Chemically and mechanically isolated nanocellulose and their self-assembled structures

• Published in: Carbohydrate polymers Vol. 95; no. 1; pp. 32 - 40
• Main Authors: Jiang, Feng, Hsieh, You-Lo
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 05-06-2013; Elsevier
• Subjects: acid hydrolysis; Agronomy. Soil science and plant productions; Applied sciences; Biological and medical sciences; cellulose; Cellulose - chemistry; Cellulose and derivatives; Cellulose Iβ; Cellulose nanocrystals; Cellulose nanofibrils; Crystallization; Cyclic N-Oxides - chemistry; Exact sciences and technology; Freeze Drying; Freezing; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Hydrolysis; Microscopy, Atomic Force; Microscopy, Electron, Scanning; Microscopy, Electron, Transmission; nanocrystals; nanofibers; Nanofibers - chemistry; Nanofibers - ultrastructure; Nanoparticles - chemistry; Nanoparticles - ultrastructure; Natural polymers; Oryza; oxidation; Oxidation-Reduction; Physicochemistry of polymers; Rice straw; Self-assembly; Spectroscopy, Fourier Transform Infrared; sulfates; sulfuric acid; Sulfuric Acids - chemistry; Use of agricultural and forest wastes. Biomass use, bioconversion; X-Ray Diffraction; Self-assembly; Cellulose nanofibrils; Cellulose Iβ; Cellulose nanocrystals; Rice straw; Self assembly; Cellulose; Chemical isolation; Sodium Hypochlorites; Mechanical treatment; Piperidine derivatives; Electrokinetic potential; Oxidation; Agricultural waste; Nanocrystal; Nanomaterial synthesis; Freeze drying; Crystallinity; Chemical degradation; Experimental study; Rice by product; Hydrolysis; Morphology; Defibrillation; Aqueous dispersion
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2013.02.022

► Cellulose nanocrystals and nanofibrils isolated from rice straw yielded up to 20%. ► Isolation by acid hydrolysis, blending and TEMPO oxidation was compared. ► Nanocellulose showed distinctly different sizes and surfaces. ► Nanocellulose had cellulose Iβ crystalline structure with crystallinity up to 91%. ► Nanocellulose self assembled into 153–440nm fibers upon rapid freezing and drying.
Cellulose nanocrystals (CNCs) and nanofibrils (CNFs) have been isolated from pure rice straw cellulose via sulfuric acid hydrolysis, mechanical blending and TEMPO-mediated oxidation to 16.9%, 12% and 19.7% yields, respectively. Sulfuric acid hydrolysis produced highly crystalline (up to 90.7% CrI) rod-like (3.96–6.74nm wide, 116.6–166nm long) CNCs with similarly negative surface charges (−67 to −57mV) and sulfate contents but decreasing yields and dimensions with longer hydrolysis time. Mechanical defibrillated CNFs were 82.5% crystalline and bimodally distributed in sizes (2.7nm wide and 100–200nm long; 8.5nm wide and micrometers long). TEMPO mediated oxidation liberated the most uniform, finest (1.7nm) and micrometer long, but least crystalline (64.4% CrI) CNFs. These nanocellulose self-assembled into submicron (153–440nm wide) fibers of highly crystalline (up to 90.9% CrI) cellulose Iβ structure upon rapid freezing (−196°C) and freeze-drying. The self-assembling behaviors were analyzed based on nanocellulose dimensions, specific surfaces and surface chemistries.