Structural and dynamical studies of poly(vinyl alcohol) gels by high-resolution solid-state 13C NMR spectroscopy

The C-13 CP/MAS NMR spectra of isotactic, syndiotactic and atactic poly(vinyl alcohol) (PVA) gels were measured in order to clarify the structure of the immobile component of PVA gel, In the C-13 CP/MAS NMR spectra, the three CH carbon peaks I, II and III (at about 77, 71 and 65 ppm) were clearly observed, which originate from the formation of strong intermolecular or intramolecular hydrogen bonds between hydroxyl groups like solid PVA. It has been assigned that these peaks originate from the crosslinked region in the gel stale. On the basis of the experimental results; intermolecular hydrogen bonds play an important role in the formation of the crosslinked-region in the gel state. Further, the effect of PVA's tacticity on the amount of the crosslinked regions by intermolecular interactions was discussed, In addition, molecular motion in the immobile and mobile region of PVA gel was discussed through the observation of C-13 spin-lattice relaxation time T-1. (C) 1998 Elsevier Science B.V.