Can anyone please explain an effective in situ oxidative polymerization procedure for the synthesis of conductive Poly aniline nano composites based on Carbon nano tubes?
dear neeraj , I am also working on the same thing. I would like to prepare Nano fibers Composite from conducting polymers.
uniform dispersion of MWCNT'S into the electro spun Nano fiber is a trail and error procedure. I have found a constraint in this method : mixing of PANI and MWCNT'S. the ratio and the polymer concentration and average molecular weight will effect the resultant fiber morphology and overall fiber conductivity and fiber diameter too.
in general Nano fiber Composite can be done in three ways: 1) electro spinning technique and 2) casting technique 3) phase separation technique.
among all the electro spinning method is cost effective and easy method
Dear Gadipudi Murali, Thank you very much for your valuable suggestion.I will surely try electro spinning method.
how PANI can be doped ? select a suitable dopant, and select a suitable average molecular weight range of polymer monomer and solvent . polymerize the polymer by maintaining suitable temperature and sufficient time .
selection of solvent is necessary to make PANI /MWCNT'S composite smoother the electro spinning operation. dear neeraj, is it possible to coat PANI up to 100 micron thickness on stainless steel by electro deposition method?
Generally PANI can be doped in non redox manner.Organic acids such as CSA,TSA and in organic acids like HCl are found to be good dopants for PANI. 1M acid will be the best ochoice and the temperature needs to be low.In low temperature the prepared PANI will be in fiber form and the molecular weight will be higher.The measured DC conductivity will be higher in this case.
I heard about HCl is the worst dopant .HCl creates side reactions by forming some covalent bond somewhere (unknown where) in the PAni backbone. Moreover, HCl doped PAni is not thermally stable. The best dopant is para-toluene sulfonic acid.The PAni colour changes from undoped "EB" (blue) to doped "ES" (green).
We can also try the concept of secondary doping.Aniline monomers are polymerized in aqueous acidic medium of TSA. Then we can dedope it by 1M ammonium solution.Then we can apply 1 M CSA as secondary dopant.Then the compact coils of PANI gets extended and we can observe an increased conductivity.
Generally Poly aniline is insoluble in aqueous solutions.We can make it soluble by adding hydrophilic side groups like -OH,-COOH to the rigid polymer backbone.
for electro spinning of poly aniline :
take poly aniline and DBSA (acts as a protonating agent), and chloroform , N,N-Dimethyl formamide (DMF) are solvents for easier spinnability.
Various methods can be tested to prepare pani modified mwcnt. I donot know your requirement. Some people disperse mwcnt in SDS and then polymerize aniline in presence of oxidant like ammonium persulfate. Or you can functionalise cnt with aniline monomer first then use for polymerization reaction.
You may modify MWCNTs with a few aniline monomers and then initiated the polymerization in situ on the surface of MWCNTs. In this way, it is expected to derive well-dispersed and uniform composites.
Dear Pandian Kannaiyan,My aim is to develop a highly conductive film based on PANI-MWCNT nano composites.The main requirements are high DC as well as AC conductivity.
About polyaniline (PANI) solubility or solvents, you may see: L.W. Shacklette, C.C. Han, "Solubility and dispersion characteristics of polyaniline", Mat. Res. Soc. Symp. Proc., Vol. 328, 1993, 157; http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8104402&fulltextType=RA&fileId=S1946427400354070
Synthesis of Polyaniline Doped with Hydrochloric Acid (HCl):
Doped polyaniline (PANI-HCl) was chemically synthesized using aniline, previously distilled under vacuum, and ammonium persulfate ((NH4)2S2O8) as oxidant in a 4:1 monomer/oxidant molar ratio. 20 mL of the previously distilled aniline was dissolved in 40 mL of 1 mol per liter aqueous solution of hydrochloric acid in a 250 mL flask. During the dissolution the flask was kept inside a vessel containing a mixture of ice and salt at a temperature of ~ -10 °C. Separately, 12g of (NH4)2S2O8 was dissolved in 160 mL of 1 mol per liter hydrochloric acid aqueous solution. The acid solution of (NH4)2S2O8 was slowly and carefully added into the flask containing the aniline acid solution during a period of 2 h and under constant stirring. During this entire process, the reaction medium was kept in ~ -10 °C. The reaction medium changed color, going through tons of brown, blue and green, and a solid deposit was formed at the bottom of the reaction flask. The green sediment was filtered, rinsed with a 1 mol per liter HCl solution and dried under dynamic vacuum at room temperature for 72 h. Under these conditions the polymer obtained is in a doped state (PANI-HCl) slightly soluble in water.
Synthesis of Polyaniline Doped with Formic Acid (HCOOH):
Aniline was polymerized in formic acid (HCOOH) medium using (NH4)2S2O8 as oxidizing agent. In a typical procedure, 1 mL (0. 0107 mol) of previously distilled aniline was dissolved in 25 mL HCOOH (85% weight) at room temperature. The obtained solution was cooled to about 2 ºC in an ice bath. A solution of 2.44 g (0.0107 mol) (NH4)2S2O8 dissolved in 25 mL HCOOH (85% weight) was added drop wise into the cold aniline acid solution under constant stirring over a period of 30 min. The mixture was stirred over additional 2 h and its temperature was kept in 2 ºC during this period. At the end of this period of time a dark green solid was formed in the reaction medium. This solid was filtered, thoroughly rinsed with deionized water and methanol. Under these conditions the polymer is obtained in a doped state (PANI-HCOOH).
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