Abstract Cellulose II structure was obtained when cellulose precipitated from NMMO/H 2O/cellulose solution by adding excess water. The regenerated cellulose was three times more reactive than that of untreated cellulose in hydrolysis reactions. X-ray diffraction (XRD), 13C Solid-State Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared (FTIR) Spectroscopy were used to investigate interactions between N-methylmorpholine- N-oxide (NMMO) and cellulose. Cellulose NMMO solid mixtures were heated to various temperatures and cooled to room temperature. The presence of cellulose in cellulose NMMO solid mixture decreased the NMMO melting point by 80–110 °C and hampered NMMO recrystallizing during cooling process. NMMO crystal structure collapsed between 70 and 100 °C in cellulose NMMO mixture and became very mobile (liquid like form). Mobile NMMO molecules transformed crystalline cellulose into amorphous cellulose. When the cellulose NMMO mixture was heated to 150 °C, cellulose started to replace H 2O molecules that hydrogen-bonded to NMMO. Our FTIR spectra results suggest that released H 2O molecules exist as both adsorbed H 2O molecules on cellulose and unbound H 2O molecules that are physically confined in cellulose matrix.