Structural changes in α-chitin through nanofibrillation by high-pressure homogenization in water

Autor: Kota Ogura, Yuto Kaku, Yuko Ono, Akira Isogai, Shuji Fujisawa
Rok vydání: 2020
Předmět:
Zdroj: Polymer Journal. 52:813-818
ISSN: 1349-0540
0032-3896
DOI: 10.1038/s41428-020-0322-0
Popis: Chitin nanofiber was prepared from purified crab shell chitin by repeated high-pressure homogenization in water. The chitin nanofiber/water dispersion thus prepared was viscous and translucent, and maintained a stable dispersion at room temperature for several months. AFM images showed that the chitin nanofibers had heterogeneous network structures with widths ranging from several nanometers to several tens of nanometers. Some kinks and twisted structures were also observed in the AFM images. X-ray diffraction patterns showed that both the crystallinity index and crystal width of the original alpha-chitin decreased with nanofibrillation. Solid-state 13C-NMR spectra showed that the chemical shifts of all carbons were unchanged before and after nanofibrillation, and that all C6–OH groups had the gauche-gauche conformation irrespective of the crystalline fibril surfaces and insides. The degree of N-acetylation increased from 0.83 to 0.98, which was probably due to C2–NH2 groups present in the original chitin being partially removed during high-pressure homogenization in water. The original chitin and chitin nanofiber were dissolved in 8% LiCl/DMAc, and the solutions after dilution to 1% LiCl/DMAc were subjected to size-exclusion chromatography combined with multi-angle laser-light scattering to determine their molar masses and molar mass distributions. The weight-average molar mass (Mw) value of the original chitin was 271,200 (degree of polymerization [DP] ~1340). The Mw value of the chitin nanofiber was 165,500 (DP 820), showing that the DP of the original chitin decreased by 40% through the nanofibrillation in water to form the chitin nanofiber. Chitin nanofibers were prepared from purified crab-shell chitin particles by repeated high-pressure homogenization in water. AFM images showed that the chitin nanofibers had heterogeneous network structures. X-ray diffraction patterns showed that both the crystallinity index and crystal width of the original α-chitin decreased by nanofibrillation. Solid-state 13C-NMR spectra showed that all C6–OH groups had the gauche–gauche conformation. The degree of N-acetylation increased from 0.83 to 0.98 by nanofibrillation, while the weight-average molar masses of the original chitin and chitin nanofibers were 271,200 and 165,500, respectively.
Databáze: OpenAIRE
Externí odkaz: