1. Visualizing Degradation of Cellulose Nanofibers by Acid Hydrolysis
- Author
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Muhammad Awais, Timo Pääkkönen, Panagiotis Spiliopoulos, Eero Kontturi, Leena Pitkänen, Stefan Spirk, Kirsi Svedström, Mira Viljanen, Materials Chemistry of Cellulose, Graz University of Technology, Department of Bioproducts and Biosystems, University of Helsinki, Aalto-yliopisto, and Aalto University
- Subjects
Polymers and Plastics ,Nanofibers ,Bioengineering ,02 engineering and technology ,010402 general chemistry ,order/disorder transitions ,01 natural sciences ,Article ,Nanocellulose ,Biomaterials ,chemistry.chemical_compound ,Crystallinity ,Hydrolysis ,X-Ray Diffraction ,cellulose degradation ,Materials Chemistry ,Cellulose ,nanocellulose ,Molar mass ,atomic force microscopy ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Cellulose fiber ,chemistry ,Chemical engineering ,Nanofiber ,Nanoparticles ,Acid hydrolysis ,0210 nano-technology - Abstract
Cellulose hydrolysis is an extensively studied process due to its relevance in the fields of biofuels, chemicals production, and renewable nanomaterials. However, the direct visualization of the process accompanied with detailed scaling has not been reported because of the vast morphological alterations occurring in cellulosic fibers in typical heterogeneous (solid/liquid) hydrolytic systems. Here, we overcome this distraction by exposing hardwood cellulose nanofibers (CNFs) deposited on silica substrates to pressurized HCl gas in a solid/gas system and examine the changes in individual CNFs by atomic force microscopy (AFM). The results revealed that hydrolysis proceeds via an intermediate semi-fibrous stage before objects reminiscent of cellulose nanocrystals were formed. The length of the nanocrystal-like objects correlated well with molar mass, as analyzed by gel permeation chromatography, performed on CNF aerogels hydrolyzed under identical conditions. Meanwhile, X-ray diffraction showed a slight increasein crystallinity index as the hydrolysis proceeded. The results provide a modern visual complement to >100 years of research in cellulose degradation.
- Published
- 2021