Dissolution and transesterification of cellulose in γ-valerolactone promoted by ionic liquids

Abstract

Cellulose dissolution is crucial for its regeneration and the application of its derivative materials. In this study, the dissolution of cellulose in γ-valerolactone (GVL), promoted by 1-ethyl-3-methylimidazolium acetate ([Emim]OAc), was investigated and 15 wt% α-cellulose was rapidly dissolved by the designed mixed organic electrolyte solvents (OESs) at 80 °C in 1 h. The rheological study indicated that the activation energy of dissolution is lower than that in pure [Emim]OAc, and the overlap concentration was determined to be C* = 1.7 wt%. The viscosity of the α-cellulose solution overlapped well with the complex viscosity, suggesting that the Cox–Merz law is valid therein. The potential of the solution for homogeneous derivatization through transesterification of α-cellulose with vinyl esters was also investigated at 80 °C in 4 h with a low vinyl ester/anhydroglucose unit (AGU) molar ratio of 3, achieving a cellulose laurate ester with a DS = 3.0, cellulose pivalate ester with a DS = 3.0 and cellulose chloroacetate ester with a DS = 1.43.