Cellulose was treated with supercritical water at 668 K and 25 MPa for 0.04 s in this study. The cellulose/water system was transparent at room temperature for a while after supercritical water treatment before a precipitate gradually appeared over several hours. The precipitation process was monitored by synchrotron X-ray scattering. The scattering functions of fractal systems and flat-like structures were utilized to explain the experimentally observed small-angle scattering profiles. Immediately after supercritical water treatment, the cellulose appeared to dissolve with a fractal dimension D of approximately 1, indicating that the cellulose molecules were rigid, followed by aggregation into a 5-nm-thick flat-like structure. The flat-like structure was determined to be similar to the molecular sheets observed during the early stages of precipitation in the cellulose/aqueous sodium hydroxide and cellulose/aqueous lithium hydroxide/urea systems. Resultant regenerated cellulose had high crystallinity, large crystal size, and a low degree of polymerization.

在本研究中，纤维素用 668 K 和 25 MPa 的超临界水处理 0.04 秒。在超临界水处理后，纤维素/水体系在室温下透明一段时间，然后在几个小时内逐渐出现沉淀。通过同步加速器 X 射线散射监测沉淀过程。利用分形系统和平面结构的散射函数来解释实验观察到的小角散射剖面。超临界水处理后，纤维素立即溶解，分形维数 D 约为 1，表明纤维素分子是刚性的，随后聚集成 5 nm 厚的扁平状结构。扁平状结构被确定为类似于在纤维素/氢氧化钠水溶液和纤维素/氢氧化锂水溶液/尿素体系中沉淀的早期阶段观察到的分子片。所得再生纤维素结晶度高、晶体尺寸大、聚合度低。