A NIR Study on Hydrogen Bonds of Bamboo-Based Cellulose Ⅱ
DONG Pei-jie1, ZHANG Wen-bo1*, LU Wei2
1. College of Material Science and Technology, Beijing Forestry University, Beijing 100083, China
2. China Information Center of Light Industry, Beijing 100833, China
Abstract：Cellulose is a renewable natural hydrophilic polymer, and its huge hydrogen bond grid forms a variety of different crystal structures. There are five crystalline variants of cellulose (cellulose Ⅰ, Ⅱ, Ⅲ, Ⅳ and Ⅹ), of which cellulose Ⅱ is formed from cellulose Ⅰ (natural cellulose) after regeneration or mercerization, is the lowest surface free energy and the most stable performance among the five crystal varieties, mainly due to the antiparallel chain structure of cellulose Ⅱ, which is opposite to the parallel chain structure of cellulose I, and has additional intermolecular hydrogen bonds compared with cellulose I. Therefore, in view of the sensitivity of near-infrared spectroscopy (NIRS) to the hydrogen-containing group, and the crystalline structure of cellulose contains a large number of hydrogen bonds, this makes it possible for NIRS to analyze the degree of hydrogen bond destruction of cellulose by hydrogen containing functional groups, and to detect and quantitatively evaluate the crystalline structure of cellulose qualitatively. So far, there are very few studies on the hydrogen bonding of cellulose crystal variants, and the hydrogen bonding of bamboo cellulose Ⅱ and its derivatives has not been reported at home and abroad. In the study, cellulose Ⅰ was prepared from bamboo, and bamboo-based cellulose Ⅱ was obtained through mercerization, which NIRS investigated hydrogen bonds, the results were compared with bamboo powder and bamboo-based cellulose Ⅰ. Besides, the crystallinity of bamboo powder and bamboo-based cellulose was quantitatively evaluated by NIRS. The results can be drawn as follows: (1) the differences of NIRS among bamboo powder, bamboo-based cellulose Ⅰ and Ⅱ varied little, hydrogen bonding were quantitatively remarkable, but were qualitatively slight in the amorphous region; (2) compared with bamboo powder, the crystal structure of bamboo-based cellulose I remained unchanged, while bamboo-based cellulose Ⅱ occurred two absorbance peaks in the semi-crystalline region; (3) in the crystalline region a strong hydrogen bonding absorbance peak reflected the first overtone of hydroxyl group stretching vibration was observed at the wavenumber of 6 292 cm-1 assigned to the intermolecular bond of O2—H2···O6 of cellulose Ⅰ, which shifted to 6 354 cm-1 for bamboo-based cellulose Ⅱ. We deduced the absorbance peak in cellulose Ⅱ was assigned to the intermolecular bond of O2—H2···O2 due to anti-parallel structure of cellulose confirmation; (4) a good correlation among crystallinity was obtained by NIRS with the results of XRD analysis. The above research shows that the hydrogen bonding in the crystalline region of cellulose shifts in the near-infrared characteristic band and forms double peaks in the semi-crystalline region, which were the main characteristics of bamboo-based cellulose Ⅱ different from bamboo-based cellulose Ⅰ. Simultaneously, it is feasible to use NIRS to study the hydrogen bonding of various celluloses and predict their crystallinity.
董沛杰，张文博，陆 薇. 竹基纤维素Ⅱ氢键结合的近红外光谱研究[J]. 光谱学与光谱分析, 2021, 41(04): 1260-1264.
DONG Pei-jie, ZHANG Wen-bo, LU Wei. A NIR Study on Hydrogen Bonds of Bamboo-Based Cellulose Ⅱ. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2021, 41(04): 1260-1264.
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