I have synthesized some conductive polymer. How we can improved their solubility?
thanks
I think polypyrrole is not soluble in any solvent.
Read this
https://www.researchgate.net/post/Which_solvent_should_we_use_to_solubilise_the_polypyrrole2
Frankly, it all depends on what exactly do you need to do with the polypyrrole (PPy). That is, if you need just a PPy film, I suggest electrochemical polymerisation as a method, with the film precipitating on the element you use as the electrode. I will (shamelessly) recommend my own work on the electrochemical polymerisation and monitoring of the growth of a 3-dodecylpyrrole film: Article Multielectrochromism of redox states of thin electropolymeri...
If structural modification of the monomer is acceptable, I would suggest either N-alkylpyrroles or 3-alkylpyrroles (a word of warning in this case, the monomers tend to be extremely prone to polymerisation in contact with air, even at room temperature). A 3,3,3-trifluoropropyl (or any longer alkyl terminated with the -CF3 group) is also an excellent solubilising group and the electron-withdraiwng substiutent actually seems to be stabilisng pyrrole-derived monomers.
Frankly, we have been trying to get the actual molecular weight (MW) for a few poly(3-hexylthiophene) derivatives, all of them soluble and got the following results:
1H/13C NMR: Calculations based on the ratio of the integral of terminal group signals to the integral of the polymer signals (attempted this with both the alkyl chain signals and thiophene ring signals) - using a rather high grade spectrometer (600 MHz 1H base) we got a MW value of roughly 12 000 g/mol with a +/- error of about 2 000 g/mol, due to the extremely weak signals of the terminal groups in relaiton to the signals of the polymer.
GPC: Without a polypyrrole reference material, whose MW is known, you can only compare the polymers on a "lower MW"/"higher MW" basis. Polystyrene reference materials tend to be excellent for polystyrene, but when used to callibrate poly(3-alkylpyrroles) or poly(3-alkylthiophenes), due to the rigid main chain, the obtained MW values are in sharp disagreement to results obtained using other techniques.
MALDI-TOF / LDI-TOF mass spectroscopy: AFAIR, can be performed for insoluble materials (see DOI: 10.1021/ac000372q) and I would recommend this technique to you. There are some issues with the choice of matrix (i.e. we have seen unreliable results for a P3HT in a, if I remember correctly, graphite matrix), but IMHO, it provides the most reliable results.
Actually, my colleague - Kinga Kępska
- is the person in our team who has the most experience dealing with MW determination of conducting polymers and would be able to assist you in far greater detail.
Conducting polymers are generally INSOLUBLE. At best you get a decent DISPERSION
@Ahsan Nazir: Did you try dissolving the 3-hexylthiophene-pyrrole copolymer in chloroform? For pristine p3HT we achieved concentrations in excess of 1mg/ml, so a "solubility" on the order of 0.1mg/ml should be feasible. What was the expected p3HT content of your copolymer?
The poor solubility of conjugated heterocyclic polymers stems from several factors:
1) Lack of strong interactions with most solvents in the case of unsubstituted polyheterocycles and formation of heteroatom - hydrogen bonds (in some cases), promoting intermolecular attraction,
2) Interactions between the pi orbitals of conjugated ring systems (so called pi-stacking effect), further exacerbated by the flat nature of the conjugated bond system (i.e. lack of steric hindrance for forming aggregates with close-lying polymer chain segments, both intra-chain and inter-chain),
The general approach is to substitute conjugated systems with solubilising groups, that promote solvent-solute interactions (i.e. alkyl and CF3-terminated alkyl chains) or act as steric hindrance ("spacers", preventing/hindering pi-stacking).
@Ruediger Schweiss: Actually, I agree.
That said, the "conjugated polymer dispersion vs solution" debate is not a straightforward matter and for one not strongly involved in the subject might not be particularly relevant.
If I may offer some advice, a brief explanation of the thermodynamic difference between a solution and a dispersion would be far more convincing than a brief statement. This is particularly so when we see authorities in the field using the term 'soluble' in regards to conjugated polymers rather than 'dispersable' (sample DOIs enclosed below) and "newcomers" to the field may not be aware of the simplification involved.
DOIs:
10.1021/ja061274a
10.1073/pnas.162375999
10.1038/357477a0
10.1021/cr050149z
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