce O stretching

1099 Ce O stretching 1722 C¼ O stretching

1436 Oe H and C e H bending 2925 Ce H stretching of methylene group
1722 C¼ O stretching 3085e3565 Oe H stretching

2934 CH2Asymmetric stretching e e

3135e3531 Oe H stretching of alcohols and phenols e e

Fig. 5. dTGA thermograms of (a) pure (50:50) and different concentrations (b) 5 wt%,
(c) 10 wt% and (d) 15 wt% of LiClO4doped PVA/MAA:EA polymer blend electrolyte

films.

Table 3

Melting and decomposition temperatures of pure PVA/MAA:EA and PVA/MAA:EA: LiClO4composite polymer blend electrolytefilms.

PVA/MAA:EA: LiClO4(wt%) Sample Melting temperature (Tm) (C) Decomposition temperature (Td) (C)

50:50:0 344 424

47.5:47.5:5 317 418

45:45:10 311 413

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Liỵion 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% LiClO}4depicts a small spherulite
shape, scattered and distributed randomly in an isolated form

throughout thefilm. With an increase in the concentration of the
filler upto 10 wt%, the number of the spherulites considerably
in-creases. 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
in-creases leading to the formation of isolated spherulites distributed
all over the volume of thefilm[37].

3.6. Electrical conductivity

The ionic conductivity of the polymer electrolytes mainly
de-pends 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
concen-trations of LiClO4at ambient temperature in the frequency range of
1 Hze5 MHz. FromFig. 7, one observed a semicircle in the
high-frequency region and a tilted straight line in the low-high-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
resis-tance and capaciresis-tance of the electric double layer formed at the

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 in_fluence

Table 4

Activation energy of pure PVA/MAA:EA and PVA/MAA:EA: LiClO4Composite polymer blend electrolytefilms.

PVA/MAA:EA: LiClO4(wt%) Sample Activation energy (E) (KJ/mol) Activation energy (E) (eV)

50:50:0 88.45 1.46

47.5:47.5:5 84.23 1.39

45:45:10 82.78 1.37

42.5:42.5:15 77.34 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 LiClO4doped PVA/MAA:EA polymer blend

electrolytefilms.

Fig. 7. Impedance plots (Cole-Cole plots) for (a) pure (50:50) and different
concen-trations (b) 5 wt%, (c) 10 wt% and (d) 15 wt% of LiClO4doped PVA/MAA:EA polymer

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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=RbA (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. 8shows the conductivity values of PVA/MAA:EAỵ LiClO4
complexes as a function of salt concentrations at ambient
tem-perature in the frequency range of 1 Hze5 MHz. FromFig. 8, it is

observed that the ionic conductivity increases with increasing
LiClO4 content in the polymer blend electrolyte. The maximum
conductivity of 7.35  108 _{S/cm was obtained for the PVA/}
MAA:EAỵ 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
con-ductivity is related to the number of Liỵion charge carriers (ni) and
their mobility (

m

i) [40]. The coordination interaction of oxygen
atoms of MAA:EA with Liỵcations of LiClO4salt results in an
in-crease 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. 9shows 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
phe-nomena 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
electro-lytes initially increases due to the increment of charge carriers
being introduced into the complex. As the salt concentration
in-creases, 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 LiClO4have been prepared by
the solution casting technique using the double distilled water.
X-ray diffraction patterns show a decrease in the degree of
crystalli-zation 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 LiClO4content in the polymer blend, which indicates the
increase in amorphous nature. SEM images of the Liỵion doped
lms revealed the presence of the structural rearrangement of
polymer chains. UVe Visible analysis revealed that the value of the

optical band gap decreases as the LiClO4content increases in the
polymer blend. This indicates the formation of charge transfer
complexes between the polymer blend and the filler. The
maximum conductivity of 7.35 108_{S/cm was obtained for the}
system PVA/MAA:EAỵ LiClO4(42.5:42.5:15) at room temperature.

Fig. 8. Conductivity vs. salt concentration plots of (PVA/MAA:EAỵ LiClO4) polymer

blend electrolyte system at room temperature.

Table 5

The conductivity values of Pure and LiClO4doped (PVA/MAA:EA) Polymer blend

electrolytefilms at room temperature.

PVA/MAA:EA: LiClO4sample composition (wt%) Conductivity at 303 K (S/cm)

50.0: 50.0: 0 2.46 108

47.5: 47.5: 5 3.86 108

45.0: 45.0: 10 4.39 108

42.5: 42.5: 15 7.35 108

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 LiClO4doped PVA/

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<span class='text_page_counter'>(8)</span><div class='page_container' data-page=8>

From all the characterization results, the 15 wt% of LiClO4doped

polymer blend electrolyte system exhibits the better
semi-conducting nature which is more suitable for fabricating solid-state
batteries and other electrochemical devices.

Acknowledgments

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.

References

[1] P. Harrop, H. Zervos, Batteries, Super Capacitors, Alternative Storage for
Portable Devices, 2010.

[2] J.K. Park, Principles and Applications of Lithium Secondary Batteries, Wiley,
2012.

[3] C.A. Vincent, Lithium batteries: a 50-year perspective, 1959-2009, Solid State
Ionics 134 (2000) 159e167.

[4] M. Yoshio, R.J. Brodd, A. Kozawa, Lithiume Ion Batteries: Science and
Tech-nologies, Springers, 2010.

[5] Jen-Taut Yeh, Peng Xu, Fang-Chang Tsai, Blending properties of poly(vinyl
alcohol) and nylon 6-clay nanocomposite blends, J. Mater. Sci. 42 (6) (2007)
6590e6599.

[6] D.R. Paul, S. Newman, Polymer Blends, Academic press, New York, 1978.
[7] Agil Abrahama, P.A. Solomanb, V.O. Rejini, Preparation of chitosan-polyvinyl

alcohol blends and studies on thermal and mechanical properties, Procedia
Technol. 24 (2016) 741e748.

[8] C. Umadevi, K.R. Mohan, V.B.S. Achari, A.K. Sharma, V.V.R.N. Rao, Discharge
characteristics of polymer blend (PVP/PVA) electrolytefilms doped with
po-tassium bromide, Ionics 16 (2010) 751e756.

[9] K.A.M. Abd El-Kader, S.F. Abdel Hamied, A.B. Mansour, A.M.Y. El-Lawindy, F. El
Tantaway, Material Properties Effect of the molecular weights on the optical
and mechanical properties of poly (vinyl alcohol)films, Polym. Test. 21 (7)
(2002) 847e850.

[10] J. Michalek, Sabina Abbrent, Michal Musil, Jana Kovarova, J. Hodan, Dybal,
New type of gel polymer electrolytes based on selected methacrylates and
their characteristics. Part II. Fluorinated Co-polymers, J. Electrochem. Acta 208
(2016) 211e224.

[11] V.M. Mohan, Weiliang Qiu, Jie Shen, Wen Chen, Electrical properties of
poly(vinyl alcohol) (PVA) based on LiFePO4 complex polymer electrolyte
films, J. Polym. Res. 17 (2010) 143e150.

[12] L.N. Sim, S.R. Majid, A.K. Arof, Characteristics of PEMA/PVdF-HFP blend
polymeric gelfilms incorporated with lithium triflate salt in electrochromic
device, Solid State Ionics 209e210 (2012) 15e23.

[13] D. Saikia, A. Kumar, Ionic conduction in P(VDF-HFP)/PVDFe(PC ỵ DEC)eLiClO4
polymer gel electrolytes, Electrochim. Acta 49 (16) (2004) 2581e2589.

[14] S.S. Liji Sobhana, J. Sundaraseelan, S. Sekar, T.P. Sastry, A.B. Mandal,

Gelati-neChitosan composite capped gold nanoparticles: a matrix for the growth of
hydroxyapatite, J. Nanoparticle Res. 11 (2) (2009) 333e340.

[15] A. Tawansi, A. El-Khodary, M.M. Abdelnaby, A study of the physical properties
of FeCl3filled PVA, Curr. Appl. Phys. 5 (6) (2005) 572e578.

[16] M. Abdelaziz, E.M. Abdelrazek, Effect of dopant mixture on structural, optical
and electron spin resonance properties of polyvinyl alcohol, Physica B 390
(1e2) (2007) 1e9.

[17] A.M. Abdelghany, M.S. Meikhail, N.A. Elsheshtawy, H.Y. Salah, Structural and
thermal stabilization correlation of PEO/PVA-AgCl polymer composites,
Mid-dle East J. Appl. Sci. 5 (2015) 1e6.

[18] R.M. Hodge, G.H. Edward, G.P. Simon, Water absorption and states of water in
semi crystalline poly(vinyl alcohol)films, Polymer 115 (1996) 1371e1376.
[19] V. Madhu Mohan, V. Raja, A.K. Sharma, V.V.R. Narasimha Rao, Ionic

conduc-tivity and discharge characteristics of solid-state battery based on novel

polymer electrolyte (PEOỵ NaBiF4), Mater. Chem. Phys. 94 (2e3) (2005)
177e181.

[20] A.A. Mohamad, N.S. Mohamad, M.Z.A. Yahya, R. Othman, S. Ramesh, Y. Alias,
A.K. Aroof, Solid State Ionics 156 (1e2) (2003) 171e177.

[21] H.M. Ragab, Spectroscopic investigations and electrical properties of PVA/PVP
blendfilled with different concentrations of nickel chloride, Physica B 406

(20) (2011) 3759e3767.

[22] K. Hareesh, G. Sanjeev, A.K. Pandey, V. Rao, Characterization of UV- irradiated
Lexan polycarbonatefilms, Iran. Polym. J. 22 (5) (2013) 341e349.

[23] T. Rajavardhana Rao, I. Omkaram, K. Veera Brahmam, Ch. Linga Raju, J. Mol.
Struct. 1036 (2013) 94e101.

[24] S. Rajendran, M. Sivakumar, R. Subadevi, Investigations on the effect of
various plasticizers in PVAePMMA solid polymer blend electrolytes, Mater.
Lett. 58 (5) (2004) 641e649.

[25] Xu Li, S.H. Goh, Y.H. Lai, A.T.A. Wee, Miscibility of carboxyl-containing
poly-siloxane/poly (vinylpyridine) blends, Polymer 41 (17) (2000) 6563e6571.
[26] C.M. Laot, E. Marand, H.T. Oyama, Spectroscopic characterization of molecular

inter diffusion at a poly(vinyl pyrrolidone)/vinyl ester interface, Polymer 40
(5) (1999) 1095e1108.

[27] M.Y.A. Rahman, A. Ahmad, T.K. Lee, Y. Farina, H.D. Dahlan, Effect of Ethylene
Carbonate (EC) plasticizer on poly (vinyl chloride)-liquid 50% epoxidised
natural rubber (LENR50) based polymer electrolyte, Mater. Sci. Appl. 2 (7)
(2011) 817e825.

[28] M. Nagura, S. Matsuzawa, K. Yamaura, H. Ishikawa, Tacticity dependence of
molecular motion in crystal of poly (vinyl alcohol), Polym. J. 14 (1) (1982)
69e72.

[29] P. Balaji Bhargav, V. Madhu Mohan, A.K. Sharma, V.V.R.N. Rao, Structural,
electrical and optical characterization of pure and doped poly (vinyl alcohol)

(PVA) polymer electrolytefilms, Int. J. Polym. Mater. Polym. Biomater. 56 (6)
(2007) 579e591.

[30] T.K. Kwei, The effect of hydrogen bonding on the glass transition
tempera-tures of polymer mixtempera-tures, J. Polym. Sci. C Polym. Lett. 22 (6) (1984) 307e313.
[31] K. Vijaya Babu, V. Veeraiah, Dielectric and impedance analysis of Li0.5La0.5
Ti(1-x)ZrxO3( x¼ 0.05 and 0.1) ceramics as improved electrolyte material for
lithium-ion batteries, Mater. Sci. Poland 34 (3) (2016) 605e616.

[32] S. Zhang, Jim Y. Lee, L. Hong, Visualization of particle distribution in composite
polymer electrolyte systems, J. Power Sources 126 (1e2) (2004) 125e133.
[33] P. Balaji Bhargav, V. Madhu Mohan, A.K. Sharma, V.V.R.N. Rao, Structural and

electrical studies of sodium iodide doped poly (vinyl alcohol) polymer
elec-trolytefilms for their application in electrochemical cells, Ionics 13 (3) (2007)
173e178.

[34] Y. Madhava Kumar, N.O. Gopal, Ch. Ramu, S. Babu, J.L. Rao, H. Nagabhushana,
S.C. Sharma, Structural, thermal and optical properties of Cu2ỵdoped
meth-acrylic acideethyl acrylate (MAA:EA) copolymer films, Bul. Mater. Sci. 40 (5)
(2017) 877e886.

[35] T. Siddaiah, Pravakar Ojha, N.O. Gopal, V. Ramesh Kumar, Ch. Ramu,
Struc-tural, optical and thermal characterizations of PVA/MAA:EA polyblendfilms,
Mater. Res. 21 (5) (2018).

[36] B.C. Okerberg, Herve Marand, Jack F. Douglas, Dendritic crystallization in thin
films of PEO/PMMA blends: a comparison to crystallization in small molecule
liquids, Polymer 49 (2) (2008) 579e587.

[37] A. Ele Khodary, Evolution of the optical, magnetic and morphological
prop-erties of PVAfilms filled with CuSO4, Physica B 405 (16) (2010) 3401e3408.
[38] S. Lanfredi, P.S. Saia, R. Lebullenger, Electric conductivity and relaxation in
fluoride, fluorophosphate and phosphate glasses: analysis by impedance
spectroscopy, Solid State Ionics 146 (3e4) (2002) 329e339.

[39] K.M. Kim, K.S. Ryu, S.G. Kang, S.H. Chang, I.J. Chung, The effect of silica addition
on the properties of poly((vinylidenefluoride)-co-hexafluoropropylene)-based
polymer electrolytes, Macromol. Chem. Phys. 202 (6) (2001) 866e872.
[40] K. KiranKumar, M. Ravi, Y. Pavani, S. Bhavani, A.K. Sharma, V.V.R. Narasimha

Rao, Investigations on PEO/PVP/NaBr complexed polymer blend electrolytes
for electrochemical cell applications, J. Membr. Sci. 454 (2014) 200e211.
[41] Takakazu Yamamoto, Minoru Inami, Takaki Kanabara, Preparation and

properties of polymer solid electrolytes using poly(vinyl alcohol) and
ther-mally resistive poly[arylene(1,3-imidazolidine-2,4,5-trione-1,3-diyl)] as
ma-trix polymers, Chem. Mater. 6 (1) (1994) 44e50.

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