Magnetic alignment of the chiral nematic phase of a cellulose microfibril suspension
Magnetic alignment of the chiral nematic phase of a cellulose microfibril suspension
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DOI：
10.1021/la0475728
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发表时间：
2005-03-01
期刊：
影响因子：
3.9
通讯作者：
Horii, F
中科院分区：
文献类型：
--
作者：
Kimura, F;Kimura, T;Horii, F
通过酸水解被囊素的纤维素外套膜制备了稳定的被囊纤维素微纤丝悬浮液。它们在超过临界浓度时形成了手性双相。外磁场以两种不同的方式施加到手性双相，以控制其相结构。(i)使用范围为1-28 T的静磁场在磁场方向上对齐手性螺旋轴（螺旋轴）。(ii)施加旋转磁场（5 T，10 rpm）以解绕螺旋并形成双相。这些现象被解释在各向异性的纤维素微纤维的抗磁化率。微纤维的抗磁性磁化率在平行于纤维轴的方向（chi（垂直于））上比在垂直于纤维轴的方向（chi-垂直于）上小，即chi（II）< chi（垂直于）< 0。因为螺旋轴与纤维轴的法线方向一致，所以螺旋轴平行于所施加的场对准。另一方面，旋转磁场诱导最小磁化率轴的单轴排列，即在本例中的chi（II），并引起螺旋的解旋。
Stable suspensions of tunicate cellulose microfibrils were prepared by acid hydrolysis of the cellulosic mantles of tunicin. They formed a chiral nematic phase above a critical concentration. External magnetic fields were applied to the chiral nematic phase in two different manners to control its phase structure. (i) Static magnetic fields ranging 1-28 T were used to align the chiral nematic axis (helical axis) in the field direction. (ii) A rotating magnetic field (5 T, 10 rpm) was applied to unwind the helices and to form a nematic phase. These phenomena were interpreted in terms of the anisotropic diamagnetic susceptibility of the cellulose microfibril. The diamagnetic susceptibility of the microfibril is smaller in the direction parallel (chi(perpendicular to)) to the fiber axis than in the direction perpendicular (chi-perpendicular to) to the fiber axis, that is,chi(II) < chi(perpendicular to) < 0. Because the helical axis coincides with the direction normal (perpendicular to) to the fiber axis, the helical axis aligned parallel to the applied field. On the other hand, the rotating magnetic field induced the uniaxial alignment of the smallest susceptibility axis, that is, chi(II) in the present case, and brought about unwinding of the helices.