Investigation of the supramolecular structure of never dried bacterial cellulose

Supramolecular structure of initially wet bacterial cellulose of Acetobacter xylinum has been investigated by X-ray scattering including synchrotron radiation, transmission electron microscopy, and ¹³C-CP/MAS-NMR-spectroscopy. As a result a model is given of never dried swollen microfibrillar ribbons consisting of 5 to 12 waterfree I_α-crystalline subunits with a cross-section of about 7 nm × 13 nm and of water solvating the subunits. Lateral aggregation of these crystalline units was found along the smaller (110)-lattice planes with a layer of water between adjacent crystallites. The NMR-spectrum of wet bacterial cellulose exhibits an additional C-1 line component indicating cellulose-water interactions. During drying lateral dimensions of the microfibrillar ribbons, crystallite sizes, as well as the overall crystalline order decrease, whereas the Iα/Iβ-ratio of about 80/20 remains approximately unchanged. Conclusions were drawn with regard to the early states of structure formation of bacterial cellulose.