Crystal structures and crystalline elastic modulus of paramylon esters
Crystal structures and crystalline elastic modulus of paramylon esters
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DOI：
10.1016/j.polymer.2019.03.002
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发表时间：
2019-05
期刊：
影响因子：
4.6
通讯作者：
Hongyi Gan;T. Kabe;S. Kimura;T. Hikima;M. Takata;T. Iwata
中科院分区：
文献类型：
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作者：
Hongyi Gan;T. Kabe;S. Kimura;T. Hikima;M. Takata;T. Iwata
副淀粉是裸藻光合作用合成的β-1，3-葡聚糖。本研究合成了4种拟青霉酯衍生物：丙酸拟青霉酯（PaPr）、丁酸拟青霉酯（PaBu）、戊酸拟青霉酯（PaVa）和己酸拟青霉酯（PaHe），并通过广角X射线衍射测定了它们的晶体结构。所有的反射被索引到一个六方晶系和所有的分子链具有五重螺旋对称沿着的分子轴，尽管不同的侧链长度的酯基团。随着酯基侧链长度的增加，晶格常数增大。平行于纤维轴（El）的PaPr、PaBu和PaVa的结晶弹性模量通过在SPring-8（其为大型同步辐射设备）上的时间分辨X射线衍射测定。PaPr、PaBu和PaVa的晶体弹性模量分别为2.5、1.9和1.0 GPa。E1值的减小主要是由于分子链的横截面积增大所致，而横截面积的增大受侧链长度的影响。的纤维素酯的E1值是十分之一，以前报道的纤维素酯。这似乎是因为主链的螺旋结构不同。
Paramylon is aβ-1,3-glucan photosynthesized byEuglena. In this study, the four paramylon ester derivatives, paramylon propionate (PaPr), paramylon butyrate (PaBu), paramylon valerate (PaVa), paramylon hexanoate (PaHe), were prepared and their crystal structures were determined by wide-angle X-ray diffraction. All of the reflections are indexed to a hexagonal crystal system and all of the molecular chains have five-fold screw symmetry along the molecular axes, despite of the different side-chain lengths of the ester groups. The crystal lattice parameters increase with increasing of side-chain length of the ester groups. The crystalline elastic modulus of PaPr, PaBu, and PaVa parallel to the fiber axis (El) were determined by time-resolved X-ray diffraction at SPring-8, which is a large synchrotron radiation facility. The crystalline elastic modulus of PaPr, PaBu, and PaVa are 2.5, 1.9, and 1.0 GPa, respectively. The decreasingElvalues are mainly caused by increasing of cross-sectional area of the molecular chains, which is affected by the side-chain length. TheElvalues of the paramylon esters are one-tenth those of previously reported cellulose esters. This seems to be because of the different helical structure of the backbone chain.