Dear colleagues! Recently I tried to dissolve commercially available samples of PAN precursors (acrylonitrile-methyl acrylate-itaconic acid terpolymers) in water solutions of sodium thiocyanate for subsequent determination of IA carboxylic groups mass concentration. First ST water solution (with no polymer) had pH of appr. 8.8. Polymer were dissolved with no visible residue under stirring and slight heating. Second time I used other sodium thiocyanate, its water solution had PH of appr. 7.0, and when the same polymer sample were dissolved I saw a visible, very fine residue. When I tried to purify second ST by its crystallization in acetone, the same fine residue made acetone solution murky. I also tried to dissolve polymers in potassium thiocyanate water solution (pH of 9,5), but I saw the same fine residue. Had someone dealt with the same problem?
P.S. Thank you for any answers!
P.S.S Here is the file with IR spectra of "pure" ST (black line), old specimen of ST (blue line) and old ST that was crystallized in acetone and then dried under vacuum and slight heating (red line). First of them causes transparent polymer solution formation, other two lead to murky solution.
Dear Mikhail Sergeevich Balashov, why not doing simple analysis to know this white precipitates! Thé terpolymer you are dealing with is constitutes of two water unsoluble polymers, I think the precipitates is only fractions of the terpolymer where AN and MMA moities dominate the chain structure of these fractions. My Regards
Dear Mikhail Sergeevich Balashov, why not doing simple analysis to know this white precipitates! Thé terpolymer you are dealing with is constitutes of two water unsoluble polymers, I think the precipitates is only fractions of the terpolymer where AN and MMA moities dominate the chain structure of these fractions. My Regards
Dear Abdelkader BOUAZIZ, thank you for your answer! I thought about this, but it is quite strange that the first sample of the same terpolymer were dissolved without any residue (and as far as I know, hompolymer of PAN could be readily dissolved in NaSCN water solution). Next time I am going to find much ST of "pure" kind and dissolve polymer both in it and in "old" ST again. The residue is apparently too fine to be filtered (but I'll also check it), so I try to centrifuge it, washed and examine by all possible means.
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