纤维素拉曼光谱的单体仿真方法研究

doi:10.3964/j.issn.1000-0593(2024)01-0164-05

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Abstract Cellulose is a macromolecular polysaccharide composed of glucose, the most abundant, cheapest and easiest to obtain natural polymer in the world. Cellulose, as the oldest and most abundant natural polymer, has attracted much attention in research. The controllability of cellulose depends on its molecular weight, size and structure, and Raman spectroscopy has “fingerprint characteristics”, which can identify different cellulose fibers, as well as historical aging textile fiber materials. However, it is difficult to simulate cellulose as a macromolecular polysaccharide theoretically. In this study, we propose using the basic unit to simulate macromolecular spectrum, and use cellulose monomer to simulate Raman spectrum to analyze the spectral properties of cellulose macromolecules. In this paper, based on density functional theory, the Raman spectra of cellulose monomers and cellulose double links under different external electric fields (a. u.) were calculated under the basis set conditions of B3LYP/6-31g (d, p) using Gaussian 16 software. The study shows that the Raman spectrum of cellulose monomer has characteristic peaks at 449, 597, 842, 1 127, 1 361, 1 395 and 3 005 cm^-1 without the action of the external electric field. The vibration analysis shows that these Raman peaks are respectively composed of the ring (C6—C4—O20) stretching vibration, C—C—H twisting vibration, ring (C4—O20—C2) stretching vibration, glycosidic bond (C2—O1—C8) stretching vibration, CH₂ bending vibration The expansion vibration of CH₂ is generated. Compared with the experimental value, the simulated Raman spectrum of cellulose monomer is consistent with the measured Raman spectrum of natural cellulose, so the first principle calculation of cellulose monomer can reflect the Raman spectrum characteristics of cellulose macromolecules. When the external electric field changes from the negative direction to the positive direction and gradually increases, the amplitude of the C—C—H torsional vibration of the ring corresponding to 597 cm^-1 has no obvious change. With no electric field as the benchmark, when the external electric field is applied, the vibration energy reduces the spectral red shift; The stretching vibration amplitude of the glycoside bond (C2—O1—C8) corresponding to 1 127 cm^-1 decreased significantly, and the spectrum showed a blue shift; The characteristic peak spectrum of the bending vibration of CH₂ at 1 395 cm^-1 shows a blue shift, and the spectrum generated at 1 361 cm^-1 shows a blue shift first, then a red shift, and then a blue shift again. It is speculated that the bending vibration area is more susceptible to the influence of the skeleton vibration and environmental changes. Comparing the difference between the Raman spectra of cellulose monomer and double chain link, in addition to the obvious characteristic peaks of the monomer, the double chain link molecule has obvious characteristic peaks at 1 041 and 151 cm^-1, which are respectively produced by C—O stretching vibration of secondary alcohol and C—O—H bending vibration, which can supplement the Raman spectra of cellulose monomer. These conclusions provide a theoretical basis for studying the spectra of cellulose under the action of external electric field and a new method for studying and analyzing the Raman spectra of other macromolecular polymers.

Key words：Cellulose; The electric field; Raman spectroscopy

Received: 2022-04-19 Accepted: 2022-12-17

ZTFLH:

O657.37

Corresponding Authors: WANG Fang-yuan E-mail: wangfy@guet.edu.cn

Cite this article:

WANG Xin-qiang,CHU Pei-zhu,XIONG Wei, et al. Study on Monomer Simulation of Cellulose Raman Spectrum[J]. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2024, 44(01): 164-168.

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2024)01-0164-05 OR https://www.gpxygpfx.com/EN/Y2024/V44/I01/164