Understanding ion-induced assembly of cellulose nanofibrillar gels through shear-free mixing and in situ scanning-SAXS.
Understanding ion-induced assembly of cellulose nanofibrillar gels through shear-free mixing and in situ scanning-SAXS.
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DOI：
10.1039/d1na00236h
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发表时间：
2021-08-25
影响因子：
4.7
通讯作者：
Hsiao BS
中科院分区：
文献类型：
--
作者：
Rosén T;Wang R;He H;Zhan C;Chodankar S;Hsiao BS
在过去的十年中，纤维素纳米原纤维（CNFs）作为制造生物相容性和可生物降解的新型先进材料的基石显示出巨大的潜力。单个CNF的优异力学性能可以通过在流体动力学校准和装配过程中的仔细控制转移到宏观纤维中。这些过程的优化依赖于对过程中纳米纤维动力学的理解，这反过来又需要原位表征。在这里，我们使用无剪切混合实验结合扫描小角度x射线散射（扫描- saxs）来提供分散的纤维素纳米原纤维（CNFs）在与氯化钠溶液混合后的原位组装过程中的时间分辨纳米尺度动力学。单价离子的加入导致过渡到体积跨越阻滞（凝胶）状态。CNFs的跃迁与粒子的片段聚集有关，导致连接网络和减少布朗运动，从而保持排列结构。此外，我们发现拉伸流动似乎促进了这些片段聚集体的形成，这反过来又为CNFs纺丝的无剪切工艺中获得的优越材料性能提供了可理解的解释。这一观察结果清楚地强调了根据分散的纳米颗粒的形态和相互作用需要不同的组装策略，这项工作可以用作改进纳米材料工艺的指导。利用无剪切混合实验中的原位x射线散射，研究了纤维素纳米原纤维的时间分辨离子诱导凝胶转变。
During the past decade, cellulose nanofibrils (CNFs) have shown tremendous potential as a building block to fabricate new advanced materials that are both biocompatible and biodegradable. The excellent mechanical properties of the individual CNF can be transferred to macroscale fibers through careful control in hydrodynamic alignment and assembly processes. The optimization of such processes relies on the understanding of nanofibril dynamics during the process, which in turn requires in situ characterization. Here, we use a shear-free mixing experiment combined with scanning small-angle X-ray scattering (scanning-SAXS) to provide time-resolved nanoscale kinetics during the in situ assembly of dispersed cellulose nanofibrils (CNFs) upon mixing with a sodium chloride solution. The addition of monovalent ions led to the transition to a volume-spanning arrested (gel) state. The transition of CNFs is associated with segmental aggregation of the particles, leading to a connected network and reduced Brownian motion, whereby an aligned structure can be preserved. Furthermore, we find that the extensional flow seems to enhance the formation of these segmental aggregates, which in turn provides a comprehensible explanation for the superior material properties obtained in shear-free processes used for spinning filaments from CNFs. This observation clearly highlights the need for different assembly strategies depending on morphology and interactions of the dispersed nanoparticles, where this work can be used as a guide for improved nanomaterial processes. Using in situ X-ray scattering in a shear-free mixing experiment, the time-resolved ion-induced gel transition of cellulose nanofibrils is studied.
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