DYNAMIC NUCLEAR-MAGNETIC-RESONANCE AND RAMAN-SPECTROSCOPIC MEASUREMENTS OF 5 KINDS OF N,N-DIMETHYLFORMAMIDE DERIVATIVES IN RELATION TO THE DISSOLUTION MECHANISM OF POLYACRYLONITRILE

The internal rotation of five kinds of N,N-dimethylformamide (DMF) der ivatives was studied by dynamic nuclear magnetic resonance (n.m.r.) an d Raman spectroscopic measurements in relation to the dissolution mech anism of polyacrylonitrile (PAN). The dissolution temperature (T-sol) of PAN was determined by the steric effect of the solvent molecules, i .e. the higher the bulkiness of a substituent, then the higher was the T-sol of PAN. The intermolecular interaction between the nitrile grou p and the solvents was evaluated by Raman spectra in terms of the larg e carbonyl shift (nu(c=o)). Dynamic H-1 n.m.r. spectroscopy measuremen ts revealed that the value of the coalescence temperature (T-c) was no t proportional to the steric factor, suggesting that the solvent prope rties are not determined solely by the latter and that internal rotati on of the solvent molecules is defined by the extent of looseness in t he packing of the solvent molecules in the liquid state. The significa nce of both intra- and intermolecular factors of the solvent molecules in the dissolution of PAN was also discussed. (C) 1996 Elsevier Scien ce Ltd.