Solid-State 13C and 1H NMR Analyses of Hydrogen Bonding and the Conformation of Poly(vinyl alcohol) (FUNDAMENTAL MATERIAL PROPERTIES-Molecular Motion Analysis)

Abstract

CP/MAS 13C NMR analyses have been made for different frozen solutions of poly(vinyl alcohol) (PVA) samples with different tacticities. The CH resonance lines of the frozen PVA solutions split in different ways significantly depending on the tacticities and the solvents. These CH resonance lines are well resolved into 9 constituent lines whose chemical shifts are estimated by assuming the downfield shifts due to intramolecular hydrogen bonding and the upfield shifts induced by the g-gauche effect. Furthermore, the relative intensities of the lines for atactic PVA samples are successfully interpreted by the statistical treatment assuming the statistical formation of the intramolecular hydrogen bond and the random distribution of the trans and gauche conformations. Separate 1H CRAMPS analyses have also revealed the existence of the OH groups free from hydrogen bonding together with hydrogen-bonded OH groups in PVA films.