title: Assembling and redispersibility of rice straw nanocellulose: effect of tert-butanol.
abstract: Self-assembling of sulfuric-acid-hydrolyzed cellulose nanocrystals (CNCs, 6.4 nm wide) and TEMPO oxidized cellulose nanofibrils (CNFs, 2.1 nm wide) from aqueous suspensions was induced by rapid freezing (-196 °C, 10 min) and slow lyophilization (-50 °C, 0.05 mbar, 2 days). The assembled structures contain submicron (200-700 nm) wide and tens of micrometer long fibers at up to 0.1-0.5% and 0.01-0.05%, the critical fiber-to-film transformation concentrations for CNCs and CNFs, respectively. The assembled fiber widths were significantly reduced to ∼40 nm, that is, by 1 order of magnitude, when 10% of the aqueous media was replaced with tert-butanol. Further increasing tert-butanol contents in the media to 93/7 (CNCs) and 50/50 (CNFs) tert-butanol/water, both at 0.1% nanocellulose concentration, reduced longitudinal assembling for CNCs and lateral assembling for CNFs as well as increased critical fiber-to-film transformation concentration for CNFs. While all assembled structure could be redispersed in water, those from tert-butanol/water could also be easily redispersed in DMF aided with brief 2 min ultrasonication. None of the assembled structures could be redispersed in the lower dielectric constant ethanol, acetone or chloroform.
authors.affiliation: Fiber and Polymer Science, University of California , Davis, California 95616, United States.
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*; D003497:Cyclic N-Oxides / Q000737:chemistry; D005612:Freeze Drying; D018625:Microscopy, Atomic Force; D057139:Nanofibers / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D012275:Oryza / Q000378:metabolism; D010084:Oxidation-Reduction; D020002:tert-Butyl Alcohol / Q000737:chemistry*
chemical_list: D003497:Cyclic N-Oxides; D002482:Cellulose; D020002:tert-Butyl Alcohol; C003959:TEMPO
keywords: cellulose nanocrystals; cellulose nanofibrils; redispersibility; rice straw; self-assembly