I have synthesized the polymer that contain benzo[c][1,2,5]thiadiazole and 2-ethylhexyl thiophene-3-carboxylate. In order to apply in hydrogen evolution, i need to enhance its hydrophilicity. Polymer cant dissolve in methanol. I have tried several conditions. I choose NaOH (0.1M) as base, methanol, THF, methanol + THF, methanol + toluene as solvent respectively with 60~95 degree. According to the FTIR, the sodium group doesnt replace the 2-ethylhexyl group, in other words, the saponification reaction doesnt react. I need some advice to successfully saponify it, something like change the solvent or what. Or it just cant work?
Use a catalyst/self-catalyst, the stabilization of the intermediate entity is good enough to repel the saponification step!
Try catalytic transesterification. J. Otera, Chem. Rev. 1993, 93(4):1449–1470
You should be able to convert to the methyl or ethyl esters, which might be better behaved - and if they're still too hydrophobic and/or insoluble, they should be more easily saponified than the ethylhexyl ester.
have you not tried the acid hydrolysis instead? Maybe first obtaining the acid and, afer that, trying to neutralize to obtain the carboxylate could work.
Another option would be trying to use ohase transfer agent on your reaction mixture to promote at least a little solubilization for the saponification to start (TBAB might work).
I think that saponification cannot be done because this compound cannot be replaced by a proton due to its stability, meaning that its acidity is very weak, as we know that soap is the salt of fatty acid.
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