HIGH-RESOLUTION SOLID-STATE C-13 NMR-STUDY OF POLY(VINYL ALCOHOL) FIBERS WITH HIGH TENACITY SPUN FROM A DIMETHYL-SULFOXIDE SOLUTION OR AN AQUEOUS-SOLUTION

The structure and hydrogen bonding of the crystalline and noncrystalline regions have been examined for poly(vinyl alcohol) (PVA) fibers with high tenacity by cross polarization/magic angle spinning (CP/MAS) C-13 NMR spectroscopy. The fibers were spun from a dimethyl sulfoxide (DMSO) or an aqueous solution, hereafter referred to as DMSO-fibers and aqueous-fibers. These are drawable up to 14 approximately 16 times at 225-degrees-C in an electric oven. The tensile strength and modulus attain to 20.6 g/d and 444 g/d for DMSO-fibers and to 13.6 g/d and 361 g/d for aqueous-fibers, respectively. CH resonance lines of CP/MAS C-13 spectra split into triplets for the crystalline and noncrystalline components of both sorts of fibers, indicating the formations of two, one, or no intramolecular hydrogen bond(s) in the triad sequences. These spectra have been resolved into three lines by a lineshape analysis and then the probability p(a) for the formation of the intramolecular hydrogen bonding has been determined by the method previously reported. The p(a) value for the noncrystalline component approaches one with increasing draw ratio for both sorts of fibers possibly due to the preferential formation of the intramolecular hydrogen bonding. In contrast, the p(a) value of the crystalline component stays almost constant for DMSO-fibers, whereas it increases with increasing draw ratio for aqueous-fibers. On the basis of these results, the structure and hydrogen bonding are discussed for the PVA fibers.