Study of the frozen water–poly(vinyl alcohol) system by 2H and 13C NMR spectroscopy

✍ Scribed by D. G. Gusev; V. I. Lozinsky; E. S. Vainerman; V. I. Bakhmutov

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 585 KB
• Volume: 28
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1260280717

✦ Synopsis

Abstract

^2^H and ^13^C NMR techniques were used to investigate the thermodynamic state of water molecules and of poly(vinyl alcohol) (PVA) chain segments in frozen 10% PVA solutions in 99.8% and 8.5% ^2^H~2~O in the ‐66 to 3°C temperature range. The minimum amount of water not entering into the structure of ice is shown to correspond to a ratio of three water molecules to four PVA hydroxyl groups. The quantity of unfrozen water in the investigated systems was observed to change in the 5‐6°C range next to the melting point of pure water. The measurements show that, within the same temperature interval, the temperature decrease is accompanied by a sharp decrease in the ^2^H spin‐lattice relaxation time T~1~, whereas ^13^C T~1~ and the width of the ^13^C NMR signals increase up until the resolved PVA signals disappear. The correlation time of the motion of water deuterons and the PVA chain segments was calculated from the ^2^H and ^13^C T~1~ data. The interrelation between the data obtained and the cryostructurization processes leading to the formation of gels in frozen aqueous PVA solutions is discussed.