• Liebner, Falk

Abstract

<jats:title>Abstract</jats:title> <jats:p>Lightweight cellulose II aerogels featuring densities of about 40–70 mg cm<jats:sup>−3</jats:sup> were prepared from 1 to 3% solutions of different pulps in hot (60°C) tetra-n-butylammonium fluoride (TBAF)·H<jats:sub>2</jats:sub>O/dimethyl sulfoxide (DMSO) by (i) the coagulation of cellulose with EtOH to afford self-standing, transparent and homogeneous gels, (ii) gel ripening and washing, (iii) solvent exchange and (iv) supercritical carbon dioxide (scCO<jats:sub>2</jats:sub>) drying. Size exclusion chromatography (SEC) analyses confirmed that the chemical integrity of cellulose is largely preserved at short dissolution times. Dissolution of more than 2% of cellulose at a sufficiently low viscosity for solution, casting was achieved after the water content of TBAF was reduced to a value equaling that of the monohydrate. Intriguingly, the obtained aerogels featured higher specific surfaces (≤470 m<jats:sup>2</jats:sup> g<jats:sup>−1</jats:sup>) than comparable materials prepared from other cellulose solvents. This is due to the particular morphology of TBAF aerogels, which is supposedly formed by spinodal decomposition of the cellulose/solvent mixture upon exposure to the cellulose antisolvent. As a result, largely homogeneous three-dimensional (3D) networks of agglomerated cellulose spheres were formed, which simultaneously acted as supporting scaffolds for interconnected micron-size voids. As cellulose spheres are composed of very small interwoven nanofibers, TBAF-derived aerogels contain a high portion of micropores and small amounts of mesopores, too.</jats:p>

Topics

• impedance spectroscopy
• morphology
• surface
• Carbon
• spinodal decomposition
• viscosity
• casting
• void
• cellulose
• size-exclusion chromatography
• drying
• washing