Facilitated fibrillation of regenerated cellulose fibers by immiscible polymer blending using an ionic liquid

Cellulose (Cell) microfibrils were prepared from regenerated Cell fibers with facilitated fibrillation character by immiscible polymer blending with polyacrylonitrile (PAN) as a minor component. The blend fibers were spun by dry-jet wet spinning of the liquid–liquid phase-separated Cell/PAN solution using the well-known ionic liquid 1-buthyl-3-methyl imidazolium chloride as a cosolvent. Wide angle X-ray diffraction, small angle X-ray scattering, and electron microscopy analyses revealed that the PAN phase in the fiber existed as an elongated island owing to the large draft force used on the spinning solutions. The PAN phase in the fiber was removed with dimethyl sulfoxide to obtain neat Cell fibers with elongated pores and nanometer-sized cross-sections. The generated pores, acting as starting points for fibrillation, allowed the lateral cohesion of the fibers to be weakened and facilitated the fibrillation tendency. Cell fibers regenerated from a 100/20 weight ratio blend of Cell/PAN were easily fibrillated to microfibrils with an average diameter of 114 ± 67 nm by mechanical treatment.