不同大小统一的纤维素纳米晶体通过多级分离引起的独特的手性向列自组装行为,Langmuir

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不同大小统一的纤维素纳米晶体通过多级分离引起的独特的手性向列自组装行为
Langmuir ( IF 3.7 ) Pub Date : 2016-09-14 00:00:00 , DOI: 10.1021/acs.langmuir.6b02861
Yang Hu ₁ , Noureddine Abidi ₁

Affiliation

纤维素纳米晶体（CNC）是完美的棒状纳米纤维，可以自组装并形成手性向列相。我们发现，不同的尺寸统一的CNC可以形成不同的自组装形态。这项研究报告了一种简便而又新的方法，将宽粒度分布（9-1700 nm）中的原始（未分离的）CNC分为一系列较窄的尺寸范围，以通过精心设计的多级分离工艺获得尺寸统一的CNC，该方法包括具有不同孔径截留值的分层滤膜，然后进行快速加压过滤。与较大尺寸统一的CNC相比，较小尺寸统一的CNC易于自组装成具有较大螺距值的抛光手性向列相。通过数学评估解决了不同手性向列相和螺距值随尺寸变化的区别，这表明各向异性相体积分数的降低与离子强度的增加和刚性棒状结晶性的降低有关CNC是一个关键因素。此外，傅立叶变换红外光谱，热重分析和X射线衍射结果表明，即使尺寸不同的CNC的化学结构和晶体结构保持不变，它们也表现出特定的热稳定性和结晶度。

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Distinct Chiral Nematic Self-Assembling Behavior Caused by Different Size-Unified Cellulose Nanocrystals via a Multistage Separation

Cellulose nanocrystals (CNCs) are perfect rodlike nanofibers that can self-assemble and form a chiral nematic phase. We found that different self-assembling morphologies could be formed by different size-unified CNCs. This study reported a facile and new approach of fractionating raw (unseparated) CNCs in a wide particle size distribution (9–1700 nm) into a series of narrower size ranges to obtain size-unified CNCs via a well-designed multistage separation process composed of layered filter membranes with different pore size cutoffs followed by a fast pressurized filtration. The smaller size-unified CNCs readily self-assembled into polish chiral nematic phases with larger pitch value as compared to larger size-unified CNCs. Such a distinction among different chiral nematic phases and pitch values as functions of size was addressed by a mathematical evaluation, which suggested that the reduced volume fraction of the anisotropic phase as a function of both increased ionic strength and reduced crystallinity of rigid-rod-like CNCs is a critical factor. In addition, Fourier-transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction results revealed that different size-unified CNCs exhibited particular thermal stabilities and crystallinities even though their chemical and crystalline structures remained unchanged. The discrepancies in physicochemical characteristics and self-assembling chiral nematic behavior among different size-unified CNCs may benefit the specific functionalization of cellulose materials using size-unified fibers instead of raw CNCs containing mixed small and large fibers.

更新日期：2016-09-14

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