水在聚乙烯醇／水体系中的状态及氢键作用

The Water States in Poly(vinyl alcohol)/Water and Their H-Bonds

水在聚乙烯醇(PVA)中的状态直接影响PVA的热塑加工。采用DSC和Raman光谱研究了水含量对其在PVA中的状态及氢键作用的影响。结果表明:水在PVA中以3种状态存在,随水含量增加,非冻结合水比例减小,可冻结合水和自由水比例增加。通过高斯分峰可将Raman光谱水的羟基伸缩振动峰分为5种羟基振动峰叠加,分别代表多氢键结合水分子的羟基对称与反对称伸缩振动,双氢键结合水分子羟基伸缩振动,单氢键结合水分子羟基伸缩振动,无氢键或弱氢键相互作用水分子的羟基伸缩振动。水含量增加,单氢键结合与多氢键结合水分子含量增加,而双氢键结合与无氢键结合水分子含量减少。

The water states in poly （vinyl alcohol） （PVA） greatly affected the thermal processing of PVA. DSC and Raman spectroscopy were used to reveal the effect of water content on water states and H-bonds in modified PVA. The results showed that water molecules existed in PVA/Water systems as three states,and with the increase of water content,the ratio of nonfreezable bound water decreased,while the ratios of freezable bound water and free water increased. The Raman spectra of the hydroxyl stretching bands of PVA with different water contents could be deeonvolved to five peaks assigned to the OH stretching of symmetric and asymmetric multiple, bifurcated, linear and isolated H-bonded water molecules, respectively. As water content increased, the ratios of multiple and linear H-bonded water increased, while those of bifurcated and isolated H-bonded water were decreased.