Structure characterization of cellulose nanofiber hydrogel as functions of concentration and ionic strength
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Carboxylated cellulose nanofibers (CNFs), having an average width of 7 nm and thickness of 1.5 nm, were produced by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation method. The fiber cross-sectional dimensions were determined using small-angle X-ray scattering (SAXS), transmission electron microscopy and atomic force microscopy techniques, where the rheological properties under different concentration and ionic strength were also investigated. The formation of hydrogel was evidenced by increasing the CNF concentration or ionic strength of the solvent (water), while the gel structure in ion-induced CNF hydrogels was found to be relatively inhomogeneous. The gelation behavior was closely related to the segmental aggregation of charged CNF, which could be quantitatively characterized by the correlation length (ξ) from the low-angle scattering profile and the scattering invariant (Q) in SAXS.
KeywordsCellulose nanofibers SAXS Gelation Concentration Ionic strength
The authors would like to thank the SusChEM Program of National Science Foundation (DMR-1409507) for the financial support. The authors acknowledge the technical support of the 7.3.3 beamline in ALS, LBNL and the NG7-30 m beamline in NCNR, NIST. The authors would also like to thank Dr. Dufei Fang, Stony Brook University, for composing the ribbon model program using the software of SASView, originally developed under the NSF award DMR-0520547. In addition, L.G. would like to thank the Chinese Scholarship Council for the financial support of his overseas study in the U.S. and A.N. would like to thank the Gunnar Sundblad Foundation for supporting his study at Stony Brook University.
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