Journal of Colloid and Interface Science

Journal of Colloid and Interface Science333(2009)

415–418

Contents lists available at ScienceDirect

Journal of Colloid and Interface Science

https://www.360docs.net/doc/fd11184360.html,/locate/jcis

Short Communication

Synthesis and characterization of poly(3-methyl thiophene)nanospheres

in magnetic ionic liquid

Songmin Shang a,?,Liang Li a,b,?,Xiaoming Yang a,Lei Zheng b

a Institute of Textiles and Clothing,The Hong Kong Polytechnic University,Hung Hom,Kowloon,Hong Kong,PR China

b Key Laboratory for Green Chemical Process of Ministry of Education,School of Materials Science and Engineering,Wuhan Institute of Technology,Wuhan430073,PR China a r t i

c l e i n f o a b s t r a c t

Article history:

Received7October2008 Accepted9January2009 Available online15January2009

Keywords:

Poly(3-methyl thiophene)

Ionic liquid

Nanospheres

Polymers Poly(3-methyl thiophene)nanospheres with their size ranging around50–60nm have been synthesized by simply adding monomers into a magnetic ionic liquid,Bmim[FeCl4].The ionic liquid leads to the formation of uniform nanospheres with a relatively narrow size distribution con?ned to submicrometer-sized domains.The poly(3-methyl thiophene)nanospheres were characterized by FTIR,Raman and thermogravimetric analysis(TGA).Scanning electron microscopy(SEM)was used to show the morphology of the samples.As compared with the conventional solution polymerization method,the polymerization yield and conductivity of the polymers produced in this magnetic ionic liquid system were improved.

?2009Elsevier Inc.All rights reserved.

1.Introduction

Conducting polymers,such as polyaniline,polypyrrole,polythio-phene and their derivatives,have recently given rise to numerous investigations because of their potentially interesting electrical and optical properties controlled by a simple and reversible acid–base doping–dedoping process,which allowed this conducting polymer nanomaterials possibly to be applied in the?elds of electromag-netic interference shielding,organic conductors,actuators,and gas-separation membranes[1–5].In particular,there is an increased drive toward the fabrication of nanostructured and reduced di-mensionality materials,such as thin?lms,tubes,wires,particles,?bers,etc.,due to their promise for improving upon applications that currently use their bulk counterparts materials[6,7].Among conducting polymers,poly(3-methyl thiophene)(P3MT)has been received a signi?cant share of attention.P3MT,as an important derivative of polythiophene,has led to numerous applications in the?elds of microelectronics,optoelectronics,and sensors[8,9] owing to its high conductivity and high tensile strength and?exi-bility.These conducting polymers with various nanostructures can be prepared through either chemical or electrochemical oxidation of the monomer with or without the template[10–12].

Ionic liquids comprised entirely of ions are liquid at ambient temperature and a relatively new class of solvent.They are green solvents and favor doping for the composition of inorganic anions. Ionic liquids are attracting signi?cant attention in many?elds of chemistry and industry because of their unique physicochemical

*Corresponding authors.

E-mail addresses:tcshang@https://www.360docs.net/doc/fd11184360.html,.hk(S.Shang),msell08@https://www.360docs.net/doc/fd11184360.html,(L.Li).properties,such as negligible vapor pressure,low volatility,high thermal and electrochemical stability,and ionic conductivity[13–16].In addition,ionic liquids have been shown to dissolve a wide range of organic and inorganic materials,which allows access to a range of monomers and chemical oxidants at signi?cant con-centrations.Considering the above merits,ionic liquids are ideal media for the synthesis and utilization of conducting polymers as they can exhibit excellent oxidative and reductive stability,and can signi?cantly improve performance and lifetimes when used as the supporting electrolyte and solvent in conducting polymers devices [17–20].

Here,we reported the results on the synthesis and character-ization of poly(3-methyl thiophene)nanospheres in a magnetic ionic liquid(MIL),1-butyl-3-methylimidazolium tetrachloroferrate (Bmim[FeCl4]),as the solvent and https://www.360docs.net/doc/fd11184360.html, is basically a kind of ionic liquid(IL).The only difference between IL and MIL is that the anion of MIL is FeCl?

4

.MIL has the unusual properties of IL. Besides,MIL shows a response to a magnetic?eld.When polymer-ization ofπ-conjugated polymer was carried out in Bmim[FeCl4],

FeCl?

4

moiety could play roles as a synthetic catalyst as well as a dopant.Fourier transform infrared(FTIR),Raman,thermogravimet-ric analysis(TGA)and scanning electronic microscopy(SEM)were used to characterize the P3MT nanospheres.

2.Materials and methods

2.1.Polymerization in magnetic ionic liquid

3-Methyl thiophene monomer and the anhydrous iron(III) chloride were purchased from Aldrich and used without fur-ther puri?cation.Crystalline1-butyl-3-methylimidazolium chloride

0021-9797/$–see front matter?2009Elsevier Inc.All rights reserved. doi:10.1016/j.jcis.2009.01.021

416S.Shang et al./Journal of Colloid and Interface Science333(2009)415–418

([Bmim]Cl)was prepared according to the standard procedure fol-

lowed by repeated recrystallization from dry acetonitrile.The syn-

thesis of Bmim[FeCl4]has already been reported in the literature

[21,22]and was dried and degassed before use.P3MT nanospheres

were produced by simply adding the monomer to Bmim[FeCl4]as

a magnetic ionic liquid solvent.Typically,6mL of Bmim[FeCl4]

and2mL of monomer were mixed with stirring.The solution

was stirred for24h at room temperature,and then the polymer

was removed from the Bmim[FeCl4]solution by?ltering.The?l-

tered P3MT was dried for3h at60?C in a vacuum oven and

further puri?ed by methanol washing.Then,P3MT was dried in

a vacuum for48h at room temperature.In order to apply mag-

netic?eld to the polymerization process,two permanent magnets

were used.The glass cell containing Bmim[FeCl4]was sandwiched

by two fastened magnets in order to maintain the magnetic?eld

across the cell.With the same molar ratio of oxidant to monomer,

conventional solution polymerization were also carried out.The

monomer was added into an aqueous solution,then the FeCl3so-

lution was introduced into the solution with continuous stirring,

and the polymerization reaction proceeded.The obtained poly-

mers were washed with water and methanol to remove unreacted

chemicals.

2.2.Characterization

FTIR spectra of the composite nanospheres dispersed in KBr

disks were recorded on a Bio-Rad FTS135FTIR spectrophotome-

ter.Each spectrum was collected by accumulating64scans at a

resolution of4cm?1.Raman spectra were recorded by using a

microscopic confocal Raman spectrometer using a785nm laser

beam and a charge-coupled detector(CCD)with4cm?1reso-

lution.TGA was conducted on a Du Pont Thermal Analyst2100

system,equipped with a TGA2050thermogravimetric thermal an-

alyzer under a nitrogen stream with a heating rate of10?C/min.

Field emission scanning electron microscopy(FESEM)using a JEOL

JSM-6700F FESEM was made at an accelerating voltage of5kV.

The conductivity of the P3MT nanostructures was measured by the

conventional four-probe method.

3.Results and discussion

The nano?bers of conducting polymer have been synthesized in

the biphasic ionic liquid/water system[13].The use of ionic liquids

for the electrochemical synthesis of conducting polymer has also

been reported by several groups[17,23],and then IL is used ideal

media for the synthesis of conducting polymer.As shown in Fig.1,

the only difference between IL and MIL is that the anion of MIL is

FeCl?

4.For the preparation of the P3MT nanospheres,Bmim[FeCl4]

ionic liquid containing no additional dopants or oxidants was used.

Morphology studies of the P3MT nanospheres were carried out by applying SEM.As shown in Fig.2,the obtained nanospheres showed a uniform spherical shape and had an average parti-cle diameter of50–60nm without aggregation.Variation of re-action conditions such as concentration and reaction time did not affect the morphology of the generated conducting polymers. Bmim[FeCl4]solutions seemed to act as a template of liquid phase.IL is not only isotropic organic liquids composed entirely of ions,but it is also anisotropic conductors due to their self-

organized structures.The macroscopic orientation of

self-organized

Fig. 1.Molecular structure of1-butyl-3-methylimidazolium tetrachloroferrate, Bmim[FeCl4].monodomains in IL may be important in the enhancement of properties because the boundary in randomly oriented domains highly disturbs anisotropic transportation of charges and ions [24].The ionic liquid may result in the formation of uniform nanospheres with a relatively narrow size distribution con?ned to submicrometer-sized domains.Thus,the structure and properties of P3MT could be ascribed to the structure formation of these MIL molecules with partially oriented anisotropic liquid domain being mixed in isotropic liquids.The effect of external magnetic?eld was then studied.Fig.2b showed SEM image of P3MT

nanostructures

Fig.2.SEM images of P3MT nanospheres obtained in MIL(a)without magnetic?eld and(b)with magnetic?eld.(c)shows the corresponding size distributions in parti-cle as shown in(a).

S.Shang et al./Journal of Colloid and Interface Science333(2009)415–418

417

Fig.3.FTIR(a)and Raman(b)spectra of P3MT obtained in MIL.

synthesized in MIL with magnetic?eld.When polymerized with-out magnetic?eld(Fig.2a),spherical P3MT particles were formed as stated above.While interestingly,these nanoparticles seemed to be aligned under magnetic?eld.The morphology of P3MT changed to a network structure or bridged form of particles,and they were oriented with the direction of the applied magnetic?eld.Thus,the external magnetic?eld seems to affect these local structures and the?nal polymer structure.

Fig.3showed FTIR and Raman spectra of P3MT obtained in MIL.In the FTIR spectrum(Fig.3a),there were several inten-sity peaks present in the range of2800–3100cm?1,which can be attributed to the C–H stretching vibrations[25].The range of 600–1500cm?1was the?ngerprint region of the P3MT.The peak around1355cm?1may be ascribed to the methyl deformation of P3MT.The absorption bands associated with C=C/C–C stretching vibration occurred near around1582and1668cm?1,which may be considered to arise predominantly from both endocyclic and ex-ocyclic double bonds in the oxidized species of polyheterocyclics [26].

In the Raman spectrum of P3MT(Fig.3b),the most intense band at around1464cm?1corresponded to the symmetric C=C stretching deformation[27],while the intensity band at1375cm?

1

Fig.4.TGA curve of P3MT obtained in MIL.

was associated with C–C intraring stretching deformations in the aromatic thiophene ring[28].The band at1152cm?1was as-signed to the antisymmetric stretching vibration of C–C bonds[29], whereas another interesting band observed at1223cm?1in P3MT had been attributed to the interring C–C stretching[30].The bands ascribable to the C–H in-plane deformation vibration was observed at1048cm?1[31].The bands at748cm?1were related to C–S–C in-plane deformation[32].

To investigate the thermal stability of P3MT obtained in mag-netic ionic liquid,the thermal properties of P3MT were investi-gated,as shown in Fig.4.There were two evident decomposition processes during the thermal degradation of P3MT,and these two decomposition occurred at268and446?C,respectively.

The polymerization yield and conductivity of P3MT could be varied by the synthesis method.The yield in conventional solu-tion polymerization was about28.1%,while the MIL polymerization approach produced62.5%P3MT.The higher polymerization yield of the MIL system may be due to a high local concentration of the monomer in the IL,which accelerated P3MT growth in the IL. However,when MIL after the reaction was re-mixed with the new monomer,the yield was only about12%,much lower than that in the?rst run.It meant that MIL cannot be reused e?ciently as ox-idant again,but it still can be reused as solvent.The conductivity of P3MT obtained in MIL was about8.4S cm?1.In comparison,the conductivity of a similar sample prepared through a bulk solution synthesis method with FeCl3as the oxidant was about0.51S cm?1. In general,the conductivities of polymers are related with the synthetic methods,molecule size and structure,arrangement on molecule,kind of dopants and doping degree,etc.In the magnetic ionic liquid polymerization system,P3MT fabricated in MIL may have more attractive well-de?ned nanostructures,highly organized molecule and high doping degree for high conductivity.

4.Summary

A facile and convenient method to synthesize P3MT nano-spheres with their size ranging around50–60nm via polymeriza-tion of monomer in a magnetic ionic liquid without the additional dopant or oxidant was reported.The formation of the polymers was con?rmed by SEM,TGA,FTIR and Raman analysis.The yield and conductivity of these P3MT nanospheres obtained in MIL were better than those synthesized in conventional solution polymeriza-tions.Further investigations on effect of many factors,such as tem-perature,magnetic?eld and structures including the alkyl chain length of the cation,on the preparation and properties of P3MT are in progress.

418S.Shang et al./Journal of Colloid and Interface Science333(2009)415–418

Acknowledgments

The work is supported by the Hubei Province Educational Bu-reau and National Natural Science Foundation of China.

References

[1]A.Malinauskas,J.Malinauskiene,A.Ramanavicius,Nanotechnology16(2005)

R51.

[2]J.Lu,K.S.Moon,B.K.Kim,C.P.Wong,Polymer48(2007)1510.

[3]G.Sonmez,https://www.360docs.net/doc/fd11184360.html,mun.(2005)5251.

[4]R.H.Baughman,C.Cui,A.A.Zakhidov,Z.Iqbal,J.N.Barisci,G.M.Spinks,et al.,

Science284(1999)1340.

[5]C.A.Amarnath,S.Palaniappan,A.Puzari,P.Rannou, A.Pron,Mater.Lett.61

(2007)4204.

[6]A.N.Aleshin,Adv.Mater.18(2006)17.

[7]P.Leclere,M.Surin,P.Viville,https://www.360docs.net/doc/fd11184360.html,zzaroni,A.F.Kilbinger,O.Henze,et al.,Chem.

Mater.16(2004)4452.

[8]J.H.Burroughes,D.D.C.Bradley,A.R.Brown,R.N.Marks,K.Mackay,R.H.Friend,

P.L.Burn,A.B.Holmes,Nature347(1990)539.

[9]H.S.O.Chan,N.S.Choon,Prog.Polym.Sci.23(1998)1167.

[10]Y.Berdichevsky,Y.H.Lo,Adv.Mater.18(2006)122.

[11]L.Liang,J.Liu,C.F.Windisch,G.J.Exarhos,Y.H.Lin,Angew.Chem.114(2002)

3817.

[12]N.R.Chiou,C.Lu,J.Guan,L.J.Lee,A.J.Epstein,Nat.Nanotechnol.2(2007)354.

[13]T.Welton,Chem.Rev.99(1999)2071.[14]P.Wasserscheid,T.Welton,Ionic Liquids in Synthesis,Wiley–VCH,Weinheim,

Germany,2003.

[15]J.H.Davis,P.A.Fox,https://www.360docs.net/doc/fd11184360.html,mun.(2003)1209.

[16]W.Lu,B.R.Mattes,Synth.Met.152(2005)53.

[17]S.Ahmad,M.Deepa,S.Singh,Langmuir23(2007)11430.

[18]K.Wagner,J.M.Pringle,S.B.Hall,M.Forsyth, D.R.MacFarlane, D.L.O?cer,

Synth.Met.153(2005)257.

[19]P.Kubisa,J.Polym.Sci.Polym.Chem.43(2005)4675.

[20]J.M.Pringle,O.Ngamna,C.Lynam,G.G.Wallace,M.Forsyth,D.R.MacFarlane,

Macromolecules40(2007)2702.

[21]M.S.Sitze,E.R.Schreiter,E.V.Patterson,R.G.Freeman,Inorg.Chem.40(2001)

2298.

[22]J.Y.Kim,J.T.Kim,E.A.Song,Y.K.Min,H.Hamaguchi,Macromolecules41(2008)

2886.

[23]H.Randriamahazaka, C.Plesse, D.Teyssie, C.Chevrot,Electrochim.Acta50

(2005)4222.

[24]C.M.Gordon,J.D.Holbrey,A.R.Kennedy,K.R.Seddon,J.Mater.Chem.8(1998)

2627.

[25]Y.D.Wang,M.F.Rubner,Synth.Met.39(1990)153.

[26]R.G.Davidson,T.G.Turner,Synth.Met.72(1995)121.

[27]J.Casado,V.Hernandez,Y.Kanemitsu,J.T.L.Navarrete,J.Raman Spectrosc.31

(2000)565.

[28]B.Dufour,P.Rannou,J.P.Travers,A.Pron,M.Zagorska,G.Korc,I.Kulszewicz-

Bajer,S.Quillard,S.Lefrant,Macromolecules35(2002)6112.

[29]F.Chen,G.Q.Shi,J.X.Zhang,M.X.Fu,Thin Solid Films424(2003)283.

[30]E.A.Bazzaoui,J.P.Marsault,S.Aeiyach,https://www.360docs.net/doc/fd11184360.html,caze,Synth.Met.66(1994)217.

[31]E.F.Steigmeir,H.Auderset,W.Kobel,D.Baeriswyl,Synth.Met.18(1987)219.

[32]G.Louarn,J.P.Buisson,S.Lefrant,D.Fichon,J.Phys.Chem.99(1995)11399.