期刊
CARBOHYDRATE POLYMERS
卷 143, 期 -, 页码 327-335出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.carbpol.2016.01.048
关键词
Cellulose nanocrystals; CNC; Mercerization; Polymorphs; Cellulose I and II; Crystallinity; Crystallite size
资金
- Special Fund for Forestry Scientific Research in the Public Interest [201404510]
- National Natural Science Foundation of China [31200454, 31270613]
- Qing-Lan Project, Jiangsu Co-Innovation Center for Efficient Processing and Utilization of Forest Resource (NJFU)
- Priority Academic Program Development of Jiangsu Higher Education Institutions
- China Scholarship Council
- Academy of Finland Centres of Excellence Programme Molecular Engineering of Biosynthetic Hybrid Materials Research (HYBER)
Polymorphic and morphological transformations of cellulosic materials are strongly associated to their properties and applications, especially in the case of emerging nanocelluloses. Related changes that take place upon treatment of cellulose nanocrystals (CNC) in alkaline conditions are studied here by XRD, TEM, AFM, and other techniques. The results indicate polymorphic transformation of CNC proceeds gradually in a certain range of alkali concentrations, i.e. from about 8% to 12.5% NaOH. In such transition alkali concentration, cellulose I and II allomorphs coexists. Such value and range of the transition concentration is strongly interdependent with the crystallite size of CNCs. In addition, it is distinctively lower than that for macroscopic fibers (12-15% NaOH). Transmission electron microscopy and particle sizing reveals that after mercerization CNCs tend to associate. Furthermore, TEMPO-oxidized mercerized CNC reveals the morphology of individual nanocrystal of the cellulose II type, which is composed of some interconnected granular structures. Overall, this work reveals how the polymorphism and morphology of individual CNC change in alkali conditions and sheds light onto the polymorphic transition from cellulose I to II. (C) 2016 Elsevier Ltd. All rights reserved.
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