关键词: NMR, PVA,  , 氢键, 自旋-晶格弛豫时间(T₁), X-衍射

Abstract:

The hydrogen bonds formed and proton exchanging between the -OH groups of PVA under UV irradiation and the protons of residue water in DMSO solvent were studied by ¹H NMR, spin-lattice relaxation and X-ray diffraction. The results indicated that with the increase of UV irradiation time, the intensities of the polymer hydroxyl proton peaks decreased progressively and finally vanished. The linwidth the proton peak of the residual water in the solvent increased progressively with the increase of UV irradiation time, with simultaneous downfield shift of its resonance frequency. This was caused by the hydrogen bonds formed and proton exchanging between the polymer -OH groups and the residual water. In addition, DMSO solution of PVA was studied at different temperatures by ¹H NMR before and after UV radiation. The results showed that with the increase of temperature, the signal intensities of the hydroxyl protons from both the polymer and the residual water decreased, and the resonance frequencies shifted upfield. With the increase of PVA concentration, the hydroxyl proton peaks of PVA before and after irradiation became‘passivated’The data from X-ray diffraction showed that part of hydrogen bonds in PVA were broken after UV irradiation.

Key words: NMR, PVA, relaxation, hydrogen bond, X-ray diffraction