Division of Glycoscience, Department of Chemistry, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, AlbaNova University Centre, Stockholm, SE-106 91, Sweden.
Wallenberg Wood Science Center, Department of Fibre and Polymer Technology, KTH Royal Institute of Technology, Stockholm, SE-100 44, Sweden.
Adv Mater. 2020 Oct;32(42):e2003653. doi: 10.1002/adma.202003653. Epub 2020 Sep 2.
In the native wood cell wall, cellulose microfibrils are highly aligned and organized in the secondary cell wall. A new preparation strategy is developed to achieve individualization of cellulose microfibrils within the wood cell wall structure without introducing mechanical disintegration. The resulting mesoporous wood structure has a high specific surface area of 197 m g when prepared by freeze-drying using liquid nitrogen, and 249 m g by supercritical drying. These values are 5 to 7 times higher than conventional delignified wood (36 m g ) dried by supercritical drying. Such highly mesoporous structure with individualized cellulose microfibrils maintaining their natural alignment and organization can be processed into aerogels with high porosity and high compressive strength. In addition, a strong film with a tensile strength of 449.1 ± 21.8 MPa and a Young's modulus of 51.1 ± 5.2 GPa along the fiber direction is obtained simply by air drying owing to the self-densification of cellulose microfibrils driven by the elastocapillary forces upon water evaporation. The self-densified film also shows high optical transmittance (80%) and high optical haze (70%) with interesting biaxial light scattering behavior owing to the natural alignment of cellulose microfibrils.
在天然木细胞壁中，纤维素微纤维在次生细胞壁中高度排列和组织。开发了一种新的制备策略，以在不引入机械分解的情况下实现纤维素微纤维在木细胞壁结构内的个体化。通过使用液氮冷冻干燥制备的具有高比表面积的介孔木材结构为 197 m g，通过超临界干燥制备的为 249 m g。这些值分别是超临界干燥干燥的常规脱木质素木材（36 m g）的 5 到 7 倍。这种具有高度介孔结构的纤维素微纤维保持其天然排列和组织的个体化，可以加工成具有高孔隙率和高强度压缩的气凝胶。此外，由于纤维素微纤维在水分蒸发时的弹性毛细力的驱动下自致密化，仅通过空气干燥就可以获得具有 449.1 ± 21.8 MPa 拉伸强度和 51.1 ± 5.2 GPa 杨氏模量的沿纤维方向的强膜。自致密化膜还由于纤维素微纤维的天然排列显示出高透光率（80%）和高光学雾度（70%）以及有趣的双轴光散射行为。
