Direct sulfation of bacterial cellulose with a ClSO3H/DMF complex and structure characterization of the sulfates

Bacterial cellulose (BC) is a form of cellulose synthesized by microorganisms, which has unique structure properties and differs from plant cellulose. Up to now, chemical modification of BC has not been studied widely. This paper aims to prepare sodium bacterial cellulose sulfate (SBS) in N,N‐dimethylformamide (DMF) with a ClSO3H/DMF complex as the sulfating agent. SBSs with diverse degree of sulfation (DS, 0.04–0.86) were synthesized. The system could change from heterogeneous to homogeneous during the sulfation. Regarding to the DS, the optimal ClSO3H amount and reaction time were 6 mol/mol anhydroglucose unit and 4 h, respectively. DS increased a little when increasing the temperature, while the yield decreased significantly. SBSs with DS > 0.24 were soluble in deionized water. Carbon nuclear magnetic resonance spectroscopy revealed that the sulfation prefers to take place in the order of C‐6 > C‐2 > C‐3. The X‐ray diffraction profiles indicated that the crystalline structure of BC was destroyed during sulfation. BC has better reactivity than microcrystalline cellulose in both sulfation and depolymerization processes. SBS is a potential biomaterial. However, BC depolymerized obviously in present sulfation, which forbids application of SBS in material. Moisture of the reaction mixture should be removed as completely as possible to guarantee efficient sulfation and decrease depolymerization. Copyright © 2013 John Wiley & Sons, Ltd.