Structural changes during heterogeneous sulfation and following homogenization of cotton cellulose

We used to consider native cellulose to be composed of microfibrils continuously crystalline along the chain direction with constant lateral dimension. To sulfate the surface of cellulose microfibrils, we activated cotton fibers by pre-swelling in water or DMF followed by immersion in an excess amount of sulfamic acid in dimethylformamide (DMF) in heterogeneous conditions. The degree of sulfation was followed by elemental analysis and conductometric titration, while the structural changes associated with the sulfation and the homogenization were investigated by infrared spectroscopy, solid-state NMR, and X-ray diffraction. The initial sulfation of the cellulose surface was well described as a first order reaction with a kinetic constant of 2 × 10 ^-3 s ^-1 at 80 °C using 3.6