Abstract
An attempt was made to elucidate the dissolved state of polyacrylonitrile (PAN) in various solvents by analyzing 13C NMR chemical shift difference for the arbitrarily chosen two NMR peaks derived from PAN molecules and by considering solvent effect on the electro-magnetical parameters introduced previously with aid of solvation phenomena of PAN in solvents. For this purpose, R-PAN and γ-PAN employed hithetofore were subject to the analysis. Solvents employed included typical organic solvents such as dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), and aqueous (aq) inorganic solvents such as 70 wt% aq nitric acid (HNO3), 55 wt% aq sodium thiocyanate (NaSCN). The dissolved state or the solvation state of PAN in organic solvent was mainly discussed in comparison with that in aq HNO3, which is known most powerful solvent even for highly isotactic PAN. It was found that interaction of all solvents to polymer is strictly dependent on polymer stereoregularity and the solvent power is related to the solvent ability to interact on the long meso (m) sequence part in PAN. Aq HNO3 shows quite different interaction form with nitrile group in mm and mr (r, racemo) sequences rather without forming π electron conjugate system. In contrast to this, the organic solvents proved to have individually favorable interaction sites more or less forming π electron conjugate system with nitrile group in polymer. The favorable polymer site was mmr for DMSO and mr for DMF and DMAc. Solvation number of solvent was proved to be in good accordance with that theoretical solvation number, calculated by assuming that each solvent solvates on its favorable sites in polymer. The tentative solvation form for each solvent is proposed.
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Hattori, M., Yamazaki, H., Saito, M. et al. NMR Study on the Dissolved State of Polyacrylonitrile in Various Solvents. Polym J 28, 594–600 (1996). https://doi.org/10.1295/polymj.28.594
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DOI: https://doi.org/10.1295/polymj.28.594