纤维素在ZnCl_2水溶液中的溶解性能及再生结构

比较了不同质量分数的ZnCl2水溶液溶解不同聚合度纤维素的能力,发现:质量分数为65.0%以下的ZnCl2水溶液不能溶解纤维素;当ZnCl2水溶液的质量分数达到或超过65.0%时,未被水分子饱和的Zn2+可与纤维素分子链作用,使纤维素溶解,且65.0%的ZnCl2水溶液的溶解效果最佳;随着纤维素聚合度的增大,其溶解性能下降;经ZnCl2水溶液溶解后的再生纤维素的聚合度下降.广角X-射线衍射(WAXD)分析表明再生纤维素为纤维素Ⅱ结晶变体;傅里叶变换红外光谱(FT-IR)显示ZnCl2水溶液是纤维素的非衍生化溶剂,且再生纤维素分子内的氢键减弱.

Solubility of Cellulose in ZnCl_2 Aqueous Solution and Structure of Regenerated Cellulose

The paper deals with the dissolving ability of ZnCl_2 aqueous solutions with various mass fractions for cellulose with different degrees of polymerization (DP). It is found out that (1) ZnCl_2 aqueous solutions cannot dissolve cellulose unless the salt mass fraction is higher than 65.0%;(2) when ZnCl_2 content is not less than 65.0%, the Zn~(2+) ions unsaturated by water molecules connect with the hydroxyl groups of cellulose, which makes the cellulose to dissolve;and (3) ZnCl_2 aqueous solution with a content of 65.0% is of the best dissolving ability for cellulose, and the ability decreases with the increase in DP. It is also indicated by WAXD results that the regenerated cellulose is the crystalline transformation of cellulose Ⅱ. Moreover, FT-IR results show that ZnCl_2 aqueous solution is a direct solvent for cellulose, and that the intramolecular hydrogen bond of regenerated cellulose weakens after the dissolution.