Tuning morphology and properties of cellulose-based aerogels and xerogels by the introduction of tosyl moieties

Abstract Aerogels are nanostructured materials of high porosity and high specific surface area. While the first cellulose II aerogels were made about 20 years ago, practically nothing is known about the influence of the degree of substitution of cellulose ethers and esters on aerogel properties. Model hydrophobic moieties (here, tosyl) were introduced on the cellulose backbone by homogeneous derivatisation with the goal to investigate the influence of the degree of substitution (DS) on the morphology and properties of aerogels and xerogels. The materials were produced via the dissolution-coagulation route followed by drying with supercritical (sc) CO 2 (named aerogels) or low-vacuum evaporation (named xerogels). Reference materials were made from microcrystalline cellulose (MCC). The goal was to investigate how the introduction of a bulky tosyl group influences the self-assembly of polymer chains during non-solvent-induced phase separation, and to assess the impact of the DS on aerogel and xerogel properties. The DS of tosyl cellulose was varied from 0.22 to 1.26, and different non-solvents (water, ethanol, acetone) were used to test their influence on the materials’ properties. Aerogel densities ranged from 0.04 to 0.28 g/cm 3 , while xerogel densities were between 0.09 and 1.52 g/cm 3 . Drying only with sc CO 2 resulted in materials with high specific surface area, up to 360 m 2 /g. The increase in DS resulted in materials with a coarser morphology and a significant rise in hydrophobicity, as evidenced by a water contact angle reaching 130°.