Cellulose is a ubiquitous natural fiber used in various industrial materials and applications. We prepared micron-sized cellulose particles by the solvent releasing method (SRM) in which cellulose-[Bmim]Cl-N,N-dimethylformamide (DMF) droplets are dispersed in hexadecane (HD) containing dissolved surfactant. The dispersion is then poured into a large amount of 1-butanol. Since 1-butanol is miscible with HD, [Bmim]Cl, and DMF but not with cellulose, the cellulose particles precipitate out. FTIR and (1)H NMR analyses confirmed that this technique precipitated cellulose and completely removed [Bmim]Cl and DMF from the cellulose-[Bmim]Cl-DMF droplets. Interestingly, the obtained cellulose particles were almost the same size as the original droplets (cellulose, 7 wt%), indicating a microporous structure of the cellulose particles with a large medium content. Although the microporous structure collapsed as the medium evaporated, it was maintained by a freeze-drying technique.

We have reported cellulose particles with a spongy structure that we prepared by the solvent releasing method (SRM) from cellulose droplets composed of cellulose, 1-butyl-3-methylimidazoliumchrolide ([Bmim]Cl), and N,N-dimethylformamide (DMF). The spongy structure collapsed as the medium evaporated, resulting in dense cellulose particles. In this study, we encapsulated the hydrophilic and hydrophobic fluorescent substances in these particles to investigate the use of such particles in potential applications that require encapsulating of substances (e.g., drug delivery). Wet cellulose particles retained their spongy structure in both hydrophobic and hydrophilic media. When the spongy cellulose particles were dispersed in a solution containing nonvolatile solutes, these solutes were driven into the cellulose particles as media evaporated. Subsequently, the cellulose particles collapsed and encapsulated the nonvolatile solutes. Regardless of whether the solute was hydrophilic or hydrophobic, the encapsulation efficiency exceeds 80%. The maximum loading reflected the saturated solubility of solute in solution that filled the cellulose beads. Moreover, the encapsulated solute was released by dispersing the cellulose beads in the solvent, and the rate of release of the encapsulated solute could be controlled by coating the cellulose beads with a conventional polymer.

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