I synthesize the emeraline base polyaniline according to Macdiarmid and keep it in a glass vessel for a long time. But now I see a different behavior. I guess maybe it was a environmental effect (especially moisture).
if moisture, you can easily detect it (run a drying test, determine percentage of volatiles, run elemental analysis before and after drying). EB will absorb only some moisture, but compared to emeraldine salt MUCH LESS (I do not remember how much EB absorbs, how many percent, but only a few; ES can absorb 10 ... 20% and more, depending upon which acid was used for doping)
moreover, please let us know what is the method you used for synthesizing EB (did you prepare PAni-HCl first, then you neutralized maybe using NH4OH?). If so, please run elemental analysis of a former (well behaving) EB lot and compare with the lot you have made now. Maybe the Cl ontent in your recent EB is different from what you had before? (maybe higher?)
Dear Wessling,
1- yes, I prepare PAni-HCl first, then neutralized using NH4OH.
2- unfortunately! I am not a chemist. I just synthesize and use it in my work. the observed difference in behavior related to photoresposibilty. That is a guess. because my parameters is very much in my work, I can just doubt about the problem.
3- I synthesize one time few month ago and have been work with the synthesized PAni. but now (after few month) I encounter with this problem and considering other parameters, I infer that some moisture maybe! inside my solutions.
then I just want to know that my PAni can absorb moisture? because I keep it in a closed glass vessel but in the environmental conditions.
I understand, but even though you are not a chemist: this is a chemical question first, and it does not help you if you follow just one hypothesis without analyzing; my strategy is always: run analysis and compare with possible hypotheses, then and only then make a conclusion what to do.
If you have problems running the analyses as I suggested, ask some chemist friend nearby to help you.
Now that you said you were just running the process as described not being a trained chemist, I assume something was different either in synthesis of PAni-HCl or in the neutralisation step.
possible deviations:
1) temperature history during synthesis of PAni-HCl (did you control the temperature, did you cool during synthesis?) - very important!
2) different effectiveness of neutralisation
3) different Cl content in neutral PAni (this is a very serious side reaction!)
4) one of the previous ones leading to different EB particles size in your dispersion of EB (did you ever check the particle size you had in your EB dispersion?)
I think, I could not express my problem correctly!
I synthesized the PAni 3-4 month ago and I have worked with it at this period of time. At the beginning, it had good results. But now I can see different behavior about that. I think it can be just a result of absorbing moisture then I proposed the question. Noting that I keep it in a environmental conditions.
ah, now I understand: you had made just one lot of PAni, ok. I assume you use the PAni-EB in form of dispersions. Absorbed water can be a reason, but not necessarily are the reason. Also particle size in the dispersion can be different.
There can be one more hypothesis: in case that the neutralisation by NH4OH was not 100% perfect, there will be residual HCl in the core of the EB. This could have been diffused to the outer shell of the particles changing the properties.
Therefore again I suggest to analyze, you should apply
- particle size determination of your dispersion
- elemental analysis
- UV-VIS spectrum of your dispersion
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