Synthesis and spectroscopic analysis of cellulose sulfates with regulable total degrees of substitution and sulfation patterns via ~(13)C NMR and FT Raman spectroscopy

摘要

Synthesis and spectroscopic characterisation of cellulose sulfate (CS) were reported. Various CS exhibiting diverse degrees of sulfation (DS_S) were prepared through acetosulfation or direct sulfation of cellulose. During the acetosulfation, intermediate product - cellulose acetate sulfate (CAS) - was formed after the comparative esterification and subsequent deacetylation of CAS led to CS. The direct sulfation proceeded quasi-homogeneously and heterogeneously in N,N-dimethylformamide (DMF) or homogeneously in N,N-dimethylacetamide (DMAc)/LiCl mixture. The total DS_S between 0.21-2.59 and partial DS_(S6) as well as DS_(S2) of up to 1 were determined via elemental analysis and ~(13)C NMR spectroscopy. Besides, solid-state CP/MAS ~(13)C NMR could characterise CS regarding the sulfation. Subsequently, FT Raman investigation of obtained CS was conducted with the aim to establish analysis methods quantifying the total DS_S. The intensities of Raman bands ascribed to the vibrations of OSO and C-O-S groups were used as analysis parameters, yielding calibration curves with high correlation coefficients of more than 0.96.