Cellulose nanocrystal (CNC)-based aerogels are often produced through cryo-templating, followed by either critical point drying or freeze drying. While cryo-templating gives aerogels with a bimodal pore size distribution, better morphological control may be needed for certain applications. This work compares CNC aerogels prepared using a new processing method, called pressurized gas expansion (PGX) technology, to aerogels produced via cryo-templating. In all cases, CNCs were surface-modified with orthogonal functional groups to produce covalently cross-linked aerogels which are flexible and do not disperse in water. The aerogels were imaged by scanning electron microscopy and X-ray micro-computed tomography and further characterized by nitrogen sorption isotherms, X-ray diffraction, X-ray photoelectron spectroscopy, and compression testing. PGX aerogels appeared expanded and fibrillar at high magnification, with small mesopores and macropores less than 7 µm, but with large mound-like porous aggregates. Conversely, cryo-templated aerogels were comprised of denser CNC sheets surrounding macropores of 10–950 μm. Overall, PGX aerogels had a lower density, higher porosity, and a higher specific surface area than cryo-templated aerogels; they were also less stiff due to their morphology and reduced number of chemical cross-links. Scale-up of aerogel processing and understanding of the tunability of such methods may extend the use of CNCs in applications including insulation, separations, flexible supports, drug delivery, and template materials.
CITATION STYLE
Osorio, D. A., Seifried, B., Moquin, P., Grandfield, K., & Cranston, E. D. (2018). Morphology of cross-linked cellulose nanocrystal aerogels: cryo-templating versus pressurized gas expansion processing. Journal of Materials Science, 53(13), 9842–9860. https://doi.org/10.1007/s10853-018-2235-2
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