天然纤维素的核磁共振碳谱表征

Characterization of native cellulose using solid-state ^(13)C-CP/MAS NMR spectroscopy

利用核磁共振碳谱(NMR)和X衍射研究几种常见的天然纤维素纤维(苎麻、亚麻、棉纤维)以及2种浆粕(竹浆和硬木浆)的结晶结构,并探究2种方法之间的差异。详细解析这些纤维素纤维的核磁共振碳谱,一些结构特征参数如结晶度、侧向微纤尺寸以及晶型的组成被确定。利用核磁共振计算的几种纤维素的结晶度和晶粒尺寸比利用X衍射计算的要小,只有对于高结晶的纤维素样品如苎麻和亚麻偏差才比较小,认为主要原因在于NMR结晶区信号峰的强度只反映结晶相内部的C原子数目,而没有反映晶区表面C原子的数目。

everal common native cellulose,ramie,flax,cotton,as well as bamboo pulp and hardwood pulp were investigated using ^13C-CP/MAS NMR spectroscopy and X-ray diffraction,and the differences between two methods were discussed.NMR spectra of these fibers were analyzed in detail and some structure parameters such as crystallinity,lateral microfibril size,and allomorphs content were determined.Crystallinity and crystalline size calculated by NMR method are less than these obtained by X-ray diffraction.The reason is that the intensity of crystalline signal depends on the number of carbon atoms presented within crystallite in ^13C NMR spectra.