Mechanochemical Esterification of Cellulose Nanofibers Lyophilized From Eutectic Water–tert-Butanol Mixtures (original) (raw)

Abstract

Freeze-dried CNFs can be modified by mechanochemical (MC) processes with minimal use of auxiliary solvents, however aggregation of nanofibers during lyophilization compromises their granularity and reaction efficiency. Adding 10 wt% _tert_-butanol (TBA) to aqueous slurries of wood-derived CNF creates a eutectic mixture that reduces hornification during lyophilization, resulting in well-formed aerogels with minimal shrinkage in volume. CNFs lyophilized from mixtures containing at least 10 wt% TBA exhibit an order of magnitude increase in specific surface area relative to CNFs freeze-dried from water alone. The amount of TBA and input energy needed for lyophilization can be reduced considerably by dewatering the initial CNF slurry and increasing surface-to-volume ratios during freeze drying. MC esterification of freeze-dried CNFs with hexanoic (C6), lauric (C12), stearic (C18), or oleic (OL) acid can be performed by ball milling on a horizontal tumbler at room temperature and purified by ethanol washes, with _E_-factors and process mass intensities that compare favorably against other methods of preparing organically modified CNFs. MC esterification of CNFs freeze-dried from 10 wt% TBA consistently yield higher degrees of substitution and form more stable dispersions in organic solvents than those derived from CNFs lyophilized from water.

Keywords

Nanocellulose, lyophilization, esterification, mechanochemistry, process mass intensity

Date of this Version

8-17-2023

Mavlan, Miran; Chang, Taehoo; Feng, Rudan; Wilkinson, Jake R.; Nicholas, Robert J.; Idahagbon, Nosa B.; Youngblood, Jeffrey; and Wei, Alexander, "Mechanochemical Esterification of Cellulose Nanofibers Lyophilized From Eutectic Water–tert-Butanol Mixtures" (2023). Department of Chemistry Faculty Publications. Paper 30.
https://docs.lib.purdue.edu/chempubs/30

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