Poly (3,4-ethylenedioxythiophene) γ-Fe2O3 polymer composite–super paramagnetic behavior and variable range hopping 1D conduction mechanism–synthesis and characterization

POLYMERS FOR ADVANCED TECHNOLOGIES

Polym. Adv. Technol. 2008; 19: 229–236

rscience.wiley.com) DOI: 10.1002/pat.1003
Published online 5 November 2007 in Wiley InterScience (www.inte
Poly (3,4-ethylenedioxythiophene) g-Fe2O3 polymer

composite–super paramagnetic behavior and

variable range hopping 1D conduction

mechanism–synthesis and characterization

Kuldeep Singh, Anil Ohlan, Parveen Saini and S. K. Dhawan*Polymeric & Soft Materials Section, National Physical Laboratory, New Delhi 110012, India

Received 7 March 2007; Revised 21 August 2007; Accepted 21 August 2007

*CorrespoSection, NE-mail: sk

The present paper reports the preparation of poly (3,4-ethylenedioxythiophene) (PEDOT) ferri-

magnetic conducting polymer composite by incorporation of ferrite particles in the polymer matrix

by emulsion polymerization. Synthesis of PEDOT–g-Fe2O3 composite was carried out by chemical

oxidative polymerization of EDOT with ferrite particles in the presence of dodecylbenzenesulfonic

acid (DBSA) that works as dopant as well as surfactant in aqueousmedium. The resulting conducting

composite possesses saturation magnetization (Ms) value of 20.56 emu/g with a conductivity of

0.4 ScmS1, which was determined by VSM and four probe technique, respectively. B-H curve reveals

that ferrimagnetic particles of g-Fe2O3 show super-paramagnetic behavior at room temperature

which was also observed in PEDOT–g-Fe2O3 composite. The resulting conducting ferrimagnetic

composite shows microwave absorption loss of 18.7–22.8 dB in the frequency range of 12.4–18GHz.

Thermogravimetric analysis of the composite revealed that the composite is thermally stable up to

230-C. The characterization of the PEDOT–g-Fe2O3 composite was carried out using XRD and FTIR

spectroscopy. Copyright # 2007 John Wiley & Sons, Ltd.

KEYWORDS: conducting polymers; micelles; composites; PEDOT; ferrimagnetic conducting composites

INTRODUCTION

In last few decades, organic polymers possessing p-conjugated

extended system, with low energy band gap, has attracted the

attention of most of the material scientists, engineers, and

technocrats due to their intrinsically conducting nature in

doped form. Among the conducting polymers, much atten-

tion has been paid to polypyrrole, polyaniline, polythiophene

and their derivatives. Only very few low band gap polymers

(Eg< 1.5 eV) with high conductivity are known. Poly(3,4-

ethylenedioxythiophene) (PEDOT), which is a derivative of

polythiophene, has a moderate band gap.1 Polymerization

of 3,4-ethylenedioxythiophene (EDOT) takes place via 2,5-

couplings so that polymerization yields a polymer with

fewer defects and thus possesses better properties compared

to its thiophene analogs; due to their unique structural

properties and reaction mechanism it can be easily synthe-

sized by both electrochemical and oxidative redoxmethod.2,3

PEDOT has high transparency in visible regime, excellent

environmental stability, low redox potential, good thermal

stability, and can be doped either n-type or p-type which

ndence to: S. K. Dhawan, Polymeric & Soft Materialsational Physical Laboratory, New Delhi 110012, [email protected]

shows moderately high conductivity.4,5 These features of

PEDOT could be exploited in various applications in

electronic devices such as electrode material in rechargeable

polymer batteries,6,7 antistatic coating,8,9 electro chromic

devices,10,11 organic light emitting diodes (OLEDs),12,13 EMI

shielding,14,15 polymeric solar cell.16,17 Polymerization of

EDOT can be carried out by various techniques like disper-

sion method, suspension method, and emulsion method.

EDOT is partially soluble in water so the rate of polymeri-

zation retarded that ultimately decreases the conductivity of

the PEDOT. To solve this problem, many research groups

had reported that conductivity of PEDOT could be improved

by adding suitable organic solvent having high dielectric

constant18 which induces a screening effect between the

positively charged EDOT and negatively charged counter

ion and thus reduces the columbic interaction between the

two and enhances the solubility and rate of polymerization.

To enhance the application of conducting polymer in the

field of EMI shielding, memory devices and radar absorbing

material (RAM material), monomer is polymerized in the

presence of ferrite particles, as ferrites are good absorber of

the electromagnetic radiations.19 In recent years, a lot of

research work has been carried out on ferromagnetic compo-

sites of polypyrrole and polyaniline incorporating ferrite parti-

cles in the polymer matrix by in situ or ex situ process which

Copyright # 2007 John Wiley & Sons, Ltd.

230 K. Singh et al.

possesses moderate magnetization and conductivity.20–31 But

no work is done on the poly(3,4-ethylenedioxythiophene)-

ferrite composites. In the present paper, we have synthesized

the PEDOT composite with nano crystalline iron oxide with

the help of the emulsion method in aqueous medium by

using chemical oxidative polymerization using ammonium

peroxydisulfate as an oxidizing agent and DBSA as a dopant

which also work as a surfactant. To overcome the insoluble

nature of EDOT in an aqueous medium, homogenization of

EDOT was carried out in dodecylbenzenesulfonic acid

(DBSA) and subsequently polymerization was carried out.

The resulting ferrimagnetic conducting composite possesses

good magnetization value with moderate conductivity,

which is confirmed by VSM and four probe technique.

EXPERIMENTAL

Materials used3,4-ethylenedioxythiophene (Bayer AG), ammonium per

sulfate (Merck), DBSA, isopropyl alcohol, FeCl3.6H2O

(Merck), FeCl.2.4.H2O (Merck), and aqueous ammonia

solution are the materials used.

Synthesis of the nano crystalline ferric oxideThe ferric oxide g-Fe2O3 was prepared through the con-

ventional precipitation oxidation method.32 A mixture of

ferric chloride FeCl3.6H2O and ferrous chloride FeCl2.4H2O

in amolar ratio of 2:1 was prepared and the resultingmixture

is precipitated by adding aqueous solution of ammonia drop

by drop with continuous vigorous stirring by maintaining

the pH of the solution up to 11–12. The reaction was stirred

for 3–5 hr at room temperature and brownish black pre-

cipitate was formed which was filtered and washed

thoroughly with distilled water. The resulting precipitate

was dried for 24 hr at 1208C. The formation of g-Fe2O3

particles was confirmed by XRD with a crystallite size of

9.17 nm and saturation magnetization (Ms) value was found

to be 69.0 emu/g.

Synthesis of the PEDOT–g-Fe2O3 composite viamicro emulsion oxidative polymerization inaqueous mediumThe synthesis of the PEDOT–g-Fe2O3 composite was carried

out by the micro emulsion polymerization method in

aqueous medium. First a micro-emulsion of g-Fe2O3 and

DBSA is prepared by homogenizing DBSA and g-Fe2O3 in

distilled water, with the homogenizer ART-Miccra D-8

(No-10956) at rpm of 10,500 for 50–60 min. A thick paste of

ferric oxide particles embedded in DBSAwas formed inwhich

an appropriate amount of 3,4-ethylenedioxythiophene, EDOT

(0.1M) was added and again homogenized for 2–3 hr

resulting in the formation of the micelles of EDOT with

g-Fe2O3. Themicelles, so formed, are polymerized below 08Cthrough chemical oxidization polymerization by using

ammonium per sulfate, (NH4)2S2O8 (0.1M). The mixture

was stirred for 12–15 hr during which the color of the

solution changes from brown to light blue and then finally to

dark green. The product obtained was demulsified using

equal amount of isopropyl alcohol and the product was

filtered and washed with alcohols and dried at 60–658C. A


similar synthesis was carried out for PEDOT–DBSA in the

absence of ferrite particles.

Structural characterizationThe conductivity of the powder pallet of the sample PEDOT–

g-Fe2O3 composite was measured by the four probe method

using Keithley programmable current source and nanovolt-

meter attached to digital temperature controller and APD

Cryo cooler. The magnetic measurements of the ferrite as

well as conducting composites were carried out using the

vibrating sample magnetometer (VSM), Model 7304, Lake-

shore Cryotronics Inc. USA. FTIRwas carried onNicolet 5700

and XRD studies were carried out on D8 Advance Bruker

AXS X-ray diffractometer from 2u¼ 108 to 708 at a scan rate of

0.0258/sec. Thermogravimetric analysis of the polymer and

composites was carried on a Mettler Toledo TGA 851e and

DSC measurement was recorded on DSC 855c. Shielding

measurements were carried out on an Agilent E8362B Vector

Network Analyzer in a microwave range of 12.4–18GHz

(P-band). Measurements were carried out using 15.8�7.9� 6mm3 copper sample holder connected between the

wave guide flanges of network analyzer. To avoid air gap

the above sample holder is modified with a grove of 1.5mm

on each side and 3mm deep.

RESULT AND DISCUSSION

MechanismA proper polymerization technique plays a vital role in

determining the morphology, molecular weight, chain

linearity, and internal defects in the properties of the

material. In the PEDOT–g-Fe2O3 composite formation in

the aqueous medium, water is the continuous phase and

DBSA as a surfactant acts as the discontinuous phase and the

monomer EDOT is emulsified along with the ferrite particles

to form micromicelles of oil-in-water type. Emulsion poly-

merization has high degree of polymerization than those

prepared by suspension and precipitation method. A typical

micelle in an aqueous solution forms a roughly spherical

or globular aggregate with the hydrophilic ‘‘head’’ regions

in contact with surrounding solvent, sequestering the

hydrophobic tail regions in the micelle center. The shape

of a micelle is a function of the molecular geometry of

its surfactant molecules and solution conditions such as

surfactant concentration, temperature, pH, and ionic

strength. Generally in micellar solution there are the chances

of formation of macroscopic particles that can be prevented

by adding the steric stabilizers like poly (vinyl alcohol),

poly (N-vinylpyrrolidone), and cellulose ethers, but in this

present system the bulky surfactant DBSA itself acts to

prevent the formation of the macroscopic precipitation.

When monomer EDOT is added to the DBSA micelle, it

occupies the place in between the micelle and surrounded by

the hydrophilic sulfonate unit and on addition of oxidants

like APS, the polymerization takes place at the interface

boundary. It has also been observed that the color of the

reaction mixture containing DBSA, EDOT, and ferric oxide

changes from dark brown to green before the addition of

oxidant. This color transformation may be due to the

formation of coordination bond between Fe–S of g-Fe2O3


DOI: 10.1002/pat

Scheme 1. Proposed mechanism for the polymerization of EDOT.

Scheme 2. Proposed coordination of PEDOT–g-Fe2O3

composite. This figure is available in colour online at www.

interscience.wiley.com/journal/pat

Poly (3,4-ethylenedioxythiophene) g-Fe2O3 polymer composite 231

and monomer EDOT which has a lone pair of electron and

may overlapwith the vacant d-orbital of the Fe. This was also

confirmed through FTIR.When the oxidative polymerization

of the micellar solution containing EDOT was carried out by

using the ammonium peroxodisulfate, the color of the

solution starts changing from green to blue and ultimately

to dark black green after the complete polymerization in

12–14 hr. Addition of the APS leads to the formation of

cationic free radicals, which combines with another mono-

mer moiety to form a dimer, which on further oxidation and

combination with another cation radical forms a termer and

ultimately to a long chain of polymer. The polymerization

of the EDOT is shown in Scheme 1 and the proposed

mechanism of coordination of PEDOT with ferric oxide

particles is shown in Scheme 2.

FTIR characterization of PEDOT andPEDOT–g-Fe2O3 compositeThe formation of the linkage between Fe S was further

investigated by the FTIR spectroscopy. Figure 1 shows the

FTIR spectra of pure g-Fe2O3, PEDOT–DBSA and PEDOT–

g-Fe2O3 composite. The vibrational bands at around

1322 cm�1 and 1519 cm�1 are due to C–C or C––C stretching

of quinoid structure of thiophene ring and due to ring

stretching of thiophene ring, respectively. Vibrational bands

at 1186 cm�1, 1139 cm�1, and 1080 cm�1 arise due to C–O–C

bond stretching in the ethylene dioxy group. C–S bond in the

thiophene ring is also seen at 975 cm�1, 834 cm�1, and


681 cm�1. These peaks are almost similar in both blank

PEDOT and PEDOT–g-Fe2O3 composite. FTIR spectra of the

g-Fe2O3 shows the Fe–O bond stretching at 557 cm�1 and

632 cm�1 respectively The presence of band at 557 cm�1 in

the composite clearly shows the presence of g-Fe2O3 in the

composite which was absent in the blank PEDOT–DBSA.

The absence of band at 632 cm�1 in the FTIR spectra of the

composite (Fig. 1, curve c) can be assigned to the formation of

linkage between Fe–S. Moreover there is a shift in the


DOI: 10.1002/pat

Figure 1. FTIR spectra of ferric oxide (a), PEDOT–DBSA (b),

and PEDOT–DBSA-ferric oxide composite (c).

232 K. Singh et al.

frequency from 681 cm�1 to 689 cm�1 which is observed due

to C–S bond stretching.

XRD studiesX-ray scattering pattern of the PEDOT–g-Fe2O3 composite

and iron oxide g-Fe2O3 is shown in Fig. 2. Themain peaks for

g-Fe2O3 are observed at 2u¼ 30.288 (d¼ 2.95 A), 35.708 (d¼2.51 A), 43.458 (d¼ 2.08 A), 53.808 (d¼ 1.70 A), 57.448 (d¼1.60 A), 63.058 (d¼ 1.47 A) corresponding to the (2 2 0), (3 1 1),

(4 0 0), (4 2 2), (5 1 1), (4 4 0) reflections33 which matches with

the standard XRD pattern of g-Fe2O3 (Powder Diffraction

File, JCPDS No. 39–1346). The peaks present in g-Fe2O3 were

also observed in the PEDOT–g-Fe2O3 composite which

indicates the presence of ferrite particles in the polymer

matrix. The XRD pattern of PEDOT is shown by the broad

peak at 2u¼ 24.738 (d¼ 3.60 A).34 The line broadening of the

peaks in the entire patterns of both g-Fe2O3 particles and

PEDOT–ferrite composite indicates the small dimensions of

the iron oxide particles. The crystallite size of g-Fe2O3

particle can be calculated by line broadening using Scherer’s

formula

D ¼ kl=b cos u

Figure 2. XRD data of ferric oxide (a), PEDOT–ferric oxide

composite (b) and PEDOT–DBSA (c). This figure is available

in colour online at www.interscience.wiley.com/journal/pat


where D is the crystallite size for individual peak of the

crystal in angstroms, l the X-ray wavelength, k the shape

factor, u the Bragg angle in degrees, and b is the line

broadening measured by half-height in radians. The value of

k is often assigned a value of 0.89, which depends on several

factors, including the Miller index of the reflecting plane and

the shape of the crystal. The size of g-Fe2O3 particles can be

calculated from the highest intensity peak35 and estimated as

9.17 nm for pure g-Fe2O3 and 10.64 nm for PEDOT–g-Fe2O3

composite. The unit cell parameters are also calculated for

g-Fe2O3 and PEDOT composite using Powder X software.

The powder X-ray pattern shows cubic structure with

a¼ 8.33 A for g-Fe2O3 and a¼ 8.34 A for PEDOT–g-Fe2O3

composite.

Thermal behavior of PEDOT andPEDOT–g-Fe2O3 compositeThe thermogravimetric analysis of conducting polymer

PEDOT was carried out in the presence and absence of

ferrite particles in order to see the effect of temperature on

the thermal behavior of the polymer. The thermogram of

PEDOT–DBSA (Fig. 3, curve a) shows that polymer is

thermally stable up to the 1828C. A weight loss of �3% is

observed up to 1108C which is most probably due to the loss

of water molecules entrapped in the polymer moiety. From

1828C to 3008C, the loss is 19.3%which can be accorded to the

dedoping of the dopant from the polymer matrix. But from

3008C to 7008C, there is a continuous loss of 40.8%, which

may be due to the degradation of the polymer backbone.

On comparing this thermogram with the thermal behavior

of the composite (Fig. 3, curve b) the thermal stability of the

composite has been found to increase up to 2308C. Initialweight loss of 4.6% is observed up to 1108C which may be

due to the loss of water molecules entrapped in the polymer

matrix. From 2308C to 3008C, weight loss observed is 3.7%

which is accounted due to the partial leaching of the dopant

from the polymer composite matrix. Aweight loss of 30.2% is

observed from 300 to 7008C, which is accounted due to the

degradation of the polymer backbone and the total weight

Figure 3. TGA data of PEDOT (curve a), PEDOT–ferric

oxide composite (curve b) at a scan rate of 108C/min

under N2. This figure is available in colour online at www.

interscience.wiley.com/journal/pat


DOI: 10.1002/pat


loss of 41.3% has been observed up to 7008C. This

enhancement in the thermal stability can be accounted due

to some ionic interaction of the g-Fe2O3 with sulfur atom of

the thiophene ring which may form a coordinate bond

between Fe–S as Fe has an incomplete d-orbital to which

sulfur can donate its lone pair of electrons that results in the

enhancement of the thermal stability of the resulting unit.

DSC behavior of PEDOT synthesized in DBSA medium

shows two peak transitions at 1108C and 2208C which may

correspond to the loss of water entrapped in the polymer

matrix and later to the transition taking place corresponding

to the dopant attached to polymeric backbone. This peak

cannot be accounted to be the true glass transition of the

PEDOT–DBSA. However, DSC behavior of the PEDOT–

g-Fe2O3 composite shows the endotherms at 1008C with a

doublet and second at 2808C which may be associated with

greater interaction of dopant–ferric oxide–polymer system.

Magnetic properties of the compositeMaghemite (g-Fe2O3) is a cubic spinel structure like (AB2O4)

with vacant B site and two distinct sub lattices (A and B in the

spinal structure) which give origin to ferrimagnetic ordering

in the compound. These nano crystalline g-Fe2O3 particles

show super paramagnetic (SPM) behavior at room tempera-

ture with Ms value of 69.0 emu/g (Fig. 4, curve a). When

these particles are incorporated in the polymer matrix

resulting in the formation of PEDOT–g-Fe2O3 composite, the

magnetization value was found to be 20.56 emu/g (Fig. 4,

curve b) while the SPM nature remains unaffected as the

coercivity (Hc¼ 4.93G) and retentivity (Mr¼�0.1196 emu/g)

remain almost same. From these results it is clear that the

PEDOT–g-Fe2O3 composite is ferrimagnetic in nature and

will work as a good absorber of the microwave in the

GHz range.

Conductivity measurementThe DC conductivity measurement has been carried out

using the compressed pallet of the PEDOT–g-Fe2O3 in the

temperature range of 300–50K. The DC conductivity follows

the semi conducting behavior and is found to decrease with

Figure 4. VSM data of ferric oxide (curve a) and PEDOT–

ferric oxide (curve b).This figure is available in colour online at

www.interscience.wiley.com/journal/pat


temperature. The room temperature conductivity of the

composite was recorded, as 0.4 S/cm while that of PEDOT–

DBSA was 0.02 S/cm. Several models have been used to

explain the conductivity behavior in the polymer. According

to Arrhenius law, conductivity variation follows the relation

sðTÞ ¼ sc exp½�ðEF � ECÞ=KT� ð1Þwhere EF is the Fermi energy, EC is the mobility edge, and scis the conductivity at the mobility edge. Figure 5 (curve a)

shows the lns versus. T�1 plot and its linearity factor is

calculated to be 0.9784 which shows that the Arrhenius

model is not fully applicable for explaining the conductiv-

ity mechanism as in the case of normal semiconductors.

Many other models are also established to explain the con-

ductivity variations of conducting polymers but it is

observed that for the low temperature range of 300–1.8K,

the conductivity studies are best studied by VRH (variable

range hopping) model which follows Mott’s equation36–38

sðTÞ ¼ so exp½�ðTo=TÞ1=g � ð2Þwhere T0 is the Mott characteristic temperature and can be

expressed as

To ¼ 8a=kBNðEFÞZ ð3Þand sO is the conductivity at T¼1

R ¼ ½ap=KBTNðEFÞ��1=2 ð4Þwhere a�1 is the localization length which can be determined

from the magneto conductance data. From the observed

values of T0 and so, one can calculate N(EF) density of states,

R, the average hopping distance with the use of Equations (3)

and (4). Exponent g in Equation (2) is the dimensionality

factor having values 2, 3, and 4 for 1-dimension, 2-dimensions,

and 3-dimension conduction mechanism, respectively. In this

paper, lns versus temperature with different values of g as 2,

3, and 4 have been plotted as shown in Fig. 5 (curves b, c, and

d). It is observed that the conductivity data fit for the

one-dimensional VRH model with g ¼ 2 with a linearity

factor of 0.99957 as compared to the linearity factors of 0.9985

and 0.9966 for two and three-dimensional hoping conduc-

tion, respectively. From the plots, the calculated value of so is

7.06 S/cm and To is 2438.4K. Thus from the above data, it

was observed that 1D-VRH model is suitable for the

conduction mechanism of the PEDOT–g-Fe2O3 composite.

Microwave studies in P-Band (12.4–18GHz)Shielding effectiveness of a material is defined as the ratio of

transmitted power to incident power, hence for SEmeasured

in decibel (dB) it is given by

SE ¼ 10 log Pi=Pt ð5Þwhere Pi (Ei) and Pt (Et) are the power (electric field) of

incident and transmitted EM waves, respectively. For a

single layer of shielding material, the SE is the sum of

contribution due to reflection (SER), absorption (SEA)and

multiple reflection (SEM) and can be given by

SE ¼ SER þ SEA þ SEM ðdBÞ ð6Þ

The S11 or (S22) and S12 or (S21) parameters of the two-port

network system represent the reflection and transmission

coefficients, respectively. According to the analysis of


DOI: 10.1002/pat

Figure 5. Variation of conductivity with respect to temperature; plot of lns versus T�1 (curve a), lns versus

T�1/2 (curve b), lns versus T�1/3 (curve c) and lns versus T�1/4 (curve d).

Figure 6. Variation of shielding effectiveness due to absorp-

tion (SEAeff) and shielding effectiveness due to reflectance

(SER) with frequency in P-band (12.4–18 GHz) of PEDOTand

PEDOT–ferrite composite. This figure is available in colour

online at www.interscience.wiley.com/journal/pat

234 K. Singh et al.

S parameters, transmittance (T), reflectance (R), and

absorbance (A) through the shielding material can be

described as

T ¼ S12j j2¼ S21j j2 ð7Þ

R ¼ S11j j2¼ S22j j2 ð8Þ

A ¼ 1� R� T ð9Þ

Here, it is noted thatA is givenwith respect to the power of

the incident EM wave. If the effect of multiple reflection

between both interfaces of the material is negligible, the

relative intensity of the effectively incident EM wave inside

thematerials after reflection is based on the quantity as 1�R.

Therefore, the effective absorbance (Aeff) can be described as

Aeff¼ (1�R�T)/(1�R) with respect to the power of the

effectively incident EMwave inside the shielding material. It

is convenient that reflectance and effective absorbance are

expressed as the form of�10 log (1�R) and�10 log (1�Aeff)

in decibel (dB),39 respectively, which provide the SEA as

follows:

SER ¼ �10 logð1� RÞ ð10Þ

SEA ¼ �10 logð1� AeffÞ ¼ �10 logðT=1� RÞ ð11Þ

Figure 6 shows the measured EMI SEs of the PEDOT–DBSA

and the PEDOT–g-Fe2O3 composite in the 12.4–18GHz range.

The SER and SEA values calculated by Equations 10 and 11 for


PEDOT–DBSA are 1.63 dB and 8.41 dB at 15.2GHz respect-

ively, while in the case of PEDOT–g-Fe2O3 composite the

calculated values of SER and SEA are 3.82 dB and 20.7 dB,

respectively. These results suggest that the microwave


DOI: 10.1002/pat


absorption loss of the PEDOT–g-Fe2O3 composite is better

than the PEDOT polymer which can find its applications as a

futuristic microwave absorbing material.

CONCLUSIONS

The composite PEDOT–g-Fe2O3 synthesized by the emulsion

polymerization has shown ferrimagnetic behavior having a

magnetization value of 20.56 emu/g and moderate conduc-

tivity of 0.4 S/cm following the 1D-VRH model with

enhanced thermal stability than PEDOT–DBSA synthesized

without g-Fe2O3. The enhancement in the thermal behavior

of the composite is due to some complex formation between

Fe and S of the thiophene ring. The conducting PEDOT–

g-Fe2O3 composite possessing moderate conductivity with

magnetic behavior can be used in many applications, e.g., in

the field of shielding of electronic equipments from

electromagnetic pollution in the microwave range. Our fur-

ther studies are concentrating on developing conducting

ferrite coatings which can be used as a protective sheath

coating suitable for RAM applications.

AcknowledgmentsThe authors express their thanks to Dr. Harikishan for

recording the conductivity data and Dr. R.K. Kotnala for

doing the magnetization measurements of the samples.

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Poly (3,4-ethylenedioxythiophene) γ-Fe2O3 polymer composite–super paramagnetic behavior and variable range hopping 1D conduction mechanism–synthesis and characterization