How to measure the molecular weight of conducting polymer and what is common sovent for conducting polymer such as polypyrrole and polythiophene (both in dopped and undopped state), thanks!
If you are talking about polythiophene without any alkyl side-chains it is very difficult to dissolve beyond a certain molecular weight. But, if you do have alkyl side-chains such as poly(3-hexylthiophene) then it is soluble in chloroform and reasonably soluble in THF. Of course, the solubility is dependent on the molecular weight of the polymer you have. To measure the GPC, you can normally do it in THF with polystyrene as the standard. But, if the molecular weight is large enough that it is difficult to dissolve it, you can do either a GPC in chloroform or you can do a high temperature GPC with chlorobenzene or dichlorobenzene as the solvent. Again, this is applicable if you have alkyl side-chains that improve the solubility. NMR is a reasonable option if you have specific end groups. Again, the accuracy of molecular weight by NMR depends on the actual molecular weight of the polymer. If you have a high molecular weight then the accuracy of NMR integration goes down.
conducting polymer is difficult to dissolve. Contact Dupont company to see if they can provide GPC solvent for it. If there is end groups of polymer chains, NMR is helpful.
If you are talking about polythiophene without any alkyl side-chains it is very difficult to dissolve beyond a certain molecular weight. But, if you do have alkyl side-chains such as poly(3-hexylthiophene) then it is soluble in chloroform and reasonably soluble in THF. Of course, the solubility is dependent on the molecular weight of the polymer you have. To measure the GPC, you can normally do it in THF with polystyrene as the standard. But, if the molecular weight is large enough that it is difficult to dissolve it, you can do either a GPC in chloroform or you can do a high temperature GPC with chlorobenzene or dichlorobenzene as the solvent. Again, this is applicable if you have alkyl side-chains that improve the solubility. NMR is a reasonable option if you have specific end groups. Again, the accuracy of molecular weight by NMR depends on the actual molecular weight of the polymer. If you have a high molecular weight then the accuracy of NMR integration goes down.
if you are talking about a "conductive (or conducting) polymer", then you mean a conjugated polymer which is "doped" and after "doping" it is conductive, yes?
if yes, you can not use GPC because conductive polymers are not soluble, if you object to this statement, then please first read my publications (available here in RG) about solubility of conductive polymers, and then argue with me about the facts and data.
As Julien wrote, I think only MALDI-ToF can help.
As it was said MALDI-ToF can help. You may use solvent-free sample preparation method as in:
Anthony R Dolan, Troy D Wood, Analysis of polyaniline oligomers by laser desorption ionization and solventless MALDI, J. Am. Soc. Mass Spectr., 15 (6) (2004) 893–899
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