An innovative method combining frontal filtration with ultraviolet (UV) curing has been implemented to design cellulosic nanocomposite films with controlled anisotropic textures from nanometric to micrometric length scales. Namely, an aqueous suspension containing poly (ethylene glycol) diacrylate polymer (PEGDA) as a photocurable polymer and cellulose nanocrystals (CNCs) at a 70/30 mass ratio was processed by frontal filtration, followed by - UV-curing in a dedicated cell. This procedure allowed designing nanocomposite films with highly oriented and densely-packed CNCs, homogeneously distributed in a PEGDA matrix over a thickness of 500 μm. The nanocomposite films were investigated with small-angle X-ray scattering (SAXS), by raster-scanning along their height with a 25 μm vertically-collimated X-ray beam. The CNCs exhibited a high degree of orientation, with their director aligned parallel to the membrane surface, combined with an increase in the degree of alignment as concentration increased towards the membrane surface. Scanning electron microscopy images of fractured films showed the presence of regularly spaced bands lying perpendicular to the applied transmembrane pressure, highlighting the presence of a chiral nematic (cholesteric) organization of the CNCs with a pitch gradient that increased from the membrane surface to the bulk.

中文翻译：

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通过过滤和紫外线固化纤维素纳米晶体悬浮液制备的具有螺距梯度的手性向列纳米复合材料

一种将正面过滤与紫外线（UV）固化相结合的创新方法已被实施，以设计具有从纳米到微米长度尺度的受控各向异性纹理的纤维素纳米复合材料薄膜。即，通过正面过滤处理含有质量比为70/30的聚乙二醇二丙烯酸酯聚合物(PEGDA)和纤维素纳米晶体(CNC)的水悬浮液，然后在专用单元中进行UV固化。该程序允许设计具有高度定向和密集堆积的 CNC 的纳米复合材料薄膜，这些 CNC 均匀分布在厚度为 500 μm 的 PEGDA 矩阵中。通过使用 25 μm 垂直准直 X 射线束沿其高度进行光栅扫描，利用小角 X 射线散射 (SAXS) 对纳米复合材料薄膜进行了研究。 CNC 表现出高度的取向，其导向器平行于膜表面排列，并且随着朝向膜表面的浓度增加，排列程度也随之增加。断裂薄膜的扫描电子显微镜图像显示，存在垂直于施加的跨膜压力的规则间隔的带，突出显示了 CNC 的手性向列（胆甾型）组织的存在，其节距梯度从膜表面到本体增加。