In this study, composite of polyaniline containing Fe2O3 and CoO with nanometer size was synthesized by a chemical method using hydroxyl-propylcellulose as a surfactant. The characteristics of products such as morphology and conductivity were studied. The results indicate that, the morphology and conductivity of product are dependent on the surfactant, the type and concentration of metallic oxide

HAMID REZA KHORSHIDI

HOSSEIN EISAZADEH

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Journal of Engineering Science and Technology Vol. 3, No. 2 (2008) 146 - 152 © School of Engineering, Taylor’s University College   146 PRODUCTION OF POLYANILINE COMPOSITE CONTAINING Fe2O3 AND CoO WITH NANOMETER SIZE USING HYDROXYPROPYLCELLULOSE AS A SURFACTANT HOSSEIN EISAZADEH*, HAMID REZA KHORSHIDI Faculty of Chemical Engineering, Babol Noshirvani University of Technology,      P.O.Box 484, Babol, Iran *Corresponding Author: Eisazadeh@hotmail.com           Abstract In  this  study,  composite  of  polyaniline  containing  Fe2O3  and  CoO  with nanometer  size  was  synthesized  by  a  chemical  method  using  hydroxyl propylcellulose  as  a  surfactant.  The  characteristics  of  products  such  as morphology  and  conductivity  were  studied.  The  results  indicate  that,  the morphology and conductivity of product are dependent on the surfactant, the type and concentration of metallic oxide. Keywords: Composite, surfactant, metallic oxide, morphology, conductivity   1. Introduction Polymers are generally used in a wide range of applications often for their low cost, light weight and mechanical properties, or for the three characteristics combined. One of the main characteristics required for electrical and/or optical activities to occur in a polymer is a conjugated backbone which can be subject to oxidation or reduction by electron acceptors or donors. Due to delocalization of the π electrons in conjugated polymers, chain rigidity is very often a predominant property and, as a result of this, an aggregated character of the chains is typical in such material. This results in intractability which has been one of the drawbacks in the field. Polyaniline  (PAn)  is  unique  among  the  conducting  polymers  in  that  it possesses excellent electrical, magnetic and optical properties. Because of its low cost as raw material it is generally regarded as one of the conducting polymers with very high potential in commercial applications. The insolubility in common solvents and infusibility of conducting polymers, in general, make them poorly processable either by solution technique or by melt processing methods [1, 2]. Production of Polyaniline Composite Containing Fe2O3 and CoO      147     Journal of Engineering Science and Technology         AUGUST 2008, Vol. 3(2)  Improvement of these material properties can be achieved either by forming composites of aniline, or by forming PAn composites or blends with commer cially available polymers or inorganic materials which offer better mechanical and optical properties, stability and processability [3 6]. A  wide  range  of  possible  applications  have  been  proposed  for  conducting polymers  such  as  conductive  paint  [7],  optical  devices  [8],  membrane  [9], biomedical applications [10], and removal of heavy metals [11,12] etc. In this study, polyaniline composite was prepared in the aqueous solution using KIO3 as an oxidant in the presence of metallic oxides such as Fe2O3 and CoO as additives, and hydroxypropylcellulose as a surfactant.  2. Experimental 2.1. Instrumentation A magnetic mixer model MK20, digital scale model FR200, scanning electron microscope (SEM) model XL30 were employed. The four point probe method was used to measure the volume resistivity of conducting polymer films.  2.2. Reagents and standard solutions  Materials  used  in  this  work  were  aniline  and  hydroxypropylcellulose  (HPC, Mw=106) from Aldrich, sulfuric acid, potassium iodate from Merck. All reagents were  used  as  received  without  further  purification,  unless  stated  otherwise. Distilled deionized water was used throughout this work. Aniline was purified by simple distillation. 2.3. Preparation of nanometer-size Fe2O3 A 10 g of FeSO4,7H2O was dissolved in 200 mL strong alkaline solution (pH=13 14)  at  60°C.  The  FeSO4  solution  was  hydrolyzed  and  after  30  minutes  the sedimentation was filtered and then dissolved in 1M sulfuric acid. Then the strong alkaline  solution  (pH=13 14)  was  added  to  the  resultant  acid  solution.  The products was filtered and dried at room temperature. 2.4. Preparation of nanometer-size CoO A 10 g CoCl2,6H2O was dissolved in 200 mL strong alkaline solution (pH=13 14) at 60°C. The CoCl2 solution was hydrolyzed and after 30 minutes the resultant sedimentation was filtered and dried at room temperature. 2.5. Preparation of polyaniline composite The reaction was carried out in aqueous media at room temperature for 20 hours. In  a  typical  experiment  1  mL  aniline  monomer  was  added to  stirred  aqueous solution of 100 mL of 1M sulfuric acid containing 0.8 g of KIO3, 0.5 g surfactant (HPC)  and  0.1 0.5  g  metallic  oxide  respectively.  After  20  hours  polymer composite was filtered. To separate the oligomers and impurities, the product was washed several times with deionized water and then dried at room temperature.  148       H. Eisazadeh and H. R. Khorshidi     Journal of Engineering Science and Technology         AUGUST 2008, Vol. 3(2)   3. Results and Discussion The chemical method can be a general and useful procedure to prepare conductive polymer  and  its  composites.  It  is  well  established  that  the  charge  transport properties of conjugated polymers strongly depend on the processing parameters [13]. Polyaniline (PAn) has a reactive N H group in a polymer chain flanked on either side  by a  phenylene ring, imparting a very high chemical flexibility.  It undergoes  protonation  and  deprotonation  in  addition  to  adsorption  through nitrogen,  which  having  alone  pair  of  electrons,  is  responsible  for  the technologically interesting chemistry and physics. The electrical  conductivity  of  various  composites  produced  under  different reaction conditions was measured on pressed pellets of the composite powders. The  average  thickness  of  the  compressed  pellets  was  250   m.  The  electrical conductivity of compressed pellets was measured using four point probe method. The results are shown in Table 1. As it can be seen the electrical conductivity is dependent  on  the  type  and  concentration  of  metallic  oxides,  because  the conductivity increases with increasing polarizability of the carrier solvents [14]. As PAn is molecular composite containing a cationic polymer backbone, dopant must  be  incorporated  for  maintenance  of  charge  neutrality.  As  a  result,  it  is expected  that  the  chemical  and  physical  properties  of  the  doped  PAn  will  be affected by dopant [15]. Also as shown in Table 1 the conductivity of products is related to the surfactant. The  morphology  of  composites  was  studied  using  scanning  electron microscope. As shown in Figs. 1 5, the size and homogeneity of particles are dependent on the type of metallic oxides and surfactant. This is presumably due to the  amount  of  adsorbed  chemically  surfactant  (grafting  copolymer)  to  the polyaniline  particles.  Surface  active  agents  affect  the  physical  and  chemical properties of the solutions. The type of surfactant is known to influence the rate of polymer formation, particle size, size distribution, morphology and homogeneity [16 21]. Adsorption of the surface active agent on the PAn particles is primarily due to the hydrophobic component in the surfactants, probably via a hydrogen bonding mechanism with the aniline N H group. As can be seen in Fig. 1, the polyaniline obtained using HPC exhibits spherical particles, because surfactants prevent from gross aggregation of particles. Figs. 2 and 4 show the morphology of pure Fe2O3 and CoO which have been prepared in this research. As shown in Figs. 3 and 5, the composites obtained using Fe2O3 and CoO as additives in the presence of HPC as a surfactant are composed of small spherical particles. As can be  seen,  the  type  of  additive  has  a  considerable  effect  on  the  size  and homogeneity of particles.  4. Conclusion In  this  work,  the  characteristics  of  PAn  composites  such  as  conductivity  and morphology  were  investigated  using  HPC  as  a  surfactant  in  the  presence  of nanometer size metallic oxides as additives. It was found that, the type of additive has  a  considerable  effect  on  the  conductivity  and  morphology  of  resultant products. The SEM micrographs show that the type  of metallic  oxide  plays a major role on the surface morphology of products. Also the surfactant decreases Production of Polyaniline Composite Containing Fe2O3 and CoO      149     Journal of Engineering Science and Technology         AUGUST 2008, Vol. 3(2)  the tendency to form agglomerate which leads to more homogeneous distribution in  the  particles,  because  the  surfactant  prevents  from  gross  aggregation  of particles. As shown in figures, the surfactant has a considerable effect on the size and  homogeneity  of  particles,  because  surfactant  adsorbed  chemically  to  the polyaniline (grafting copolymer).  Table 1. The Effect of Additive and Surfactant Type on the Conductivity of Polyaniline Composite. Type of sample  Concentration of oxidant (g/L) Concentration of Fe2O3 (g/L) Concentration of CoO (g/L) Concentration of HPC (g/L) Electrical conductivity (S/cm) Pure polyaniline  KIO3=8           4.5×10 6 Polyaniline and HPC  KIO3=8        5  1.2×10 8 Polyaniline and Fe2O3  KIO3=8  5        1.1×10 8 Polyaniline and Fe2O3 KIO3=8  1        6.8×10 6 Polyaniline + Fe2O3 + HPC KIO3=8  5     5  1.6×10 8 Polyaniline + Fe2O3 + HPC KIO3=8  1     5  1.2×10 8 Polyaniline and CoO  KIO3=8     5     1.2×10 8 Polyaniline + CoO + HPC KIO3=8     5  5  1.6×10 6 Polyaniline + CoO + HPC KIO3=8     1  5  0.7×10 8  Fig. 1. Scanning Electron Micrograph of PAn in an Aqueous Media Using HPC (Mw= 106, 5 g/L as a Surfactant). Reaction Conditions: (KIO3= 8 g/L, PAn Monomer= 10.7×10-2 mol/L, Volume of solution = 100 mL, Reaction time 20 hours at room temperature). 150       H. Eisazadeh and H. R. Khorshidi     Journal of Engineering Science and Technology         AUGUST 2008, Vol. 3(2)                                      Fig. 2. Scanning Electron Micrograph of Pure Fe2O3 (The method of preparation has been explained in the text). Fig. 3. Scanning Electron Micrograph of PAn and Fe2O3 Composite in an Aqueous Media Using HPC (Mw= 106, 5 g/L as a Surfactant). Reaction Conditions: (KIO3= 8 g/L, PAn Monomer= 10.7×10-2 mol/L, Fe2O3= 5 g/L, Volume of solution= 100 mL, Reaction time 20 hours at room temperature). Fig. 4. Scanning Electron Micrograph of Pure CoO (The method of preparation has been explained in the text). Production of Polyaniline Composite Containing Fe2O3 and CoO      151     Journal of Engineering Science and Technology         AUGUST 2008, Vol. 3(2)                     References 1.   Yin, W., Li, J., Li, Y., Wu, J. and Gu, T. (2001). Conducting composite film based on polypyrrole and crossliked cellulose. J. Appl. Polym. Sci., 80(9), 1368 1373. 2.   Machado, J. 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PRODUCTION OF POLYANILINE COMPOSITE CONTAINING Fe2O3 AND CoO WITH NANOMETER SIZE USING HYDROXYPROPYLCELLULOSE AS A SURFACTANT

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