title: Chemically and mechanically isolated nanocellulose and their self-assembled structures.
abstract: 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 (3.96-6.74 nm wide, 116.6-166 nm long) CNCs with similarly negative surface charges (-67 to -57 mV) and sulfate contents but decreasing yields and dimensions with longer hydrolysis time. Mechanical defibrillated CNFs were 82.5% crystalline and bimodally distributed in sizes (2.7 nm wide and 100-200 nm long; 8.5 nm wide and micrometers long). TEMPO mediated oxidation liberated the most uniform, finest (1.7 nm) and micrometer long, but least crystalline (64.4% CrI) CNFs. These nanocellulose self-assembled into submicron (153-440 nm 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.
authors.affiliation: Fiber and Polymer Science, University of California, Davis, CA 95616, USA.
authors.forename: Feng
authors.initials: F
authors.lastname: Jiang
authors.forename: You-Lo
authors.initials: YL
authors.lastname: Hsieh
mesh_terms: D002482:Cellulose / Q000737:chemistry*; D003460:Crystallization; D003497:Cyclic N-Oxides / Q000737:chemistry; D005612:Freeze Drying; D005615:Freezing; D006868:Hydrolysis; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D057139:Nanofibers / Q000737:chemistry* / Q000648:ultrastructure; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D012275:Oryza; D010084:Oxidation-Reduction; D017550:Spectroscopy, Fourier Transform Infrared; D013464:Sulfuric Acids / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D003497:Cyclic N-Oxides; D013464:Sulfuric Acids; D002482:Cellulose; C033158:sulfuric acid; C003959:TEMPO