Chitin Nanowhisker Aerogels

Abstract

Chitin nanowhiskers are structured into mesoporous aerogels by using the same benign process used previously in our group to make cellulose nanowhisker aerogels. The nanowhiskers are sonicated in water to form a hydrogel before solvent-exchange with ethanol and drying under supercritical CO2 (scCO2). Aerogels are prepared with various densities and porosities, relating directly to the initial chitin nanowhisker content. scCO2 drying enables the mesoporous network structure to be retained as well as allowing the gel to retain its initial dimensions. The chitin aerogels have low densities (0.043–0.113 g cm−3), high porosities (up to 97 %), surface areas of up to 261 m2 g−1, and mechanical properties at the high end of other reported values (modulus between 7 and 9.3 MPa). The aerogels were further characterized by using X-ray diffraction, BET analysis, electron microscopy, FTIR, and thermogravimetric analysis. Characterization showed that the rod-like crystalline nature of the nanowhiskers was retained during the aerogel production process, making the aerogel truly an assembled structure of chitin nanocrystals. These aerogels also showed the lowest reported shrinkage during drying to date, with an average shrinkage of only 4 %.

Direct preparation of green and renewable aerogel materials from crude bagasse

“…Further increase of bagasse concentration to 10 % resulted in a coarse and dense upside of aerogel with pore diameter at nano-scale (Fig. 6), suggesting the extensive aggregation of bagasse, which was in (Heath et al 2013) agreement with the results from BET surface area analysis. Figure 7 were SEM images from bottom side and upside of bagasse aerogels at high magnification.…”

“…The similar results were reported in the preparation of cellulose nanowhisker aerogels (Heath and Thielemans 2010). However, the increase of bagasse concentration from 7 to 10 % led to a decrease in BET surface area from 185 to 119 m 2 / g. Because BET surface area describes the area accessible to gas adsorption and is dependent on the extent of aggregation of bagasse (Heath et al 2013), the noticeable decrease of BET surface area suggested the significant bagasse aggregation at bagasse concentration 10 %.…”

Aerogel of nitrate glycerol ether cellulose based on phase separation in acetone/ethanol mixed solvents system

“…These diffraction peaks indicated that NGEC aerogels clearly retained the crystalline structure of the NGEC. The results of SEM and XRD confirm that the NGEC gels may be formed by aggregation of the NGEC molecules, possibly induced by crystallization as a coherent bulk . In addition, the intensity of diffraction peaks at 12.98° decreases as increasing initial ethanol ratio (from NGC1 to NGC4).…”

Fabrication of porous chitin with continuous substructure by regeneration from gel with CaBr 2 ·2H 2 O/methanol

“…One of the most widely used solvent systems for chitin is a saturated CaCl 2 ·2H 2 O/methanol solution at elevated temperature [12][13][14][15] Hydrogels were then prepared by dialysis of chitin solutions with a saturated CaCl 2 ·2H 2 O/methanol, which were further converted into porous chitins by lyophilization [16,17]. As another example, a solvent exchange of chitin nanowhisker hydrogels with ethanol, followed by drying with supercritical CO 2 , yielded monolithic porous chitins with continuous substructures of porous channels [18].…”