CP/MAS 13C NMR analysis of the structure and hydrogen bonding of melt-crystallized poly(vinyl alcohol) films
CP/MAS 13C NMR analysis of the structure and hydrogen bonding of melt-crystallized poly(vinyl alcohol) films
复制标题
DOI：
10.1016/j.polymer.2006.01.082
复制
发表时间：
2006-03
期刊：
影响因子：
4.6
通讯作者：
Hu Yang;Shaohua Hu;F. Horii;Ryokei Endo;Hayashi Tetsushi
中科院分区：
文献类型：
--
作者：
Hu Yang;Shaohua Hu;F. Horii;Ryokei Endo;Hayashi Tetsushi
采用CP/MAS ~（13）C NMR谱对熔融结晶无规聚乙烯醇（A-PVA）薄膜的结构和氢键进行了表征。~（13）C自旋-晶格弛豫分析表明，PVA中存在三种不同T1 C值的组分，即结晶组分、移动的较少的非晶组分和移动的非晶组分，这与文献报道的不同PVA样品的结果雅阁。应该注意的是，熔融结晶膜的结晶和非结晶组分的T1 C值明显小于通过从水溶液浇铸制备的未退火和退火样品的那些。利用T1 C的差异分别记录了结晶组分和非结晶组分的~（13）C NMR谱，并用最小二乘曲线拟合成功地将它们的CH谱线分别分解为3条和7条组分谱线。此外，由此获得的组成线的积分强度的统计分析，能够确定的概率fafor形成分子内氢键的连续两个OH基团沿着每个链和另一个概率ft的反式构象的结晶和非结晶组分。研究发现，熔融结晶薄膜的fA值比未退火和退火样品的fA值大。在此基础上，讨论了熔体结晶过程中分子内和分子间氢键作用对结晶过程的影响，以及由此形成的结晶-非晶结构的特征。
The structure and hydrogen bonding of the melt-crystallized atactic poly(vinyl alcohol) (A-PVA) films, which were carefully prepared without significant thermal degradation, have been characterized by CP/MAS13C NMR spectroscopy. The13C spin–lattice relaxation analysis has revealed that there exist three components with different T1Cvalues, the crystalline, less mobile noncrystalline and mobile noncrystalline components, in good accord with the results for different PVA samples previously reported. It should be noted that the T1Cvalues of the crystalline and noncrystalline components are appreciably smaller for the melt-crystallized films than those for the un-annealed and annealed samples prepared by casting from the aqueous solution. The13C NMR spectra of the crystalline and noncrystalline components are separately recorded by using the difference in T1Cand their CH lines are successfully resolved into three and seven constituent lines by the least-squares curve fitting, respectively. Moreover, the statistical analysis of the integrated intensities of the constituent lines thus obtained enables to determine the probability fafor the formation of intramolecular hydrogen bonding in the successive two OH groups along each chain and another probability ftof the trans conformation for the crystalline and noncrystalline components. It is found that the favalue is relatively larger for the melt-crystallized films than those for the un-annealed and annealed samples. On the basis of these results, the features of the melt-crystallization and the resulting crystalline–noncrystalline structure are discussed by particularly considering effects of intra- and inter-molecular hydrogen bonding on the crystallization.