紫外光辐照聚乙烯醇的^1H NMR研究

A PROTON NMR STUDY OF PVA UNDER UV IRRADIATION

用1HNMR谱 ,自旋 晶格弛豫时间 (T1)和X 射线衍射研究了聚乙烯醇 (PVA)在紫外光 (UV)辐照后 -OH基团与溶剂中残余水质子间氢键的生成与质子交换 .结果表明随着UV光辐照时间的增长 ,水峰与 -OH质子峰逐渐相互靠近 ,同时水峰逐渐变宽 ,向低场方向移动 ,这与 -OH基团与溶剂DMSO中残余水的质子之间既有氢键生成又有质子交换有关 .对辐照前后的PVA的DMSO溶液进行变温氢谱的研究 ,表明随着温度的升高 ,二者的 -OH基团共振峰均逐渐变弱 ,溶剂残余水峰与 -OH基团峰逐渐移向高场 .PVA辐照前后随着浓度增大 ,羟基质子峰“变钝” .辐照后的PVA的X

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.