DYNAMIC NUCLEAR-MAGNETIC-RESONANCE AND RAMAN-SPECTROSCOPIC MEASUREMENTS OF 5 KINDS OF N,N-DIMETHYLFORMAMIDE DERIVATIVES IN RELATION TO THE DISSOLUTION MECHANISM OF POLYACRYLONITRILE
M. Minagawa et al., DYNAMIC NUCLEAR-MAGNETIC-RESONANCE AND RAMAN-SPECTROSCOPIC MEASUREMENTS OF 5 KINDS OF N,N-DIMETHYLFORMAMIDE DERIVATIVES IN RELATION TO THE DISSOLUTION MECHANISM OF POLYACRYLONITRILE, Polymer, 37(12), 1996, pp. 2353-2358
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.