Dear Ramin,

The colour of PANI is pH dependent, as its protonated and non-protonated forms of the  have different spectral characteristics.  The colour changes from green (acidic solution) to blue (basic solution).

For doped polyaniline, or as you said in acidic condition, polyaniline exists in emerladine salt form, which is green in color. For undoped polyaniline, there exists three states, i.e. emerladine base, leucoemeraldine , pernigraniline, which are blue, yellow/white and purple in color respectively. Your question is not justified as in which state in three pH conditions.

Dear Ramin,

Based on PANI Synthesis: Polymerized from the aniline monomer, polyaniline can be found in one of three idealized oxidation states: leucoemeraldine (white/clear & colorless) emeraldine (green for the emeraldine salt, blue for the emeraldine base) and (per) nigraniline (blue/violet). Emeraldine base is regarded as the most useful form of polyaniline due to its high stability at room temperature and the fact that, upon doping with acid, the resulting emeraldine salt form of polyaniline is electrically conducting.

Thank you all

Dear Ramin,

The color of Pani is dark green in acid media anda blue color in basic media!

The color changes according with the oxidation degree (emeraldine, pernigraniline and leucoemeraldine) and dopping: salt or base.

My best

thanks man.

Polymerization in basic, neutral and weakly acidic

media gives brown powder with low conductivity.

References:

Oxidative Polymerization of Aniline:

Molecular Synthesis of Polyaniline and the Formation of Supramolecular Structures

I.Yu. Sapurina and M.A. Shishov

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/48758

Hi again, Dear Ramin

Due to the subjective appearance of Pani, the best is study it by spectrophotometric analysis. Following, some interesting papers:

Study of the interconversion of polyaniline oxidation states by optical absorption spectroscopy

A. MacDiarmid

doi:10.1016/j.synthmet.2004.05.019

Controlled interconversion of semiconducting and metallic forms of polyaniline nanofibers

A. MacDiarmid

doi:10.1016/j.synthmet.2004.09.038

My best, man!

Hi.thanks dear Professor

Hi! I'm trying perform a polyaniline and acrylamide copolymer but the resultant polymeric mass is brown instead green. Why? Can you help me, please? Thank you!

 Hi. Your reaction condition is alkaline and aniline Polymerization in basic, neutral and weakly acidic media gives brown powder with low conductivity.

References:

Oxidative Polymerization of Aniline:

Molecular Synthesis of Polyaniline and the Formation of Supramolecular Structures

I.Yu. Sapurina and M.A. Shishov

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/48758

green in acidic solution)

blue in basic solution

green black