Dynamic analysis of crystal transformation of cellulose

(1)在氦气气氛中加热一层高度定向的枝叶状纤维素膜，使纤维素Ia转变为纤维素Ib。在这一过程之后，位置灵敏正比计数器(PSPC)成功地记录了晶格的变化。虽然纤维素Ia向Ib转化的确切分子机制尚未阐明，但我们的结果将为确定其是否涉及分子链的旋转提供重要线索。(2)PSPC的使用使我们能够同时测定苎麻纤维晶格在横向和纵向的变形。用纤维张力仪对100根麻纤维进行了拉伸试验，用PSPC记录了三次赤道反射，得到了一张负荷伸长图。对同样获得的经向反射负荷伸长数据进行了分析，得到了纤维素晶体的纵向弹性模量和泊松比分别为129 Gpa和0.34。(3)用PSPC和成像板(IP)研究了氢氧化钠对苎麻纤维的溶胀，得到了新的信息。当在400根雷米纤维束中加入50微升等分的氢氧化钠时，可以同时跟踪三个主要赤道反射的变化。比较积分强度的变化，得出晶格的变化不是各向同性的，但a轴方向的变化先于其他方向的变化，即ab平面上的氢键分子片似乎从微晶上剥离。(4)纤维素-硫氰酸钙络合物在水中再生形成纤维素I。该络合物是一种定义明确的纤维晶体，与碱性纤维素有明显的不同。

(1) A highly oriented film of microcrystalline Cladophora cellulose was heated in helium atmosphere, resulting in the transformation of cellulose Ia to cellulose Ib. This process was followed by a position-sensitive proportional counter (PSPC) and the change in the crystal lattice was successfully recorded. While the exact molecular mechanism of the transformation from cellulose Ia to Ib is not elucidated, our present results will give an important clue to determine whether it involves the rotation of molecular chain.(2) The use of PSPC allowed us to determine simultaneously the deformation of crystal lattice of ramie fiber in both lateral and longitudinal directions. A bundle of 100 ramie fibers was subjected to tensile stress by using the fiber-tensioning device, and a load elongation chart was obtained by recording the three major equatorial reflections with PSPC.Analysis of similarly obtained load-elongation data for the meridional reflection gave longitudinal elastic modulus and poisson ratio of cellulose crystal, 129Gpa and 0.34, respectively.(3) Swelling of ramie fiber by aq.Sodium hydroxice was studied by the use of PSPC and imaging plate (IP), resulting in new information. When aq.NaOH was added in 50 uL aliquots of to a bundle of 400 remie fibers, the change in three major equatorial reflections could be followed simultaneously. Comparison of the change in integral intensity led to the conclusion that the change in crystal lattice does not proceed isotropically but the change in a-axis direction precedes those in other directions, i.e., the hydrogen-bonded molecular sheet in the ab plane appears to be peeled off from the crystallite.(4) cellulose-calcium thiocyanate complex was found to form cellulose I by regenerating in water. This complex was found to be a well-defined fibrous crystal, which is remarkably different from that of alkali cellulose.