Synthesis and characterisation of cellulose sulfates regarding the degrees of substitution, degrees of polymerisation and morphology

Abstract

The synthesis and characterisation of cellulose sulfates were reported. Various cellulose sulfates with diverse degrees of substitution ascribed to sulfate groups (DSS) between 0.21 and 2.59 were prepared through acetosulfation or direct sulfation of two celluloses. The number-average degrees of polymerisation (DPn) of these cellulose sulfates were determined to be in the range of 59 and 232 via size exclusion chromatography (SEC). Accordingly, the molecular weight of cellulose was remarkably decreased during the sulfation. The use of high amount of sulfating agent and high sulfation temperature led to stronger reduction of the DPn in comparison to low amount of sulfating agent and low temperature. The morphology of cellulose sulfate was analysed via scanning electron microscopy (SEM) and wide-angle X-ray diffraction (WAXD). Obtained cellulose sulfates demonstrated different surface properties from cellulose and became more amorphous than starting celluloses.