Vapour-induced phase transformation in ultrathin cellulose films

The structural transformation of thin amorphous cellulose films in water and organic solvent vapour has been studied using grazing-incidence X-ray diffraction and atomic force microscopy. Amorphous cellulose films transform to cellulose II upon exposure to water vapour, and cellulose IV_II in the dimethyl sulfoxide (DMSO) vapour. The anisotropy in crystalline orientation has developed during the vapour exposure, due both to the surface and confinement effects in thin film geometry. The findings imply a novel route of the vapour treatment of cellulose films to obtain unique structures.