High Resolution Solid State 13C NMR Study of Poly(vinyl alcohol) Fibers with High Tenacity Spun from a Dimethyl Sulfoxide Solution or an Aqueous Solution.

CP/MAS13C NMR analyses of hydrogen bonding and the chain conformation in the crystalline and noncrystalline regions for poly(vinyl alcohol) films

“…Figure 1 shows CP/MAS 13 C NMR spectra for unannealed A‐PVA films prepared by using different solvents. The CH resonance line of each sample splits into three lines—lines I, II, and III—in the order of decreasing chemical shift, in accord with the previous reports 8–13, 16. Here, it is newly found that the relative intensity of the CH triplet of the sample prepared from the aqueous solution significantly differs from that for the sample prepared from DMSO or HFIP solution.…”

“…When the substituent effect19, 20 of OH groups is assumed to be the cause of the split of the CH resonance line, such change in relative intensity of lines I, II, and III should not be interpreted in terms of this effect because the tacticity is the same for these samples. The appearance of the evident effect of casting solvents on the intensities additionally supports the previous assignment8–13, 16 that lines I, II, and III are ascribed to the CH carbons associated with the formation of two, one, and no intramolecular hydrogen bond(s) in the triad sequences. More detailed discussion about the intramolecular hydrogen bonding in the crystalline and noncrystalline regions is performed later.…”

“…CP/MAS 13 C NMR spectroscopy was also found to be very powerful in characterizing the intramolecular and intermolecular hydrogen bonds of PVA samples with different tacticities 8–12. In particular, the probability of the formation for the intramolecular or intermolecular hydrogen bonding in the meso sequence could be determined by statistical calculations based on the crystal structure models of PVA, and this parameter was found to well describe the features of differently treated PVA samples 11–13. Moreover, the conformation and hydrogen bonding for different frozen solutions of PVA were characterized in detail by statistical treatments for chemical shifts of the CH carbons and relative intensities of the resonance lines 14–16.…”

“…As for the noncrystalline region, this article is the first report to treat the detailed characterization by considering both effects of the conformation and intramolecular hydrogen bonding. The analysis made for the crystalline component is also much simplified compared to the previous method,10–13, 16 because we do not need to assume any crystal structure unlike the previous treatment. Through these analyses we evaluate the effects of solvents on the formation of hydrogen bonding in the solid state in relation to its formation in the frozen solution state.…”

Solid-State 13C NMR and 1H CRAMPS Investigations of the Hydration Process and Hydrogen Bonding for Poly(vinyl alcohol) Films

“…The same IIIr component was also directly observed in the crystalline component for the dried PVA fibers and the mole fraction was found to increase with increasing draw ratio. 28 The CH resonance line of the less mobile component obtained from eq 5 is shown in Figure 6b. Since the line shape is significantly different from that of the crystalline component, this resonance line is resolved into some constituent lines by the lineshape analysis 10 • 27 previously developed.…”