Preparation of cellulose microparticles having hierarchical internal structures from multiple emulsion templates

Microparticles having porous walls composed of nanofibers of cellulose were prepared from water-in-oil emulsion templates. This was achieved by emulsifying hot solutions of cellulose in a saturated aqueous solution of Ca(SCN)2 in decane in the presence of sorbitan monooleate as an emulsifier. Cooling the emulsion induced micro-phase separation within droplets of the cellulose solution, during which a three-dimensional network of cellulose nanofibers was formed and solidified the droplets. The particles size could be controlled by changing emulsification conditions such as stirring rate, the amount of emulsifier, and the volume ratio between the cellulose solution and decane. We found multiple emulsions (O/W/O and W/O/W/O emulsions) were formed when high amounts (>40 vol%) of the cellulose solution were emulsified. Particles obtained from the multiple emulsions had unique hierarchical internal structures, including a hollow particle with nanofibrous walls and particles-in-particle type structures where multiple porous particles are contained within a particle. [Display omitted]