it is not "solubility", these are just very fine colloidal particle dispersion, I ha checked all this; people simply do not look carefully enough, almost everybody is too quick with inappropriate terms.

you can easily check with particle size measurements, and follow my suggestions (rules) given in my papers, e.g. "solution or dispersion?", you can find in my RG page

any polar solvent such as DMF, NMP, DMSO

poly aniline is not good for electrospinning  alone, but you can synthesize  poly aniline nanofiber composite by accompany side polymer to main polymer solution

PAni synthesized with specific acids show solubility even in water.

Generally, NMP is preferred. 

sorry, you all did not search and read literature well (sorry to say so, but I thought everything is available for you via internet in your modern times now?)

Polyaniline, any conductive polymer is not soluble at; neither the doped, nor the undoped form.

for understanding and digesting this, please read the following:

https://www.researchgate.net/publication/253651172_Conductive_Polymers_as_Organic_Nanometals

or specifically 

https://www.researchgate.net/publication/202290125_Conductive_Polymer__Solvent_Systems_Solutions_or_Dispersions?ev=srch_pub&_sg=NIBVbZ4%2FfcVK3V8JJSza7hOipCyQC%2Fbx2vv3yPPg1AzCBEw8o6WNqPeN%2Ful9ghv6_zUuz3rBLSgTxWxGvvIrqJIjU8Gs1DWILk%2Fj9qLD2TAKjcDiMr5a%2FTB1kEqHSDPfn_nPK%2Bd70%2BIlCe4tHYl%2FN4jm76UHIGs2TKTe9z39LbuoD5MZoV5JmfDwqS%2FVs7i1IT

Chapter Conductive Polymers as Organic Nanometals

Article Conductive Polymer / Solvent Systems: Solutions or Dispersions?

Dear Seyed, I can not access these journals, if you have the articles please let us see a pdf copy.

I don't know whether you have looked at the publications which I have cited above, there I have given very clear theoretical and experimental proof that PAni can not be soluble and is not soluble, also I have described experiments which should be run if one wants to prove that PAni was truely dissolved.

I would assume that the papers you cited have not given particle size measurement results, nor did they crystallize PAni from their "solution". 

recently I came across some paper (draft) in which the authors claimed to have achieved recrystallisation. However, the microscopy (VIS spectrum), FTIR and especially elemental analysis of the crystals was not PAni! it was something else, unknown, but not PAni and not really conductive.

I tell you, it is not so easy to differentiate between true solutions and very good colloidal systems, it is hard work - but so far, all what I have seen is that PAni is insoluble, also the udoped form (the undoped form can be in colloidal systems with very small particles, like 5 nm!).

the best one is nmp.

The best solvent is NMP but in this solvent PANI changes its state from ES to EB. (by colour we can also assume green to blue)

please believe me (as long as you did not meausre by yourself): also NMP does not act as a "solvent" but as a *dispersant*. PAni is definitely insoluble! read my relevant paper, and if you disagree, send me your analysis results which bring you to the opinion that you got a true solution with NMP.

i strongly agree to sir Bernhard Wessling answer.

but the double doped (with DBSA+ sulfuric acid) pani salt show solubility, find the attachment.

it is not "solubility", these are just very fine colloidal particle dispersion, I ha checked all this; people simply do not look carefully enough, almost everybody is too quick with inappropriate terms.

you can easily check with particle size measurements, and follow my suggestions (rules) given in my papers, e.g. "solution or dispersion?", you can find in my RG page

Dear Prof Bernhard Wessling, 

Truly, I try to dissolve PANI, but I can't. 

But in literatures, there are a huge number of papers speak about electrospun polyaniline nanofibers, How? 

Thanks. 

if you prepare a good dispersion (= particle size below 100 nm, please study my publications!), then you can also electrospin! ALL of these papers which talk about "solution" in fact just had quite good dispersions! none of them had been solutions! (they simply only never analyzed using appropriate techniques!)

Dear Bernhard Wessling,

What method would you suggest to prepare a good dispersion of particles of emerladine salt doped with DBSA. I procured the doped formed of PANI (http://www.sigmaaldrich.com/catalog/product/aldrich/428329?lang=en®ion=US ) and I'm looking to create a good dispersion. I tried sonication and mixing in solvents? Are there any other methods?

the sigmaaldrich product is already doped, actually I don't know with what, probably HCl which is very bad. You should prepare your own PAni-DBSA. There are plenty of preparation methods in the lliterature.

You can use m-Cresol. m-Cresol (3-methylphenol) has the solubility of PANI within the range 2-10(%w/w) and shows conductivity of around 300 S/cm.

Gaurav Kumar, you did not read my previous answers, right?

It is not "solubility", these are just very fine colloidal particle dispersion, I had checked all this; people simply do not look carefully enough, almost everybody is too quick with inappropriate terms.

you can easily check with particle size measurements, and follow my suggestions (rules) given in my papers, e.g. "solution or dispersion?", you can find in my RG page

You can find it as a subchapter in here:

https://www.researchgate.net/publication/253651172_Conductive_Polymers_as_Organic_Nanometals

Chapter Conductive Polymers as Organic Nanometals

I strongly agree to answer of Wessling Sir.

Polyaniline is not soluble however it will make fine dispersions with NMP,DMF etc.

I have found NMP as best dispersant. You can use PTSA, CTAB or DBSA for PANI doping.

can i sonicate pani/NMP? and what method is better for it?

Dear Mahsa, Yes you can sonicate it simply pour NMP in beaker and sonicate it for some time after that add PANI and again soniate. 

TC

Chloroform

It seems I should repeat a comment which I added here some while ago:

Polyaniline, any conductive polymer is not soluble at; neither the doped, nor the undoped form.

for understanding and digesting this, please read the following:

https://www.researchgate.net/publication/253651172_Conductive_Polymers_as_Organic_Nanometals

or specifically 

https://www.researchgate.net/publication/202290125_Conductive_Polymer__Solvent_Systems_Solutions_or_Dispersions?ev=srch_pub&_sg=NIBVbZ4%2FfcVK3V8JJSza7hOipCyQC%2Fbx2vv3yPPg1AzCBEw8o6WNqPeN%2Ful9ghv6_zUuz3rBLSgTxWxGvvIrqJIjU8Gs1DWILk%2Fj9qLD2TAKjcDiMr5a%2FTB1kEqHSDPfn_nPK%2Bd70%2BIlCe4tHYl%2FN4jm76UHIGs2TKTe9z39LbuoD5MZoV5JmfDwqS%2FVs7i1IT

Also NMP does not dissolve PAni, but - if well done - can create a colloidal system, a nano-dispersion.

Chapter Conductive Polymers as Organic Nanometals

Article Conductive Polymer / Solvent Systems: Solutions or Dispersions?

Could anyone suggest ways of enhancing adhesion of PANi onto ITO coated PET substrates via spin-coating? I have dispersed PANi in NMP then used a 0.45 nm syringe filter before spin coating. I have tried different spin parameters: spin time and speed, but the PANi film just wont form on the ITO. There is just no adhesion of 'solution' onto the substrate. I'm also working on PANi/Si films and PANi film readily forms on Si substrates via spin coating. Any advice on PANi/ITO formation most welcome.

First, I suggest you to ask this as a separate question so you can get more answers specifically o your question.

Second, here is my advice: you need to clean the ITO first (degrease) and than activate by ozone or plasma

Noted Berhard, thanks

Pretreatment of the ITO with H2SO4 (try different concs) and avoid removal of the layer. This works for most polymers, eg. PE & PVC. This works very well. But I've never done this with ITO, as spin coating of PAni doped with CSA in m-cresol always worked fine. 

Can emeraldine base PANI can be dissolved in chloroform?

no, at best it can be dispersed.

You can see the following papers:

Conductive Polymers as Organic Nanometals

 https://www.researchgate.net/publication/253651172_Conductive_Polymers_as_Organic_Nanometals

Heating induced negative temperature coefficient effect in conductive graphene/polymer ternary nanocomposites with a segregated and double-percolated structure

https://www.researchgate.net/publication/318495904_Heating_induced_negative_temperature_coefficient_effect_in_conductive_graphenepolymer_ternary_nanocomposites_with_a_segregated_and_double-percolated_structure

Reduction of the heat capacity in low-temperature adsorption chillers using thermally conductive polymers as heat exchangers material

https://www.researchgate.net/publication/316910689_Reduction_of_the_heat_capacity_in_low-temperature_adsorption_chillers_using_thermally_conductive_polymers_as_heat_exchangers_material

Chapter Conductive Polymers as Organic Nanometals

Article Reduction of the heat capacity in low-temperature adsorption...

Article Heating induced negative temperature coefficient effect in c...

Can we use pure PANI for nano fiber through electrospinning ?

according to my viewpoint, you need a PAni dispersion in a suitable dispersion medium (solvent); pure PAni is a dry powder, can not be electrospun

dark green color indicate base or salt?

dark green indicates salt, you can look into this here:

Data PAni UV-VIS spectra

Please be aware of the fact that these are *dispersions* (nanoparticle dispersions, colloidal systems), NOT *solutions*

Try N-methyl pyrrolidone, NMP.

@ Jude Iroh: are you aware of the fact (which I had explained above again) that which solvent ever you try, the result (if any good one) will always be a dispersion and not a solution?

I wish to ask Bernhard Wessling after converting UV absorbance of the salt to the Tauc plot is it normal to get a band gap > 5 eV., as I know literature reports Eg between 2.5 to about 3.8 ( if I stand corrected). If this is possible what are the causes of having such a big band gap and hence what are the implications of this to the electrical properties of polyaniline salt?

@ Mariam K. Ali , sorry, I do not understand your question / comment completely. I am not familiar with " converting UV absorbance of the salt to the Tauc plot ", can you show me an example or a literature reference?

What I would like to comment is that UV (you wrote "UV") absorbance anyway does not tell you anything about band gap - that tells you something about UV absorbance, not about electron transfer band gaps.

for PAni, already post polymerisation treatment decides whether you have an insulator type of conductor or a metallic conductor.

@ Mariam K. Ali I suggest you start a new question - otherwise it will not be seen under the title of this Q&A thread

@ Mariam K. Ali please send me the link for your new question thread

@ Mariam K. Ali Generally, protonation of the emeraldine base causes a lattice distortion of polyaniline to form a polaronic lattice structure, which accounts for the shift to lower optical band gap (less than 4 eV). The characteristic absorptions of isolated quinoid imine units is ∼2.5 eV and benzene units is∼4.8 eV. In nutshell, as per the oxidation state of the PANI, the optical band gap may change. So in your case I wonder, whether you are talking about emeraldine salt. It resembles a highly reduced state , i.e., leucoemaraldine.

@ Mariam K I suggest you let us see the UV-Vis spectrum.

kindly find attached the spectra.. Bernhard Wessling

ah, I see - it is not a "UV" spectrum, but UV-Vis.

Here, you can compare it with "standard" spectra which we had prepared years ago: Data PAni UV-VIS spectra

that's why I said "UV spectra don't tell you anything about band gap", you see the band gap in the visible / NIR range.

@ Mariam K. Ali The NIR tells you how "metallic" in character is the PAni you have in hand. The spectrum above sows emeraldine salt "as delivered" - it is on the insulator side of the "insulator-to-metal transition". Here we described the IM transition: Article Dispersion-induced insulator-to-metal transition in polyaniline

sorry, I did not find the relevant UV-Vis spectra so quickly, maybe later. The peak at 800 nm is shifting towards 900 and higher, and will flatten (will not any more show a distinct peak) with more metallic property in electronic movement.

here it is:

Conference Paper Scientific and Technological Progress with Polyaniline and P...

on page 36, you can see a PAni spectrum where the PAni is fully metallic

m-cresol will produce a good PANI dispersion (solution-like).

Dear Sergio Mollá, PANI is in emeraldine salt or base state ?

Dear Prof. Bernhard Wessling, what is the possibility for dissolution of emeraldine base state of the PANI in NMP and DMF?

@ Mariam K. Ali, from your UV-ViS spectrum it seems like You have got emeraldine salt. Please check your Tauc's plot calculations. If you are getting the absorbance peak (benzenoid and quinoid) at around 330 and 420 your optical band gap should be in between 2.75 eV- 4 eV. So there is obviously a calculation error. Please refer to it.

@ Muhammad Aamir Shehzad As I have explained very often, also here in this Q&A thread, PAni (also emeraldine base) are not soluble at all. EB can very easily be *dispersed* in NMP or DMF, and although it "looks" like a solution, it is in fact a dispersion.

I suggest you read this: Data Can Conductive Polymers be truely soluble? or will they form...

or here: Chapter Conductive Polymers as Organic Nanometals

(in here, this is a subchapter)

Dear Bernhard Wessling, I have understood you point of view. Do you have any document visualizing the change in PANI shape after dedoping such as TEM or SEM images ?

I may have, but not easy to be found. Basically, the shape does not change. The "primary" particles both are 10 nm in diameter, globular in shape.

Only, what we had found, was that EB can be dispersed to even smaller particles, like 4 ... 5 nm in diameter. These are the building units also of the ES primary particles, but one can not isolate these when PAni is in ES status.

Thanks Dear, @Bernhard Wessling ... I agree with you.. So nice of you..

I am about to make EB powder to ES. do I disperse first in DMF before adding PTSA or how and what amount or concentrations do I use? do I need to filter after I disperse it in DMF or centrifuge? Bernhard Wessling any recommendation? I am not a chemist btw. Thanks

Jacob, I don't know what is the purpose of your work, but by doping EB powder you will not get a homogeneous doping result; maybe this is sufficient for your work, maybe not.

You can try your approach, first disperse EB in DMF (attention: a) please use only 1% EB maximum b) use some high shear dispersing device or a good ultrasound dispersing equipment), then you add some PTSA / water solution.

I assume the dispersion (original colour: blue) will flocculate and if somewhat successful, it will become green.

As I never used this approach, I would assume that you need some surplus compared to minimum PTSA amount, maybe at least 1 mol PTSA per 1 mol Aniline units in EB.

Thanks for your prompt response. I will try this. However, I am not sure what you mean by 1% EB. Also, the PANI EB we purchased had no molecular weight. How do I go about getting less than or equal to 1% EB? and is it a good idea to use two different dopants ? cos It hardly turns green with just ptsa but when Hcl is added it does?

with 1%, I mean you take 1 gram of EB powder into 100 g DMF.

for the molar ratio, you just take the molecular weight of aniline and calculate how many moles aniline you have in 1 g EB (in case you really take 1 g EB into 100 g DMF)

it is not a good idea to take different dopants, and HCl is the worst you can choose.

First, you have to make sure that EB is really well dispersed in DMF; then for doping with PTSA, you need to take some time, maybe even increase temperature

Bernhard Wessling sir, is that also similar to the functional PANI derivatives? I am working on modification of PANI. while i prepared PANI, it was not even soluble in the DMSO and NMP...but the modified one was easily solubilized in NMP...

Is there any ratio to dissolve or dispersed the PANI with organic solvents?

yes, same: also the functionalized PAni versions are insoluble, what you had made were dispersions (colloidal systems).

What you said " while i prepared PANI, it was not even soluble in the DMSO and NMP " means in reality: it was not *dispersible*. That is because you will have followed a wrong polymerisation procedure.

Hi Bernhard Wessling Sir when i used NMP solvent for making slurry it effect my film.can i use any water based solvent for PANI if yes which one?

water can only be used if you make PAni doped with PSSH (polymerisation in presence of PSSH); however, to my knowledge, only thin films, thin layers can be deposited then, no free-standing film (at least, I never tried and have never read); in addition, with PSSH as dopant, the conductivity is relatively low

Hi sir ????? in my work of poste graduate i synthesis PANI ( soluble in organic solvent ) wen i used (Algerian MMT) with out oxidizing agent (APS or PPS ).

you can see my work in research gate or my paper in polymer bulltin springer .

thank you

Abdelkader Rahmouni , whom did you address with "sir"?

and which paper did you mean we should read? (please just send the link on RG)

i have several paper in synthesis and characterization of PANI , i used heterogenous catalyst (Algerian MMT).you can synthesised PANI under effect of homogenous catalyst ( APS or PPS).

1-see research gate (Abdelkader rahmouni -Maghnite)

2-google scholar (Abdelkader rahmouni -Maghnite

3- polymer bulltin springer (Abdelkader rahmouni -Maghnite)

thank you?????

why you don't simply copy and paste the links?

because i am not at home??????????

It's simple, use google (abdelkader rahmouni-maghnite), you can find all my papers.

Tihomir Nikolaev Tsanov There can not be any solvent for PAni, due to principal reasons which I have laid down and experimentally as well as theoretically proven. Please read this:

Chapter Conductive Polymers as Organic Nanometals

sub-chapter 2 starting with page 525

I am trying to make films by drop-casting HCl-doped PAni dispersed in m-cresol on ITO and Si substrates, before heating them in the oven. Unfortunately, the resulting films are not homogeneous, i.e. the films resemble the shape of a liquid drying on a surface. They form an "X" shape that is thick at the center. Interestingly, the center part has Rq roughness of around 2 nm under AFM, very smooth.

What could be the reason why the films are not homogeneous? Thanks in advance.

Jan Rodriguez maybe you can send us a microscopy photo? (optical microscope)

and what was the particle size in m-cresol dispersion?

what concentration had you used?

(these questions are directed towards the hypothesis that your dispersion was sub-optimal)

Hi Prof. Bernhard Wessling , thanks for the reply. Attached here is an OM image of one of the films. I do not have information on the particle size in the dispersion. The concentration I used was 8 g/L. I filtered the dispersion using 0.22 um filter prior to drop-casting.

(part 1)

Thanks for sending your info and photo:

1. 8g/L looks ok

2. no info about particle size is not helpful, you should try to find a possibility to measure them; without such data, even if you once would be successful, you will not be able to achieve reproducible results, because each time you prepare a dispersion, you may end up with difefrent particle size ==> different properties

3. the OM photo is partially nice and helpful (see part 2 below), but I suggest to also use much higher magnification so to see whether you have agglomerates in your dispersion or not (the filtration through 0.22 µm filter was a good idea)

(part 2 to follow)

(part 2)

To me, the photo is indicating that you have an unpolar substrate (ITO, Si) surface. You should clean and activate the surface, e.g. using plasma.

By the way: I am not "Prof." :-)

Hi Dr. Bernhard Wessling (Sorry for the ignorance, addressing you as "Prof.")

Thanks a lot for taking your time to reply.

Regarding the substrates, I have tried several chemicals already to clean them but still get the same bad result. However, I have not yet tried to use plasma, I will let you know whether it worked or not.

I do not have access to DLS for now, or other methods of obtaining the particle size, but will surely try, once we get interesting preliminary results.

Thanks a lot for your insights, very helpful!

thanks and appreciated;

re "tried chemicals to clean" - did you try peroxides as well? (H2O2, other peroxides)

Hi Dr. Bernhard Wessling

I will consider trying peroxides in the future. Thanks

Using O2 plasma on the substrates did not help. Do you think that the powder is the problem? Is this a consequence of using HCl as dopant? I have read somewhere that you said HCl is the "worst" choice to dope PAni.

Unless we don't have information on particle size, it's hard to judge. I assume that your powder will not have been well dispersed.

It might help to add a little bit of surfactant (DBSA or else)

Stephen Rathinaraj Benjamin what question are you answering to, and what is the meaning of your answer? if you mean "DMF, DMSO are best 'solvents' for PAni" then you are wrong, because what you can achieve with PAni are never true solutions, but - if you do it well - good dispersions, colloidal systems.

Dear professor Bernhard Wessling i agree with your comments.

Mixture of DMF and DMSO (50/50/

M. Bouachrine what question are you answering to, and what is the meaning of your answer? if you mean "DMF / DMSO 50/50 are best 'solvents' for PAni" then you are wrong, because what you can achieve with PAni are never true solutions, but - if you do it well - good dispersions, colloidal systems.