Hello everyone
i synthesized polyaniline sulfate using Ammonium persulfate and H2SO4. from the literature i know that the Pani salt should be green, my product is a very dark green, almost blackish green. should it be this dark?
( how much should i wash it after filtering , i used a lot of acetone and methanol but the filtrate was still slightly yellow/brown colored)
also i put a small amount of it in the oven to dry, seems like there was some moisture in the oven, so when i took it out the color was not green anymore it was like black with a slight dark blue tint to it, is it possible that it has converted to polyaniline base?
thanks in advance.
You perhaps overoxidized the Pani. It is important not to use more than 1:1 persulfate:aniline. The reaction solution should be green after the synthesis. However, when filtered and dried, it could become blackish green.
Dear Fa,
I agree with Waldemar, you probably produce pernigraniline which is dark-blue, or if reaction time is not sufficient or inapropriate concentrations of reactants- aniline oligomers.
Best way to produce polyaniline sulfate can be found:
J. Stejskal, R. G. Gilbert, Polyaniline. Preparation of a conducting polymer (IUPAC Technical Report), Pure Appl. Chem., 74 (5) (2002) 857–867.
Free download:
http://citeseerx.ist.psu.edu/viewdoc/download;jsessionid=561E4E79F6E22BDD7DF7E2FE90EB1D3D?doi=10.1.1.611.1175&rep=rep1&type=pdf
It seems to be pernigraniline state of the poly aniline (PANi), however better you repeat the reaction not more than the 1:1 ratio of per-sulfate :aniline combination and meanwhile wash with acetone and ethanol to remove any excess aniline and oligoanilines.
The synthesized PANI doped product can be really dark green. It depends on aniline-persulfate molar ratio,acid dopant, temperature of the polymerization and size of the particles. You have really good citation from Prof. Branimir N. Grgur on the PANI synthesis work. In this work you can find also a recommendation how to wash PANI. You can find also useful information in Macromolecules, 1998, 31 (9), pp 3007–3015_ Spectroscopic, Structural and Transport Properties of Conductive Polyaniline Processed from Fluorinated Alcohols, seminal works of MacDiarmid et al. etc.. It is important to use the acid-dopant (in your case -sulfuric acid ) solution for washing to save doping degree of the synthesized PANI.
thank you everyone for the answers , i really appreciate it.
i used a 1:1 molar ration of persulfate:aniline , also the polymerization was carried out at room temperature. i am not sure but my aniline might have impurities which caused this problem.
@ Professor Alexander Pud, so i should also wash the precipitate with sulfuric acid too?
thanks again
Yes, at the last stage. Besides, you can compare different PANI treatments by measuring PANI conductivity being a highly important criterion of doped PANI quality
The easy way to check if your synthesized PANI is over-oxidized, you should check the UV/visible spectrum of PANI dissolved in N-methyl-2-pyrrolidinone. The spectrum will reveal the type of PANI structure you synthesized.
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