Ultrasound-assisted dissolution of cellulose in ionic liquid

Ultrasound-assisted dissolution of cellulose was performed in ionic liquid 1-butyl-3-methylimidazolium chloride ([C4mim]Cl). The dissolution process was monitored with polarizing microscope. The effects of parameters including ultrasonic power and irradiation time on cellulose dissolution time were investigated. The dissolution time required for complete dissolution decreased from 190 min without assistance to 60 min irradiated with 30 W ultrasound for 20 min. The regenerated cellulose samples were characterized with FT-IR, solid-state CP/MAS 13C NMR, wide-angle X-ray diffraction and thermal analysis. The results showed that most crystalline structure of cellulose was destroyed to amorphous structure, and the remained crystalline structure of cellulose was converted to cellulose II from cellulose I in native cellulose. After dissolution and regeneration in ionic liquid, the thermal stability of cellulose decreased and the pyrolysis residues increased.