Cellulose Aerogel Microparticles via Emulsion-Coagulation Technique.

Cellulose aerogel microparticles were made via emulsification/nonsolvent induced phase separation/drying with supercritical CO2. Cellulose was dissolved in NaOH-based solvent with and without additives in order to control solution gelation. Two emulsions, cellulose solution/oil and cellulose nonsolvent/oil, were mixed to start nonsolvent induced phase separation (or coagulation) of cellulose inside each cellulose droplet leading to the formation of so-called microgels. Different options of triggering coagulation were tested, by coalescence of droplets of cellulose solution and cellulose nonsolvent and by diffusion of nonsolvent partly soluble in the oil, accompanied by coalescence. The second option was found to be the most efficient for stabilization of the shape of coagulated cellulose microgels. The influence of gelation on particle formation and aerogel properties was investigated. The aerogel particles' diameter was around a few tens of microns, and the specific surface area was 250-350 m2/g.