Chen Xuming, Burger Christian, Wan Fen, Zhang Jun, Rong Lixia, Hsiao Benjamin S, Chu Benjamin, Cai Jie, Zhang Lina
Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, USA.
Biomacromolecules. 2007 Jun;8(6):1918-26. doi: 10.1021/bm061186i. Epub 2007 May 2.
In this study, structure changes of regenerated cellulose fibers wet-spun from a cotton linter pulp (degree of polymerization approximately 620) solution in an NaOH/urea solvent under different conditions were investigated by simultaneous synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS). WAXD results indicated that the increase in flow rate during spinning produced a better crystal orientation and a higher degree of crystallinity, whereas a 2-fold increase in draw ratio only affected the crystal orientation. When coagulated in a H2SO4/Na2SO4 aqueous solution at 15 degrees C, the regenerated fibers exhibited the highest crystallinity and a crystal orientation comparable to that of commercial rayon fibers by the viscose method. SAXS patterns exhibited a pair of meridional maxima in all regenerated cellulose fibers, indicating the existence of a lamellar structure. A fibrillar superstructure was observed only at higher flow rates (>20 m/min). The conformation of cellulose molecules in NaOH/urea aqueous solution was also investigated by static and dynamic light scattering. It was found that cellulose chains formed aggregates with a radius of gyration, Rg, of about 232 nm and an apparent hydrodynamic radius, Rh, of about 172 nm. The NaOH/urea solvent system is low-cost and environmentally friendly, which may offer an alternative route to replace more hazardous existing methods for the production of regenerated cellulose fibers.
在本研究中，通过同步辐射广角X射线衍射（WAXD）和小角X射线散射（SAXS），研究了在不同条件下由棉短绒浆粕（聚合度约为620）溶液在NaOH/尿素溶剂中湿法纺丝得到的再生纤维素纤维的结构变化。WAXD结果表明，纺丝过程中流速的增加产生了更好的晶体取向和更高的结晶度，而拉伸比增加两倍仅影响晶体取向。当在15℃的H2SO4/Na2SO4水溶液中凝固时，再生纤维表现出最高的结晶度，并且晶体取向与通过粘胶法制备的商业粘胶纤维相当。SAXS图谱在所有再生纤维素纤维中均呈现出一对子午向最大值，表明存在层状结构。仅在较高流速（>20 m/min）下观察到纤维状超结构。还通过静态和动态光散射研究了NaOH/尿素水溶液中纤维素分子的构象。发现纤维素链形成了回转半径Rg约为232 nm、表观流体力学半径Rh约为172 nm的聚集体。NaOH/尿素溶剂体系成本低且环境友好，这可能为替代更具危害性的现有再生纤维素纤维生产方法提供一条途径。
