Cellulose and Ionic liquids can form new types of complex crystals growing in form of spherulites. Microfocus X-ray diffraction on selected location of a spherulite, formed from cellulose solution in 1-allyl-3-methylimidazolium chloride (AmimCl) by water vapor diffusion, gave diffraction patterns of fiber-type texture that could be used to index the diffraction spots. The unit cell dimension was tetragonal with a = b = 12.92 Å, c = 10.4 Å, at room temperature and a = b = 12.8 Å and c = 10.45 Å at 100 K with α = β = γ = 90˚. However, the symmetry of the molecule and stoichiometry suggests a space group P2₁2₁2₁, compatible with chiral chain molecule with the systematic absence of odd-order h00, 0k0, and 00l reflections. The spherulite consists of lamellar crystallites rotating along the b axis, the latter lying in the radial direction. The half pitch of the order of 12 µm according to polarized microscopy, was smaller than the beam size leading to a fiber-like pattern. The crystallite sizes estimated from the diffraction broadening were at least of the order of 150 nm along a and b direction, limited by the instrument resolution, and about 15 ~ 30 nm along c direction. The 10.4 Å of c-axis is the typical length of two-fold helix of cellulose suggesting that cellulose chain is parallel to the c-axis. The unit cell would contain 4 glucose residues, 4 ionic liquid molecules and 4–8 water molecules.

Graphic abstract

中文翻译：

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纤维素/离子液体球晶中的扭曲拟四方正交晶层状晶体

纤维素和离子液体可以形成以球晶形式生长的新型复杂晶体。由水蒸气在1-烯丙基-3-甲基咪唑鎓盐（AmimCl）中的纤维素溶液中的纤维素溶液形成的球晶的选定位置上的微焦点X射线衍射产生了可用于索引衍射点的纤维型织构的衍射图。 在室温下，晶胞尺寸为四边形，a  =  b  = 12.92Å，c = 10.4Å， 在100 K下，a  =  b  = 12.8Å和c = 10.45Å，α  =  β  =  γ  = 90。但是，分子的对称性和化学计量表明存在一个空间群P 2 ₁ 2 ₁ 2 _{1 1}，与手性链分子兼容，但系统性地不存在奇数h00、0k0和00l反射。球晶由沿b轴旋转的层状微晶组成，后者沿径向。根据偏振显微镜，半节距约为12μm，小于导致纤维状图案的光束尺寸。由衍射展宽估计的微晶尺寸沿a和b方向至少约为150nm ，受仪器分辨率的限制，沿c方向约为15〜30nm 。c的10.4Å轴是纤维素的两倍螺旋线的典型长度，表明纤维素链平行于c轴。晶胞将包含4个葡萄糖残基，4个离子液体分子和4-8个水分子。

图形摘要