Microstructural, Thermal, Crystallization, and Water Absorption Properties of Films Prepared from Never‐Dried and Freeze‐Dried Cellulose Nanocrystals,Macromolecular Materials and Engineering

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Microstructural, Thermal, Crystallization, and Water Absorption Properties of Films Prepared from Never‐Dried and Freeze‐Dried Cellulose Nanocrystals
Macromolecular Materials and Engineering ( IF 4.2 ) Pub Date : 2020-11-23 , DOI: 10.1002/mame.202000462
Kazi M. Zakir Hossain ₁ , Vincenzo Calabrese ₁ , Marcelo A. da Silva ₁ , Julien Schmitt ₁ , Saffron J. Bryant ₁ , Md Towhidul Islam ₂ , Reda M. Felfel _{3,

4} , Janet L. Scott _{1,

5} , Karen J. Edler _{1,

5}

Affiliation

In this paper, the microstructural, optical, thermal, crystallization, and water absorption properties of films prepared from never-dried (ND) and freezedried (FD) cellulose nanocrystals (CNCs) are reported. Morphology of the ND CNCs reveals a needle-like structure, while after freeze-drying, they show a flake-like morphology. Microstructural analysis of ND and FD CNCs are further studied via small angle X-ray scattering to probe interactions. ND CNCs yield a transparent film with a low surface roughness (14 ± 4 nm), while the FD CNC film evidence a significant reduction of their transparency due to their higher surface roughness (134 ± 20 nm). Although Fourier transform infrared spectroscopy and energy-dispersive X-ray spectroscopy analyses reveal no chemical change occurs during the freeze-drying process, yet a more intense thermal degradation profile is observed for FD CNC film, probably due to the higher oxygen ingress within the gaps created between the stacked flakes. This, in turn, results in a greater loss of crystallinity at a higher temperature (300 °C) compared to the ND CNC film. A rapid decrease in water contact angle of the FD CNC film proves that the morphology of flakes and their orientation within the film has a strong influence in increasing water absorption capacity.

中文翻译：

从未干燥和冷冻干燥的纤维素纳米晶体制备的薄膜的微观结构、热、结晶和吸水性能

本文报道了从未干燥 (ND) 和冷冻干燥 (FD) 纤维素纳米晶体 (CNC) 制备的薄膜的微观结构、光学、热、结晶和吸水性能。ND CNCs 的形态显示针状结构，而在冷冻干燥后，它们显示出片状形态。通过小角度 X 射线散射探测相互作用，进一步研究了 ND 和 FD CNC 的微观结构分析。ND CNC 产生具有低表面粗糙度 (14 ± 4 nm) 的透明薄膜，而 FD CNC 薄膜由于其较高的表面粗糙度 (134 ± 20 nm)，证明其透明度显着降低。尽管傅里叶变换红外光谱和能量色散 X 射线光谱分析表明在冷冻干燥过程中没有发生化学变化，然而，对于 FD CNC 薄膜，观察到更强烈的热降解曲线，这可能是由于在堆叠薄片之间产生的间隙内进入的氧气较多。与 ND CNC 薄膜相比，这反过来又导致在更高温度 (300 °C) 下更大的结晶度损失。FD CNC 薄膜的水接触角迅速减小，证明薄片的形态及其在薄膜内的取向对增加吸水能力有很大影响。

更新日期：2020-11-23

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