Theoretical study on the cross-linking reaction mechanism of cellulose nanofibrils initiated by fluorine

Theoretical investigation on the cross-linking reaction process and mechanism of cellulose nanofibrils (CNFs) initiated by fluorine is accomplished by density functional theory. Three reaction pathways generated aldehyde and ester are identified. The reaction potential energy information of the ten reaction channels at B3LYP/6-311+G(d,p) level are obtained. The calculation results show that the reaction pathway of forming ester thereafter acyl fluoride has realized the cross-linking of cellulose. The reaction pathway of forming ester is more kinetically and thermodynamically favorable than the others of forming aldehyde with the lower energy barriers. The oxidation site mainly occurred at the methylene hydrogen of the hydroxymethyl group in the cellulose. The cross-linking of two cellulose molecules initiated by fluorine forming a covalent ester bond would be beneficial to improve cellulose mechanical properties of the insulating paper, which is better to add cellulose nanofibrils served as a “bridge” for strengthening the connection between celluloses.