纤维素在氢氧化锂/尿素水介质中的溶液性质研究(英文)

Solution studies of cellulose in LiOH/urea aqueous solution

纤维素可以在氢氧化锂/尿素的混合水介质中溶解.选取三种不同分子量的纤维素,在N,N-二甲基乙酰胺/氯化锂体系中进行溶解,并通过粘度法,准确确定其分子量.而后,在4.2%氢氧化锂与12%尿素的水介质中溶解它们.通过粘度法测定其特性参数,得到该溶液体系的M-H方程:[η]=1.695×10-3M0η.914(mL.g-1).并测定了体系的ML和q值分别为387.5 nm-1和6.1 nm,显示纤维素在该溶剂中以半柔性链的形式存在.同时,采用SEM和POM(polarized optical microscopy)分别研究了纤维素在溶解前后结构的变化,同样证实在氢氧化锂/尿素体系中纤维素可以很好地被分散,且通过不同的组装方式形成新的集聚态结构.

LiOH/urea aqueous is a attractive solvent system for cellulose. The solution properties of cellulose in the solvent at low concentration were investigated. Three kinds of cellulose with different molecular weights were dissolved in 4. 2 wt% LiOH/12 wt% urea aqueous solution and LiCl/DMAc solvent system, respectively. The dilute solution behavior of cellulose in LiOH/urea aqueous solution was examined by viscometry measurement. The Mark Houwink equation for cellulose in 4. 2 wt% LiOH/12 wt% urea aqueous solution at 25 ℃ over the Mη range from 14. 9 × 10^4 to 32.8 × 10^4 was established as follows： [η]= 1. 695 × 10^-3Mη^0.914 （mL · g^-1）, which implies that the cellulose molecules exist as semi-flexible chains in the aqueous solution. The topographies of both cellulose and regenerated cellulose from its solution were also studied by SEM and POM （polarized optical microscopy） measurements. The results reveal that the cellulose can be well dissolved in the LiOH/urea aqueous solvent system, and self-association should take place during the depositing process.