Mechanochemical Synthesis and Characterization of Polyaniline Catalyzed by Maghnite-H

Conductive polymers had been the topic of the large number of investigations during last decades because of their unique properties such as mechanochemical strength, electrical conductivity, corrosion and thermal stability. Maghnite-H+ is a montmorillonite sheet silicate clay, which exchanged with protons. Polyaniline (PANI), with unique electrical and optical properties, is a promising candidate for wide range of potential applications. So that, in the present paper we report: i. Synthesis of Polyaniline by chemical polymerization of aniline using montmorillonite (Mag-H + ) as Protonic source. ii. Different oxidant such as (K2S2O8 , K2Cr2O7 , CuCl2). iii. Characterization of different Polyaniline by different technics. With these easy synthesis associated good solubility, thermal stability and high electrical conductivity.


Introduction
In the recent year, polyaniline composite and nanocomposite suggest a great importance in the present nanotechnology, due to its easy synthesis , low cost environmentally stability and high conductivity 1 . These properties optical and electrical of polyaniline widen his application in several estate such as electronics devices (organo semi conductors, transistors), batteries and combustible piles. In many articles, preparation of polyaniline (PANI) soluble has been subjected 2 , this very day, polymerization of aniline in montmorillonite (layered solid) by chemical methods have been reported 3 . The solubilization 4 of polyaniline is important parameter for studding, this physical properties depend on the route of the synthesis of polymer. Generally speak this parameter solubility after synthesis of polyaniline by oxidative polymerization of aniline in aqueous medium with ammonium persulfate (APS) solution and doping by different protonic acid such as (DBSA, CSA) 5 . Here we report a facile chemical method to high quality and solubility of polyaniline under the normal condition using mixture of (montmorillonite/oxidant), when oxidant (K 2 S 2 O 8 , K 2 Cr 2 O 7 , CuCl 2 ) is solid and water at low temperature. Another important parameter influencing the properties of the resulting polymer organo soluble hybrid (organic-inorganic) is the monomer, the catalyst and the molar ratio (oxidant/monomer) = 0,58. This dissertation describes chemical synthesis of novel composite material based a montmorillonite, oxidant soluble in various organic solvents. By TGA and under the moisture and protonic source (Mag-H + ), the weight percentage of PANI Should have been round 38,83% at 600 0 C, and we obtained 6,65 % of aniline repeating units in 1 Molecule of PANI. By UV-vis spectra, on taking the soluble PANI in various solvents, we can calculate the band of energy by this equation.
The solubility parameter (δ) is usually expressed in (cal/ cm -3 ) 1/2 or preferably (j/cm -3 ) 1/2 units for many compound is defined from Hildebrand-Scotchard Solution theory is: In 1 H-NMR spectra, the peak (-NH-) appear at 4, 81ppm in different oxidant for EB-form PANI but not appear in ESform Because it's protened form. The resulting organo soluble polyaniline (PANI-Mag) has been characterized by various physico-chemicals technics.
The best yield was obtained using "Maghnite-H + 0.25M", so for this reason this sample was used to study the effects of catalyst on polymerization. Acid treatment of "Raw-Maghnite" causes a reduction in octahedral content (Al 2 O 3 ) and resulted in an increase in the proportion of silica (SiO 2 ) observed.
5,1 ml of (0.055 mol) aniline was added to 6% of (0.356 g) Mag-H + clay catalyst layered. The reaction was stirring for 30 mn at 0ºC, after this time 3g of (0.013mol) oxidant was added slowly during 10 mn, after this we added drop by drop 15 ml of water. The reaction was continued for 1h 30 mn in the optimal condition (0ºC). The precipitate product was filtered and washed with distilled water as far as neutralization, because this product contained traces of initiator, oligomer and monomer. In the end, we obtained black solid which be composed of (polymer-Mag

Results and Discussion
Polymerization and Product Characterization: The results of polymerization experiments of 0.055 mol aniline with 1.5% of oxidant (K 2 S 2 O 8 ﴿ induced by 6% of catalyst "Maghnite-H + 0.25M" are reported. For all these experiments the temperature was kept constant at 0°C for 3hours.

FTIR spectral analysis:
The FTIR spectra of the PANI-ES and PANI-EB under the same conditions were shown in figure-1 and figure-2. It was found that PANI had characteristic peaks at around 3631 cm −1 and 3288 cm −1 due to the characteristic free N-H stretching vibration suggests the presence of primary and secondary amino group (-NH-and -NH 2 ), 1557 cm −1 , 1501cm −1 (C-C stretching deformation of quinoide and benzenoide ring respectively), 1293 cm −1 (C-N stretching of secondary aromatic amine), 1168 cm −1 and 838 cm −1 (out-ofplane deformation of C-H in the 1,4-disubstituted benzene ring), which was similar with that of PANI sample without HCl under the same conditions. All of these peaks were identical to those of PANI synthesized by a common method 9 . UV spectral analysis: Conductive polymers have a conjugated system of double bonds in a backbone polymer. These polymers show some conventional transitions in the UV region, such as n →π * and π →π * . The π → π * transitions of conjugated double bonds are close to the visible region, associated with polaron and bipolaron states as well as solution conductive polymers 11 . The UV-visible spectral peak in the 250-300nm region is due to the aniline groups and π →π * is a conjugated couple system of the benzoic states in the 350-400 nm regions.       In the present study, the PANI-Mag composite was prepared with K 2 S 2 O 8 as the oxidant, aniline as monomer and Mag-H + as a catalyst; the relation between the content of catalyst and the conductivity was investigated. As shown in table-3, the conductivity of the polymer is largest when ratio of oxidant/monomer = 0,58 and increases significantly with the addition of content of catalyst, the dc conductivity of PANI-Mag composite measured through a two probe method is 3.9 10 -4 S/cm, same method shows conductivity in the range 10 -6 only 15 , which proves the superiority of present method. Thermal Analysis: The thermogravimetry analysis and differential thermal analysis performed in the polyaniline; show the thermal stability of the polymer; the thermogram presented in the figure-7. Give the weight percentage of polyaniline determined in relation to temperature. First there is a low mass loss of less than 8.55% between 186.53°C and 252.51°C; resulted from the evaporation of moisture by cons there is significant drop in mass of about 19.61% between 390.16°C and 487.92°C, the main mass loss is associated with degradation of polymer 16 . Therefore, the weight percentage of PANI should have been around 38.83 % of initial mass is conserved. The residual mass is associated with the presence of polyaniline reticule, which is formed at high temperatures 17 .  [18][19] in the polymerization of epichlorhydrin, propylene oxide and cyclohexene oxide by Mag-H+ and the polymerization of styrene by montmorillonite, respectively. This phenomenon is probably the result of the number of initiating active sites responsible of inducing polymerization; this number is prorating to the catalyst amount used in reaction. the effect of temperature on polymerization was studied. The results are shown in figure-9. The yield of polyaniline was found to increase with the temperature the temperature. The rate of polymerization at 0°C, however, was the small. A similar effect was shown in the polymerization of aniline initiated by chlorhydric acid 20 . Conclusion PANI/clay composite and nanocomposite were prepared using Mag-H + (eco-catalyst Algerian) and K 2 S 2 O 8 as the oxidant, various analytical techniques prove the formation of conducting PANI-ES (éméraldine salt phase of the polymer). The FTIR spectroscopy evidence the formation of polyaniline structure containing 1, 4-para-disubstituted linear chain, The 1 H-NMR spectroscopy evidence the (-NH-and -NH 2 ) end group respectively, UV-Visible spectra revealed the absorption peaks due to π-π* transition of polyaniline, The results of differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA) showed the improved thermal stability of the materials. Based on solubility studies, the composite is soluble in conventional organic solvents. Besides, this composite can be used as coating or molding material in many uses such as in anticorrosion protections, antistatic applications and photovoltaic cells.