Carlsson Daniel O, Lindh Jonas, Strømme Maria, Mihranyan Albert
Nanotechnology and Functional Materials, Department of Engineering Sciences, Uppsala University, Box 534, 751 21 Uppsala, Sweden.
Biomacromolecules. 2015 May 11;16(5):1643-9. doi: 10.1021/acs.biomac.5b00274. Epub 2015 Apr 9.
The susceptibility of Iα- and Iβ-dominated cellulose to TEMPO-mediated oxidation was studied in this work since the cellulose Iα-allomorph is generally considered to be thermodynamically less stable and therefore more reactive than the cellulose Iβ-allomorph. Highly crystalline Cladophora nanocellulose, which is dominated by the Iα-allomorph, was oxidized to various degrees with TEMPO oxidant via bulk electrolysis in the absence of co-oxidants. Further, the Cladophora nanocellulose was thermally annealed in glycerol to produce its Iβ-dominated form and then oxidized. The produced materials were subsequently studied using FTIR, CP/MAS (13)C NMR, XRD, and SEM. The solid-state analyses confirmed that the annealed Cladophora cellulose was successfully transformed from an Iα- to an Iβ-dominated form. The results of the analyses of pristine and annealed TEMPO-oxidized samples suggest that Iα- and Iβ-dominated cellulose do not differ in susceptibility to TEMPO-oxidation. This work hence suggests that cellulose from different sources are not expected to differ in susceptibility to the oxidation due to differences in allomorph composition.
由于纤维素Iα同素异形体通常被认为在热力学上稳定性较差，因此比纤维素Iβ同素异形体更具反应活性，本研究考察了Iα和Iβ为主的纤维素对TEMPO介导氧化的敏感性。以Iα同素异形体为主的高度结晶的枝管藻纳米纤维素，在无共氧化剂的情况下通过本体电解，用TEMPO氧化剂进行不同程度的氧化。此外，将枝管藻纳米纤维素在甘油中进行热退火，以产生其以Iβ为主的形式，然后进行氧化。随后使用傅里叶变换红外光谱（FTIR）、交叉极化/魔角旋转（13）C核磁共振（CP/MAS (13)C NMR）、X射线衍射（XRD）和扫描电子显微镜（SEM）对所制备的材料进行研究。固态分析证实，退火后的枝管藻纤维素成功地从以Iα为主的形式转变为以Iβ为主的形式。对原始和退火后的TEMPO氧化样品的分析结果表明，以Iα和Iβ为主的纤维素对TEMPO氧化的敏感性没有差异。因此，这项工作表明，由于同素异形体组成的差异，不同来源的纤维素对氧化的敏感性预计不会有所不同。
