Sj. Varner et al., CHARACTERIZATION OF POLYIMIDES BY C-13 AND H-1 SOLID-STATE NUCLEAR-MAGNETIC-RESONANCE, Solid state nuclear magnetic resonance, 12(2-3), 1998, pp. 71-85
The polyimides LaRC-TPI, LaRC-IA and LaRC-SI and related model compoun
ds were investigated using C-13 and H-1 nuclear magnetic resonance (NM
R). Magic angle spinning was used to acquire C-13 isotropic chemical s
hift spectra of these materials. The spectra were assigned as complete
ly as possible. In addition, the principal components of some shieldin
g tensors were measured using variable angle correlation spectroscopy
(VACSY). Of those studied, LaRC-SI is the only polymer that is soluble
. However, after it is heated past its glass transition temperature, L
aRC-SI becomes insoluble. Experiments were performed in an attempt to
identify causes of this behavior. When magnetization from nuclei in ri
gid regions of the polymer is suppressed, the H-1 and C-13 NMR spectra
off soluble LaRC-SI are significantly different from those of insolub
le LaRC-SI. Hydration studies of LaRC-SI show that absorbed water plas
ticizes the polymer. (C) 1998 Elsevier Science B.V. All rights reserve
d.