CNRS Institut Charles Sadron , 23 Rue du Loess, F-67034 Strasbourg, France.
Innventia AB , Drottning Kristinas väg 61, Box 5604, SE-114 86 Stockholm, Sweden.
ACS Nano. 2017 Jan 24;11(1):84-94. doi: 10.1021/acsnano.6b04191. Epub 2016 Dec 6.
We present a simple yet efficient method for orienting cellulose nanofibrils in layer-by-layer assembled films through spray-assisted alignment. While spraying at 90° against a receiving surface produces films with homogeneous in-plane orientation, spraying at smaller angles causes a macroscopic directional surface flow of liquid on the receiving surface and leads to films with substantial in-plane anisotropy when nanoscale objects with anisotropic shapes are used as components. First results with cellulose nanofibrils demonstrate that such fibrils are easily aligned by grazing incidence spraying to yield optically birefringent films over large surface areas. We show that the cellulosic nanofibrils are oriented parallel to the spraying direction and that the orientational order depends for example on the distance of the receiving surface from the spray nozzle. The alignment of the nanofibrils and the in-plane anisotropy of the films were independently confirmed by atomic force microscopy, optical microscopy between crossed polarizers, and the ellipsometric determination of the apparent refractive index of the film as a function of the in-plane rotation of the sample with respect to the plane of incidence of the ellipsometer.
我们提出了一种简单而有效的方法，通过喷雾辅助对准将纤维素纳米纤维在逐层组装的薄膜中定向排列。当以 90°角对着接收表面喷雾时，会产生具有均匀面内取向的薄膜，而当以较小的角度喷雾时，在接收表面上会产生宏观的定向表面液流，并且当使用具有各向异性形状的纳米尺度物体作为组件时，会导致薄膜具有显著的面内各向异性。用纤维素纳米纤维进行的初步结果表明，这些纳米纤维很容易通过掠入射喷雾进行定向排列，从而在大面积上产生光学双折射薄膜。我们表明，纤维素纳米纤维平行于喷雾方向取向，并且取向有序度例如取决于接收表面与喷雾嘴之间的距离。纳米纤维的取向和薄膜的面内各向异性通过原子力显微镜、正交偏振光下的光学显微镜以及椭圆偏振计确定的薄膜表观折射率作为样品相对于椭圆偏振计入射平面的平面内旋转的函数来独立地进行了确认。
