Preparation of sodium cellulose sulfate oligomers by free-radical depolymerization

Sodium cellulose sulfates with various degree of substitution (DS) and degree of polymerization (DP) were synthesized by homogeneous sulfation of cellulose with different DP by using SO3/pyridine (Py) complex in N,N-dimethylacetamide/lithium chloride (DMA/LiCl). Sodium cellulose sulfate (SCS) samples obtained were free-radically depolymerized with hydrogen peroxide and copper (II) acetate at a controlled pH value of 7.5–8.0 and without control of the pH value (pH 2.5–4.0). The depolymerization process was studied with respect to changes in molecular mass, total DS, and substituent distribution of SCS. Elemental analysis, 13C NMR- and IR spectroscopic methods indicated that primary structures of SCS were retained with insignificant decreases in total sulfate content in the depolymerization. The depolymerization of SCS was randomly and obeyed pseudo first order kinetics under the conditions applied. SCS oligomers with low DP and very narrow molecular weight distribution were prepared by the depolymerization at pH 2.5–4.0.