Novel insight into cellulose supramolecular structure through 13C CP-MAS NMR spectroscopy and paramagnetic relaxation enhancement

► Solvent accessibility in cellulose is evidenced and monitored through 13C T1 NMR relaxation enhancement in paramagnetic medium. ► Established NMR signal assignments for cellulose I have been confirmed. ► Existing cellulose II resonance attributions have been modified and extended. ► Novel spectral fitting routines for cellulose II have been presented. ► A model for cellulose II supramolecular structure has been established.