Dimethyl phosphorothioate and phosphoroselenoate ionic liquids as solvent media for cellulosic materials

A series of novel ionic liquids comprising two asymmetric phosphate-derived anions, namely dimethyl phosphorothioate and dimethyl phosphoroselenoate, and several imidazolium and non-imidazolium-based cations was prepared via a facile synthetic route. Thermal degradation was studied by dynamic thermogravimetric analysis (TGA) revealing a slightly higher stability of the imidazolium ionic liquids and an overall low thermal stability for the phosphoroselenoate salts. Long-term moisture sorption analysis showed correlation with the polarity of the cation and differences in absorption and desorption kinetics. Finally, a Eucalyptus globulus kraft paper grade pulp was dissolved and subsequently regenerated to assess the degradation of the various molecular weight fractions by size exclusion chromatography. In addition, pre-extracted xylan was subjected to the same dissolution procedure to examine the degradation of low-molecular weight components in more detail.