Homogeneous cyanoethylation of cellulose with acrylonitrile in a CO2 switchable solvent

Abstract

Development of an anhydrous homogeneous method for the cyanoethylation of cellulose is highly desirable. In this study, a series of cyanoethyl cellulose (CEC) composites were homogeneously prepared via the Michael addition of acrylonitrile (AN) to the activated hydroxyl group of cellulose in a novel CO₂ switchable solvent. The cellulose was dissolved in this solvent generating a nucleophilic cellulose carbonate intermediate, which is able to react with AN directly via Michael addition and results in CEC with a tunable degree of substitution (DS) by varying reaction conditions, such as temperature, reaction time, and the feeding ratio of acrylonitrile. The obtained CEC samples have DS values ranging from 0.12 to 1.03. The solubility of the CEC samples varies with DS values. This organic and anhydrous CO₂ switchable solvent system enables the preparation of CEC with high quality without side reactions induced by water and much easier down-stream treatment, which is superior to other homogeneous counterparts. This study suggests a new platform for the synthesis of novel cellulose derivatives by Michael addition in the CO₂ switchable solvent system in the future.