Chiral Nematic Structure of Cellulose Nanocrystal Suspensions and Films; Polarized Light and Atomic Force Microscopy.
Chiral Nematic Structure of Cellulose Nanocrystal Suspensions and Films; Polarized Light and Atomic Force Microscopy.
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DOI：
10.3390/ma8115427
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发表时间：
2015-11-18
期刊：
影响因子：
--
通讯作者：
Mu X
中科院分区：
文献类型：
--
作者：
Gray DG;Mu X
纤维素类液晶溶液和悬浮液形成手性液晶相，其在液晶状态下显示出丰富多样的光学织构。这些有序结构可以通过蒸发溶剂或悬浮介质而保持在固体膜中。采用偏光显微镜、光学轮廓仪和原子力显微镜研究了纤维素纳米晶（CNC）水悬浮液的成膜过程。尝试定性地解释所观察到的纹理在悬浮液和薄膜中的纤维素纳米晶体的取向，以及由蒸发过程引起的取向的变化。蒸发液滴内的传质导致形成凸起的环，其大小取决于后退接触线的钉扎程度。在短的长度尺度的干膜的AFM显示的CNC在膜的自由表面处的径向取向，沿着与径向高度变化的周期约为P/2，归因于各向异性收缩的手性结构。
Cellulosic liquid crystalline solutions and suspensions form chiral nematic phases that show a rich variety of optical textures in the liquid crystalline state. These ordered structures may be preserved in solid films prepared by evaporation of solvent or suspending medium. Film formation from aqueous suspensions of cellulose nanocrystals (CNC) was investigated by polarized light microscopy, optical profilometry and atomic force microscopy (AFM). An attempt is made to interpret qualitatively the observed textures in terms of the orientation of the cellulose nanocrystals in the suspensions and films, and the changes in orientation caused by the evaporative process. Mass transfer within the evaporating droplet resulted in the formation of raised rings whose magnitude depended on the degree of pinning of the receding contact line. AFM of dry films at short length scales showed a radial orientation of the CNC at the free surface of the film, along with a radial height variation with a period of approximately P/2, ascribed to the anisotropic shrinkage of the chiral nematic structure.