Abstract

Dissolution and regeneration of cellulose is of vital importance for its end use. In the present work, the effect of different regeneration solvents (i.e. water, ethanol, and N, N-dimethylacetamide (DMAc)) on the characteristics of the regenerated cellulose from lithium bromide trihydrate (LBTH) molten salt was comprehensively investigated. It was found that the regenerated celluloses displayed obvious changes in macro- and micro-morphologies compared with the original microcrystalline cellulose (MCC). Furthermore, after the dissolution and regeneration process, the crystalline structure of cellulose was changed from cellulose I to cellulose II or amorphous structure, and the crystallinity of cellulose clearly decreased due to the deconstruction and rearrangement of cellulose chains. Moreover, the regenerated cellulose with ethanol had a relatively higher degree of crystallinity (70.2%) than that with water (42.3%) and DMAc (33.2%). Both X-ray Diffraction (XRD) and Attenuated Total Reflection Flourier transformed Infrared Spectroscopy (ATR-FTIR) analysis results indicated that ethanol as a regeneration solvent could be more beneficial to rearrange cellulose molecular chains and rebuild a more ordered structure compared to water and DMAc. In addition, thermogravimetric analysis showed that regenerated cellulose from LBTH exhibited a lower decomposition onset temperature and a higher char yield (over 17.8%) compared with the raw MCC (2.8%). The obtained results verified that regeneration solvents could substantially affect the reconstitution of cellulose molecule chains during regeneration as well as the multiscale structures and properties of the regenerated cellulose.

Graphic abstract

中文翻译：

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再生溶剂对三水合溴化锂熔融盐再生纤维素特性的影响

摘要

纤维素的溶解和再生对其最终用途至关重要。在本工作中，全面研究了不同的再生溶剂（即水，乙醇和N，N-二甲基乙酰胺（DMAc））对由溴化锂三水合物（LBTH）熔盐再生的纤维素的特性的影响。发现与原始的微晶纤维素（MCC）相比，再生的纤维素在宏观和微观形态上显示出明显的变化。此外，在溶解和再生过程之后，纤维素的晶体结构从纤维素I改变为纤维素II或无定形结构，并且由于纤维素链的解构和重排，纤维素的结晶度明显降低。此外，与乙醇（42.3％）和DMAc（33.2％）相比，含乙醇的再生纤维素具有较高的结晶度（70.2％）。X射线衍射（XRD）和衰减全反射Flourier转换红外光谱（ATR-FTIR）分析结果均表明，与水和DMAc相比，乙醇作为再生溶剂可能更有利于重新排列纤维素分子链并重建更有序的结构。此外，热重分析表明，与原始MCC（2.8％）相比，LBTH再生的纤维素表现出较低的分解起始温度和较高的炭收率（超过17.8％）。

图形摘要