Nanostructured Materials with Conducting and Magnetic Properties: Preparation of...

Composite Interfaces 18 (2011) 259ndash274brillnlci

Nanostructured Materials with Conducting and MagneticProperties Preparation of MagnetiteConducting

Copolymer Hybrid Nanocomposites byUltrasonic Irradiation

Yuvaraj Haldorai Van Hoa Nguyen Quang Long Pham and Jae-Jin Shim lowast

School of Display and Chemical Engineering Yeungnam University GyeongsanGyeongbuk 712-749 Korea

Received 17 February 2011 accepted 15 March 2011

AbstractConducting copolymer poly(aniline-co-p-phenylenediamine) [poly(Ani-co-pPD)] and surface-modifiedmagnetite (Fe3O4) composites were synthesized by ultrasonically-assisted chemical oxidative polymer-ization Fe3O4 nanoparticles were surface-modified with silane coupling agent methacryloxypropyl-trimethoxysilane (MPTMS) in order that they would be well dispersed for the reaction process It wasalso found that the aggregation of Fe3O4 nanoparticles could be reduced under ultrasonic irradiation TEManalysis confirmed that the resulting poly(Ani-co-pPD)Fe3O4 nanocomposite showed corendashshell morphol-ogy in which Fe3O4 nanoparticles were well dispersed The incorporation of Fe3O4 in the nanocompositeswas endorsed by FT-IR The nanocomposites were also confirmed by UV-visible TGA and XRD Con-ductivity of the nanocomposites was found to be in the range of 702 times 10minus4ndash654 times 10minus6 Scm Highersaturated magnetization of 12 emug was observed for composite with 20 Fe3O4copy Koninklijke Brill NV Leiden 2011

KeywordsAniline p-phenylenediamine Fe3O4 oxidative polymerization ultrasonic irradiation superparamagnetic

1 Introduction

The nanocomposites of superparamagnetic materials and conjugated conductingpolymers have attracted great interest due to their potential applications in batterieselectrochemical display devices electromagnetic interference shielding electro-magnetorheological fluids and microwave absorbing materials drug carriers cellseparation nonlinear optical materials sensors etc Among conducting polymerspolyaniline (PANI) is a promising candidate for practical application because of

To whom correspondence should be addressed E-mail jjshimyuackr

copy Koninklijke Brill NV Leiden 2011 DOI101163092764411X570851

260 Y Haldorai et al Composite Interfaces 18 (2011) 259ndash274

its good environmental stability [1ndash3] ease of preparation high temperature resis-tance and tunable electrical conductivity from conductor to insulator with variouskinds and concentration of dopant Iron oxide is a well-known magnetic mate-rial Thus a PANIiron oxide composite hopefully possesses both electrical andmagnetic properties Several approaches have been developed to prepare such acomposite blending PANI and iron oxide in a solid state or liquid medium [4]coprecipitating a suspension containing Fe2+ Fe3+ and PANI by adjusting the pHvalues to precipitate Fe2+ and Fe3+ into maghemite and magnetite [5 6] and insitu polymerization of a monomer in the presence of iron oxide particles [7ndash12]For in situ polymerization the challenges are how to avoid the aggregation of ironoxide nanoparticles and the large loss of iron oxide Wan et al [5] successfullysynthesized γ -Fe2O3ndashPANI nanomembrane with high conductivity and high satu-rated magnetization By wrapping the magnetic fluid with PANI Deng et al [13]prepared PANIFe3O4 nanospheres with corendashshell structure Yang and cowork-ers [14] synthesized the composites of PANI doped by dodecylbenzenesulfonic acid(DBSA) with Fe3O4 magnetic nanoparticles in a neutral solution by a lsquomodificationand redopingrsquo method Cheng et al [12] synthesized a Fe3O4ndashPANI nanocom-posite in HCl aqueous solution using SDBS as a dispersant Recently Reddy andcoworkers [15] synthesized organosilane modified magnetitepoly(aniline-co-om-aminobenzenesulfonic acid) composites by chemical oxidative polymerization Theresults indicated that the composites of superparamagnetic Fe3O4 nanoparticles andconductive polymer possessed a good electrical conductivity and magnetic suscepti-bility as well as high transmittance However the main disadvantages of conductingpolymers especially polyaniline are its poor solubility and poor processability bothin melt and solution due to its stiffness in the backbone which limits its further ex-tensive applications in many areas In recent years a great deal of attention hasbeen paid to the synthesis and characterization of copolymers of aniline and itsderivatives [16ndash20] As one of the influential derivatives of PANI poly(p-phenyl-enediamine) (PpPD) has been widely synthesized by electropolymerization andchemical oxidative polymerization [18] The PpPD has demonstrated great po-tentiality for use as electrochromic display materials humidity sensors electrode-modified materials pH response and protection against metal corrosion and soon [21] Among the conducting copolymers poly(aniline-co-p-phenylenediamine)has attracted much attention due to its film forming electronic and electrochromicproperties [17]

Ultrasound has been widely used in chemical reactions such as dispersion emul-sifying crushing organic synthesis and polymerization This is because ultrasoniccavitation can generate local temperatures as high as 5000 K and local pressuresas high as 500 atm with heating and cooling rates greater than 109 Ks whichis a very rigorous environment Ultrasonic irradiation is a useful technique forpreparing novel materials with unusual properties The application of ultrasound toprepare conducting PANI [22ndash24] and conducting polymerinorganic oxide com-posites [25ndash27] has been reported Compared to PANI prepared by conventional

Y Haldorai et al Composite Interfaces 18 (2011) 259ndash274 261

stirring PANI prepared by ultrasonic irradiation has higher conductivity or highercrystallinity More recently we prepared conducting copolymersilica nanocom-posites [28] with a corendashshell structure by ultrasonically-assisted in situ emulsionpolymerization Although the ultrasonic irradiation has previously been success-fully used for the preparation of conducting polymerinorganic oxide composites[25ndash28] to the best of our knowledge no work has been published on preparationof poly(Ani-co-pPD)Fe3O4 hybrid nanocomposites

In the present study both ultrasonic irradiation and surface-modification tech-nique are employed to prepare poly(Ani-co-pPD)Fe3O4 hybrid nanocompositesWe use MPTMS to form a silane monolayer on the surface of Fe3O4 nanoparti-cles which allows further surface polymerization to form hybrid composites Thenanocomposites are characterized by a number of techniques including FT-IR FE-TEM FE-SEM UV-visible spectroscopy TGA XPS and XRD In addition theelectrical and magnetic properties of nanocomposites are investigated

2 Experimental

21 Materials

Magnetite (Fe3O4) nanoparticles (with an average particle size of lt50 nm) andmethacryloxypropyltrimethoxysilane (MPTMS) were obtained from Aldrich Ani-line and p-phenylenediamine were obtained from TCI Aniline was distilled underreduced pressure and stored at 0C for use Potassium persulfate and all other or-ganic reagents were of analytical grade and used as received

22 Surface-Modification of Fe3O4 Nanoparticles

Grafting reaction was carried out according to the procedure given in the litera-ture [29] After dispersing 5 g of Fe3O4 nanoparticles in 100 ml of toluene 10 gof MPTMS was added and the resulting solution was stirred for 24 h under argonatmosphere Modified Fe3O4 was isolated by centrifugation and washed repeatedlywith toluene Finally it was dried at 40C under vacuum for 24 h

23 Synthesis of Neat Copolymer by Ultrasonic Irradiation

In a typical experiment monomers aniline (002 M) and p-phenylenediamine(002 M) were dissolved in 01 M HCl and the resulting solution was sonicated for5 min Then it was deoxygenated with oxygen-free nitrogen for 3 min and coolingwater circulated around the vessel to maintain a lower temperature of around 10CFinally potassium persulfate (004 M) solution was added dropwise to initiate thepolymerization Ultrasonic irradiation was carried out with the probe of the ultra-sonic horn immersed directly into the solution (ultasonic power output 300 W)After 2 h of ultrasonic irradiation the reaction was stopped and terminated by pour-ing the reaction mixture into acetone whereupon the copolymer precipitated outThe resulting product was filtered and thoroughly washed with deionized water andvacuum dried at 40C for 24 h


24 Preparation of Poly(Ani-co-pPD)Fe3O4 Nanocomposites by UltrasonicIrradiation

In a typical experiment monomers aniline (002 M) and p-phenylenediamine(002 M) were dissolved in 01 M HCl The desired amount of surface-modifiedFe3O4 nanoparticles (25 5 10 and 20 ww based on the comonomer content)were then dispersed in the solution using an ultrasonicator for 5 min Then it wasdeoxygenated with oxygen-free nitrogen for 3 min and water circulated around thevessel to maintain a lower temperature of around 10C Finally potassium per-sulfate solution was added dropwise The molar ratio of initiator to comonomerwas 11 in all the experiments After 2 h of ultrasonic processing the reaction wasstopped The purification procedure was same as for the neat copolymer

25 Characterization

FT-IR characterization was performed using an Excalibur Series FTS 3000(BioRad) spectrometer UV-visible spectra of the diluted nanocomposite disper-sions in the 200ndash800 nm range were obtained using an Agilent 8453 UV-visiblespectrophotometer FE-TEM images were obtained on a field emission transmis-sion electron microscope (Technai G2 F20) operated with an accelerating voltageof 200 kV The samples were prepared as follows a small amount of the nanocomp-site sample was dispersed in alcohol under sonication for 5 min One drop ofthe dilute suspension of copolymerFe3O4 colloid was deposited on a copper gridcoated with a carbon membrane Microscopic images of nanocomposites were ob-tained by a Hitachi S-4200 field emission scanning electron microscope (FE-SEM)Prior to imaging the samples were sputter-coated with argon plasma XRD patternswere collected on a powder X-ray diffractometer (PANalytical XrsquoPert-PRO MPD)with Cu Kα radiation Thermogravimetric analysis (TGA) and differential scanningcalorimetry (DSC) studies were performed on a TA instruments (SDT Q600 ana-lyzer) from 30 to 800C at a heating rate of 10Cmin under nitrogen atmosphereX-ray photoelectron spectroscopy (XPS) measurements were performed with aULVAC-PHI electron spectrometer (Quantera SXM) with an Al X-ray sourceRoom temperature conductivities of the pressed pellets were measured by a HallEffect Measurement System (Ecopia HMS-5000) using the van der Pauw four-probe method Magnetic characterization was performed using a magnetic propertymeasurement system (MPMS XL 70 Quantum design) at room temperature Theultrasonic irradiation device (VCX 750 Sonic and Mater Co) was equipped witha standard titanium horn with replaceable tip diameter of 13 mm and temperaturecontroller The energy output of the probe was set to 300 W

3 Results and Discussion

It is well known that the pristine Fe3O4 nanoparticles tend to aggregate due tothe high surface energy and an anisotropic dipolar attraction between the magneticnanoparticles Therefore the Fe3O4 nanoparticles were not easily dispersible but


Figure 1 FT-IR spectra of the (a) pristine Fe3O4 and (b) MPTMS-modified Fe3O4

were dispersed after modification with silane coupling agent In addition ultra-sound has been applied to disperse crush and activate the nanoparticles Surface-modification of Fe3O4 nanoparticles using MPTMS forms a silane monolayer onthe surface of Fe3O4 and also prevents the condensation of nanoparticles during thedrying process The surface-modified Fe3O4 was characterized by FT-IR (Fig 1)The spectrum of pristine Fe3O4 (Fig 1(a)) had one major band at 573 cmminus1 as-cribed to the FendashO stretching vibration The spectrum of surface-modified Fe3O4(Fig 1(b)) showed characteristic absorption bands C=O (1718 cmminus1) C=C(1637 cmminus1) (SindashO) (996 cmminus1) and FendashO (580 cmminus1) which indicate the avail-ability of silane group on the surface of Fe3O4 [30] A broad absorption peakcentered at 3330 cmminus1 is attributed to the existence of hydroxyl groups (ndashOH) onthe surface of Fe3O4 nanoparticles The principal procedure involved in the synthe-sis of poly(Ani-co-pPD)Fe3O4 hybrid nanocomposite consists of two steps thefirst step is the surface-modification of Fe3O4 nanoparticles in order that they willdisperse well and the second step is the ultrasonically-assisted chemical oxidativepolymerization of comonomer in the presence of nanoparticles Hybrid nanocom-posites with different loadings of Fe3O4 (25 5 10 and 20 ww) with respect tocomonomer were also carried out

FT-IR spectra of the neat copolymer and poly(Ani-co-pPD)Fe3O4 hybridnanocomposite (20 Fe3O4) are shown in Fig 2 It is clear that the copolymerand nanocomposite showed very similar spectra In the case of the nanocompositethe band centered at 3421 cmminus1 is attributed to the characteristic NndashH stretchingvibration of the secondary amine groups of the copolymer [18 19] The peaks at1583 and 1497 cmminus1 are assigned to C=C stretching vibration of quinoid and ben-zenoid rings respectively [26 31] The peak at 1303 cmminus1 is attributed to the CndashNstretching vibration of secondary amine The peaks appeared at 609 and 1110 cmminus1

are attributed to FendashO and FendashOndashSi stretching modes respectively indicating the


Figure 2 FT-IR spectra of the (a) neat copolymer and (b) poly(Ani-co-pPD)Fe3O4 nanocomposite(20 Fe3O4)

Figure 3 FE-SEM images of the (a) neat copolymer and (b) poly(Ani-co-pPD)Fe3O4 nanocompos-ite (20 Fe3O4)

existence of Fe3O4 in the composite However the incorporation of Fe3O4 nanopar-ticles leads to the shift of some FT-IR bands of the copolymer This may be ascribedto the fact that the interaction of Fe3O4 and copolymer was followed by the forma-tion of H-bonding between the proton on NndashH and the oxygen atom on the Fe3O4surface [32]

FE-SEM images of the neat copolymer and poly(Ani-co-pPD)Fe3O4 hybridnanocomposite (20 Fe3O4) are shown in Fig 3 From Fig 3(a) one can see thatthe bulk copolymer synthesized without Fe3O4 showed a typical morphology Thenanocomposite (Fig 3(b)) showed a growth of chain pattern of copolymer and theFe3O4 nanoparticles present between the junctions of the copolymer chain networkcould be observed in the picture The phase contrast of the nanocomposite ap-


Figure 4 FE-TEM images of the (a) pristine Fe3O4 (b) poly(Ani-co-pPD)Fe3O4 nanocomposite(20 Fe3O4) and (c) close inspection

pears to be less pronounced owing to the engulfment of Fe3O4 nanoparticles by thecopolymer The micrograph of the composite exhibits a two-phase system where thebright phase corresponds to the existence of Fe3O4 while the dark phase constitutesthe copolymer Usually nanocomposites show globular clusters of polymers andinorganic fillers To ascertain the physical nature of Fe3O4 in the nanocompositemore clearly the FE-TEM images of pristine Fe3O4 and poly(Ani-co-pPD)Fe3O4hybrid nanocomposite (20 Fe3O4) are depicted in Fig 4 The commercially avail-able pristine Fe3O4 nanoparticles were slightly aggregated (Fig 4(a)) which isconsistent with the supplierrsquos statement Because of the smaller dimensions ofthe nanoparticles it is possible that several nanoparticles are coalesced to formlarge Fe3O4 particles This should be attributed to the high surface energy andmagnetic dipole interactions between the Fe3O4 nanoparticles The morphologyof colloidal poly(Ani-co-pPD)Fe3O4 nanocomposite particles obtained were rela-tively spherical in shape in which Fe3O4 nanoparticles were well dispersed in thecopolymer matrix The dispersion of Fe3O4 nanoparticles in the copolymer matrixis due to (i) the effect of ultrasonication and (ii) silanation By means of ultra-sonic processing the aggregated nanoparticles were broken down and the particles


were redispersed in aqueous solution on a nanoscale in the reaction system At thesame time the comonomer molecules were absorbed on the surface of Fe3O4 parti-cles and then polymerized to form the corendashshell nanocomposite Upon silanationcompacted silane layers are formed around the Fe3O4 nanoparticles which spaceseach of the magnetic nanoparticles far apart and results in the surface-modifiednanoparticles being well dispersed in the copolymer matrix The aggregation isminimized due to the shielding of coated silane layers for the magnetic dipole inter-actions In the nanocomposite we noted that there are two kinds of particles freecopolymer particles with relatively larger size and the copolymer encapsulatedFe3O4 nanocomposite particles with a smaller size All the Fe3O4 nanoparticleswere encapsulated by the copolymer From the close inspection of nanocomposite(Fig 4(c)) it is clear that the darker-contrast Fe3O4 nanoparticles were coated bythe lighter-contrast copolymer owing to the different electron penetrability

UV-visible spectra were obtained by dispersing the neat copolymer andpoly(Ani-co-pPD)Fe3O4 hybrid nanocomposite (20 Fe3O4) in N-methyl pyrroli-done (NMP) as shown in Fig 5 The copolymer exhibits two major absorptionbands The first absorption band in the region of 310 nm is assigned to the πndashπlowasttransition of the benzenoid ring of the copolymer It is related to the extent of conju-gation between the phenyl rings along the copolymer chain The second absorptionband at 575 nm is due to the electronic transition of quinoid imine structures and thismight be assigned to the polyaniline segments [2 3 17 19] Similar characteristicbands were also observed for poly(Ani-co-p-PD)Fe3O4 nanocomposite Howeverthe absorption band at 575 nm is shifted to 540 nm This may be attributed to the in-teraction between Fe3O4 nanoparticles and the copolymer chains which effectivelyimproves the degree of electron delocalization of copolymer chains [33]

Figure 5 UV-visible spectra of the neat copolymer and poly(Ani-co-pPD)Fe3O4 nanocomposite(20 Fe3O4)


(a) (b)

Figure 6 TGA and DSC curves of the (a) neat copolymer and (b) poly(Ani-co-pPD)Fe3O4nanocomposite (20 Fe3O4) in nitrogen

Thermal stability of poly(Ani-co-pPD)Fe3O4 hybrid nanocomposite (20Fe3O4) was analyzed by TGA in nitrogen atmosphere and the results are comparedwith the neat copolymer as shown in Fig 6 The two samples followed a similardecomposition trend showing a gradual weight loss The copolymer exhibits atwo-step weight loss The first weight-loss step in the TGA curve of copolymer ob-served between 170 and 260C corresponds to the loss of dopant The second stepbetween 500 and 650C corresponds to the final degradation of copolymer How-ever it was found that the thermal stability of nanocomposite is higher than thatof the neat copolymer which was obviously related to the existence of thermallystable Fe3O4 The residual mass left at 800C was found to be 40 and 56 for thecopolymer and nanocomposite respectively The improved thermal stability shouldbe attributed to the interaction between Fe3O4 and copolymer chains DSC curvesof the neat copolymer and poly(Ani-co-pPD)Fe3O4 hybrid nanocomposite (20Fe3O4) are also presented in Fig 6 The main endothermic peak between 200 and270C can be attributed to the morphological changes and disruption of inter andintra-molecular hydrogen bonding

XRD patterns of the neat copolymer and poly(Ani-co-pPD)Fe3O4 hybridnanocomposite (20 Fe3O4) are depicted in Fig 7 The spectrum of copolymerdepicted two broad peaks at 2θ = 189 and 261 as shown in Fig 7(a) mdash this sug-gests that the copolymer is partially crystalline The maximum peak at 189 maybe ascribed to the momentum transfer periodicity parallel to the copolymer chainwhereas the latter peak at 261 may be caused by the periodicity perpendicularto the copolymer chain [19 34] The XRD pattern of nanocomposite (Fig 7(b))shows that there are two obvious phases the copolymer phase and Fe3O4 phasewhich has several sharp peaks at 2θ = 302356433536573 and 623


Figure 7 XRD curves of the (a) neat copolymer and (b) poly(Ani-co-pPD)Fe3O4 nanocomposite(20 Fe3O4) Pristine Fe3O4 is given in the inset

In the nanocomposite the main peaks are similar to the main peaks of pristineFe3O4 (Fig 7 inset) The broad diffraction peaks of copolymer are very weekshowing that the crystallinity of copolymer in the composite is much lower thanthat of neat copolymer Thus the presence of Fe3O4 in the polymerization systemstrongly affects the crystalline behavior of formed copolymer that is the interactionof copolymer and Fe3O4 nanoparticles restricts the crystallization of copolymer

In the present work we used XPS to determine the surface-composition ofnanocomposite Figure 8 shows the XPS spectra of the neat copolymer andpoly(Ani-co-pPD)Fe3O4 hybrid nanocomposite (20 Fe3O4) Both the samplesshowed three main peak signals such as C1s N1s and O1s The binding energy (BE)of Fe2p peak is about 702ndash730 eV but this is not found in Fig 8(b) this indicatesthat there is no elemental Fe on the surface of the nanocomposite Therefore the ab-sence of Fe2p peak in the composite confirmed that all the Fe3O4 nanoparticles wereencapsulated by the copolymer However the peaks with particular binding energiesof every element in the composite were slightly shifted because of the change in en-vironment The main peaks of copolymer (C1s N1s and O1s) with binding energiesof 28284 39913 and 53026 eV were shifted to 28496 40125 and 53238 eVrespectively in the composite

The magnetic property of poly(Ani-co-pPD)Fe3O4 hybrid nanocomposites isshown in Fig 9 Saturation of magnetization (Ms) of pristine Fe3O4 and surface-


(a)

(b)

Figure 8 Survey XPS spectrum of the (a) neat copolymer and (b) poly(Ani-co-pPD)Fe3O4nanocomposite (20 Fe3O4)

modified Fe3O4 was found to be 68 and 64 emug respectively The difference inMs between the pristine and surface-modified Fe3O4 suggests that the presence ofsilane layers on the surface of Fe3O4 nanoparticles could be the reason for the low-ering of Ms values It is well known that when Fe3O4 nanoparticles are embeddedinto a nonmagnetic matrix (such as polymers gold silica) there can be a decrease inMs values of the resulting material [35ndash38] There are several reasons for loweringthe Ms of coated magnetic nanoparticles [39ndash41] Dipole de-coupling by opposingthe magnetization field large percentage of surface spins disordered magnetizationorientation at the particle surface surface anisotropy and any crystalline disorderwithin the surface layer have been suggested as reasons for the decrease in Msvalue of coated magnetic materials


(a) (b)

Figure 9 Magnetic property of the (a) pristine Fe3O4 and (b) nanocomposites

Preliminary measurements on the magnetic property showed that the nanocom-posites are superparamagnetic The magnetic property increases with increasingFe3O4 content in the composites The Ms of composites increased from 06 to12 emug with the increase of Fe3O4 content from 25 to 20 It is worth notingthat the measured saturated magnetization of nanocomposites is considerably lowerthan the value measured from the pristine Fe3O4 nanoparticles (Ms = 68 emug)The reduced magnetization could be attributed to the small particle surface effect[8] This interesting feature was also observed in other polymer composites withnanosized superparamagnetic particles [7 9 31] For example Ms is 6 emugfor PANIFe3O4 (268 Fe3O4) [42] 484 emug for PANIFe3O4 (4386 wtof Fe3O4) [9] 1162 emug for polyaniline copolymer (21 wt of Fe3O4) [15]and 8 emug for polypyrroleFe2O3 (1694 wt of Fe2O3) [43] So far no defi-nite explanation of this discrepancy has been advanced However Kryszewski andJeszka [7] pointed out that the interactions between the polymer matrix and ironoxide nanoparticles may play an important role in the superparamagnetic behaviorof composites The specific morphology of copolymer (ie how the nanoparticlesare coated by copolymer chains) may strongly influence the surface interactions atthe magnetic nanoparticles Therefore the measured values of Ms are so differentdue to the different interactions at the interphases in these nanocomposites The Msof samples obtained through ultrasonically-assisted chemical oxidative polymeriza-tion is given in Table 1

Electrical conductivity measurements of the neat copolymer and poly(Ani-co-pPD)Fe3O4 nanocomposites were carried out using a standard four-point probeapparatus The concentration of Fe3O4 nanoparticles significantly affects conduc-tivity of the resulting nanocomposites The conductivity of conjugated polymerbased composite nanostructures is mainly dependent on the doping level of poly-mer compactness of the sample crystallinity size morphology of the nanocom-posite and preparation method etc The conductivity of neat copolymer was found


Table 1Electrical and magnetic properties

Samples Conductivity (Scm) Saturated magnetization (emug)

Neat copolymer 182 times 10minus3 ndashPoly(Ani-co-pPD)Fe3O4 (25) 702 times 10minus4 06Poly(Ani-co-pPD)Fe3O4 (5) 103 times 10minus4 105Poly(Ani-co-pPD)Fe3O4 (10) 561 times 10minus5 15Poly(Ani-co-pPD)Fe3O4 (20) 654 times 10minus6 12Pristine Fe3O4 ndash 68Surface-modified Fe3O4 ndash 64

to be 182 times 10minus3 Scm while that of nanocomposite with 25 and 20 Fe3O4 wasfound to be 702 times 10minus4 and 654 times 10minus6 Scm respectively (Table 1) This ob-servation agrees with some earlier reports [9 42] The decrease in the conductivityof nanocomposites with increasing Fe3O4 concentration can be attributed to the in-sulating behavior of Fe3O4 in the core of nanoparticle which hinders the chargetransfer thereby lowering the conductivity

4 Conclusions

In this report we demonstrated a simple method to synthesize surface-modifiedFe3O4poly(Ani-co-pPD) hybrid nanocomposites via ultrasonically-assisted chem-ical oxidative polymerization Under ultrasonic irradiation the aggregates of Fe3O4nanoparticles were broken down and the particles were redispersed in aqueous so-lution on the nanoscale in the reaction system FE-TEM measurement proved thatthe Fe3O4 nanoparticles were well dispersed in the copolymer matrix FT-IR spec-tra suggested that the nanocomposite materials were formed by strong interactionbetween the copolymer chains and Fe3O4 nanoparticles It is noteworthy that thenanocomposites are thermally stable electrically conductive and exhibit superpara-magnetism Such attractive features make the nanocomposites promising candidatesfor applications in optoelectronic and microwave absorption devices Works on theexploration of such applications are underway

Acknowledgement

This work was supported by the Yuengnam University research grant in 2009

References

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2 X G Li M R Huang and W Duan Novel multifunctional polymers from aromatic diamines byoxidative polymerizations Chem Rev 102 2925ndash3030 (2002)


3 X G Li A Li and M R Huang Facile high-yield synthesis of polyaniline nanosticks withintrinsic stability and electrical conductivity Chem Eur J 14 10309ndash10317 (2008)

4 B Z Tang Y H Geng J Y W Lam B S Li X B Jing X H Wang F S Wang A B Pakhomovand X X Zhang Processible nanostructured materials with electrical conductivity and magneticsusceptibility preparation and properties of maghemitepolyaniline nanocomposites films ChemMater 11 1581ndash1589 (1999)

5 M X Wan W X Zhou and J C Li Composite of polyaniline containing iron oxides withnanometer size Synth Met 78 27ndash31 (1996)

6 M X Wan and J C Li Synthesis and electricalndashmagnetic properties of polyaniline compositesJ Polym Sci Part A Polym Chem 36 2799ndash2805 (1998)

7 M Kryszewski and J K Jeszka Nanostructured conducting polymer compositesndashsuperparamag-netic particles in conducting polymers Synth Met 94 99ndash104 (1998)

8 Z M Zhang and M X Wan Nanostructures of polyaniline composites containing nano-magnetSynth Met 132 205ndash212 (2003)

9 J G Deng C L He Y X Peng J H Wang X P Long P Li and A S C Chan Magnetic andconductive Fe3O4ndashpolyaniline nanoparticles with corendashshell structure Synth Meth 139 295ndash301(2003)

10 J G Deng X B Ding W C Zhang Y X Peng J H Wang X P Long P Li and A S C ChanMagnetic and conducting Fe3O4ndashcross-linked polyaniline nanoparticles with corendashshell structurePolymer 43 2179ndash2184 (2002)

11 Q L Yang J Zhai Y L Song M X Wan L Jiang W G Xu and Q S Li Electrical andmagnetic properties of nanocomposites of conducting polyaniline and γ -Fe2O3 nanoparticlesChem J Chinese Univ 24 2290ndash2292 (2003)

12 G E Cheng K X Huang and H Z Ke Preparation and characterization of conductive andmagnetic PANI nano-composite Earth Sci J Chinese Univ Geosci 29 65ndash68 (2004)

13 J Deng Y Peng X Din J Wang X Long P Li and X Chen Preparation and characterizationof magnetic polyaniline microspheres Chen Chinese J Chem Phys 15 149ndash152 (2002)

14 Q Yang Y Song M Wan L Jiang Q Li and W Xu Synthesis and characterization of compositeof conducting polyaniline with Fe3O4 magnetic nanoparticles Chem J Chinese Univ 23 1105ndash1109 (2002)

15 K R Reddy K P Lee A I Gopalan and H D Kang Organosilane modified magnetitenanoparticlespoly(aniline-co-om-aminobenzenesulfonic acid) composites synthesis and charac-terization React Funct Polym 67 943ndash954 (2007)

16 P Savitha and D N Sathyanarayana Synthesis and characterization of electrically conductingpoly(om-toluidine-co-om-aminoacetophenone) copolymers J Polym Sci Part A Polym Chem42 4300ndash4310 (2004)

17 X G Li H Y Wang and M R Huang Synthesis film-forming and electronic properties ofphenylenediamine copolymers displaying an uncommon tricolor Macromolecules 40 1489ndash1496(2007)

18 J Prokes J Stejskal I Krivka and E Tobolkova Aniline-phenylenediamine copolymers SynthMeth 102 1205ndash1206 (1999)

19 Q F Lu M R Huang and X G Li Synthesis and heavy-metal-ion sorption of pure sul-fophenylenediamine copolymer nanoparticles with intrinsic conductivity and stability Chem EurJ 13 6009ndash6018 (2007)

20 X G Li Q F Lu and M R Huang Self-stabilized nanoparticles of intrinsically conductingcopolymers from 5-sulfonic-2-anisidine Small 4 1201ndash1209 (2008)

21 K S Suslick Sonochemistry Science 147 1439ndash1445 (1990)


22 H S Xia and Q Wang Synthesis and characterization of conductive polyaniline nanoparticlesthrough ultrasonic assisted inverse microemulsion polymerization J Nanopart Res 3 401ndash411(2001)

23 M Atobe A Chowdhury T Fuchigami and T Nonaka Preparation of conducting polyanilinecolloids under ultrasonication Ultrason Sonochem 10 77ndash80 (2003)

24 H Liu X B Hu J Y Wang and R I Boughton Structure conductivity and thermopower ofcrystalline polyaniline synthesized by the ultrasonic irradiation polymerization method Macro-molecules 35 9414ndash9419 (2002)

25 H S Xia and Q Wang Ultrasonic irradiation a novel approach to prepare conductive polyani-linenanocrystalline titanium oxide composites Chem Mater 14 2158ndash2165 (2002)

26 H S Xia and Qi Wang Preparation of conductive polyanilinenanosilica particle compositesthrough ultrasonic irradiation J Appl Polym Sci 87 1811ndash1817 (2003)

27 G Qui Qi Wang and M Nie PolyanilineFe3O4 magnetic nanocomposite prepared by ultrasonicirradiation J Appl Polym Sci 102 2107ndash2111 (2006)

28 Y Haldorai P Q Long S K Noh W S Lyoo and J J Shim Ultrasonically assisted in situemulsion polymerization a facile approach to prepare conducting copolymersilica nanocompos-ites Polym Adv Technol doi 101002pat 1577 (in press)

29 N Tsubokawa K Maruyama Y Sone and M Shimomura Graft polymerization of acrylamidefrom ultrafine silica particles by use of a redox system consisting of ceric ion and reducing groupson the surface Polym J 21 475ndash481 (1989)

30 H Yuvaraj M H Woo E J Park Y T Jeong and K T Lim Polypyrroleγ -Fe2O3 magneticnanocomposites synthesized in supercritical fluid Eur Polym J 44 637ndash644 (2008)

31 Y Furukawa F Ueda Y Hyodo I Harada T Nakajima and T Kawagoe Vibrational spectra andstructure of polyaniline Macromolecules 21 1297ndash1305 (1988)

32 G Qiu Qi Wang and M Nie PolypyrrolendashFe3O4 magnetic nanocomposite prepared by ultra-sonic irradiation Macromol Mater Eng 291 68ndash74 (2006)

33 F Wang G Wang S Yang and C Li Layer-by-layer assembly of aqueous dispersiblehighly conductive poly(aniline-co-o-anisidine)poly(sodium 4-styrenesulfonate)MWNTs corendashshell nanocomposites Langmuir 24 5825ndash5831 (2008)

34 J Zhang D Shan and S Mu Chemical synthesis and electric properties of the conducting copoly-mer of aniline and o-aminophenol J Polym Sci Part A Polym Chem 45 5573ndash5582 (2007)

35 J Yang S B Park H G Yoon Y M Huh and S Haam Preparation of poly ε-caprolactonenanoparticles containing magnetite for magnetic drug carrier Intl J Pharm 324 185ndash190 (2006)

36 J Guo W Yang C Wang J He and J Chen Poly(N-isopropylacrylamide)-coated lumines-centmagnetic silica microspheres preparation characterization and biomedical applicationsChem Mater 18 5554ndash5562 (2006)

37 H Xu L Cui N Tong and H Gu Development of high magnetization Fe3O4polystyrenesilicananospheres via combined miniemulsionemulsion polymerization J Amer Chem Soc 12815582ndash15583 (2006)

38 Q Yavuz M K Ram M Aldissi P Poddar and H Srikanth Polypyrrole composites for shieldingapplications Synth Meth 151 211ndash217 (2005)

39 J Popplewell and L Sakhnini The dependence of the physical and magnetic properties of mag-netic fluids on particle size J Magn Magn Mater 149 72ndash78 (1995)

40 H R Kodoma A E Berkovitz E J Mcniff and S Foner Surface spin disorder in NiFe2O4nanoparticles Phys Rev Lett 77 394ndash397 (1996)

41 D L L Pelecky and R D Rieke Magnetic properties of nanostructured materials Chem Mater8 1770ndash1783 (1996)


42 Z Zhang M Wan and Y Wei Electromagnetic functionalized polyaniline nanostructures Nan-otechnology 16 2827ndash2832 (2005)

43 X Yang L Xu N S Choon and C S O Hardy Magnetic and electrical properties of polypyrrole-coated γ -Fe2O3 nanocomposite particles Nanotechnology 14 624ndash629 (2003)


its good environmental stability [1ndash3] ease of preparation high temperature resis-tance and tunable electrical conductivity from conductor to insulator with variouskinds and concentration of dopant Iron oxide is a well-known magnetic mate-rial Thus a PANIiron oxide composite hopefully possesses both electrical andmagnetic properties Several approaches have been developed to prepare such acomposite blending PANI and iron oxide in a solid state or liquid medium [4]coprecipitating a suspension containing Fe2+ Fe3+ and PANI by adjusting the pHvalues to precipitate Fe2+ and Fe3+ into maghemite and magnetite [5 6] and insitu polymerization of a monomer in the presence of iron oxide particles [7ndash12]For in situ polymerization the challenges are how to avoid the aggregation of ironoxide nanoparticles and the large loss of iron oxide Wan et al [5] successfullysynthesized γ -Fe2O3ndashPANI nanomembrane with high conductivity and high satu-rated magnetization By wrapping the magnetic fluid with PANI Deng et al [13]prepared PANIFe3O4 nanospheres with corendashshell structure Yang and cowork-ers [14] synthesized the composites of PANI doped by dodecylbenzenesulfonic acid(DBSA) with Fe3O4 magnetic nanoparticles in a neutral solution by a lsquomodificationand redopingrsquo method Cheng et al [12] synthesized a Fe3O4ndashPANI nanocom-posite in HCl aqueous solution using SDBS as a dispersant Recently Reddy andcoworkers [15] synthesized organosilane modified magnetitepoly(aniline-co-om-aminobenzenesulfonic acid) composites by chemical oxidative polymerization Theresults indicated that the composites of superparamagnetic Fe3O4 nanoparticles andconductive polymer possessed a good electrical conductivity and magnetic suscepti-bility as well as high transmittance However the main disadvantages of conductingpolymers especially polyaniline are its poor solubility and poor processability bothin melt and solution due to its stiffness in the backbone which limits its further ex-tensive applications in many areas In recent years a great deal of attention hasbeen paid to the synthesis and characterization of copolymers of aniline and itsderivatives [16ndash20] As one of the influential derivatives of PANI poly(p-phenyl-enediamine) (PpPD) has been widely synthesized by electropolymerization andchemical oxidative polymerization [18] The PpPD has demonstrated great po-tentiality for use as electrochromic display materials humidity sensors electrode-modified materials pH response and protection against metal corrosion and soon [21] Among the conducting copolymers poly(aniline-co-p-phenylenediamine)has attracted much attention due to its film forming electronic and electrochromicproperties [17]

Ultrasound has been widely used in chemical reactions such as dispersion emul-sifying crushing organic synthesis and polymerization This is because ultrasoniccavitation can generate local temperatures as high as 5000 K and local pressuresas high as 500 atm with heating and cooling rates greater than 109 Ks whichis a very rigorous environment Ultrasonic irradiation is a useful technique forpreparing novel materials with unusual properties The application of ultrasound toprepare conducting PANI [22ndash24] and conducting polymerinorganic oxide com-posites [25ndash27] has been reported Compared to PANI prepared by conventional




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Nanostructured Materials with Conducting and Magnetic Properties: Preparation of...

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