Cationization of lignocellulosic fibers with betaine in deep eutectic solvent: Facile route to charge stabilized cellulose and wood nanofibers

Abstract

In this study, a deep eutectic solvent (DES [based on triethylmethylammonium chloride (TEMA) and imidazole]) was used as a reaction medium for cationization of cellulose fibers with trimethylglycine (betaine) hydrochloride in the presence of p-Toluenesulfonyl (tosyl) chloride. Cellulose betaine ester with a cationic charge up to 1.95 mmol/g was obtained at mild reaction conditions (four hours at 80 °C). The reaction was further demonstrated in the fabrication of cationic cellulose nanofibers (CCNFs) by a mild mechanical disintegration of cationized cellulose. In addition to CCNFs, cationic wood nanofibers (CWNFs) were produced directly from groundwood pulp (GWP) with a high lignin content (27 w%). Individualized CCNFs and CWNFs had a fiber diameter of 4.7 ± 2.0 and 3.6 ± 1.3 nm, respectively, whereas some larger fiber aggregates (diameter below 200 nm) were also observed, especially in the case of CWNFs.