Synthesis and characterization of cyanoethyl hemicelluloses and their hydrated products

A novel type of hemicellulosic derivative, cyanoethyl hemicelluloses (CEH), derived from xylan-rich hemicelluloses and acrylonitriles was successfully prepared in aqueous sodium hydroxide. The reaction was performed under various reaction conditions such as temperature, time, the amount of sodium hydroxide, and the molar ratio of acrylonitrile to anhydroxylose units in hemicelluloses, and the relationship between reaction condition and DS of the CEH was investigated in detail. A series of CEH with degree of substitution of cyanoethyl (DS_C≡N) ranging from 0.23 to 1.64 were obtained. Importantly, CEH can undergo various reactions and convert into other macromolecules with functional groups like carboxylic acids, amine, aldehyde etc. In this work, H₂O₂/K₂CO₃/DMSO was used to hydrate CEH into carbamoylethyl hemicelluloses at room temperature. FT-IR, ¹H and ¹³C NMR spectra confirmed the introduction of cyanoethyl groups into the hemicelluloses backbone and the presence of carbamoylethyl groups in the hydrated product. In addition, in the nucleophilic addition reaction, the hydroxyl groups at C-3 position of the anhydroxylose units were more active than these at C-2. TGA/DTG showed that CEH had lower thermal stability than hemicelluloses. This work provided a new macromolecule which can be used as a versatile platform for producing other functional macromolecules.