Stable nanocellulose gels prepared by crosslinking of surface charged cellulose nanofibrils with di- and triiodoalkanes

摘要

Nanocellulose gels were prepared by a new chemical crosslinking approach. Carboxy group containing cellulose nanofibrils, which were prepared by (2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl (TEMPO) mediated oxidation, were reacted with two different diiodoalkanes and one triiodoalkane in DMSO/water dispersions at elevated temperatures. Mechanically stable gels were obtained that were characterized with respect to chemical and physical properties. It was confirmed by FTIR spectroscopy that crosslinking of TEMPO oxidized cellulose nanofibrils (TCNF) occurs by the formation of ester bonds. The kinetics of gel formation were evaluated by oscillatory rheology experiments. For long alkyl chain cross-linkers, namely 1,4-diiodobutane and 1,10-diiododecane, the initial gel was formed within a short time (gel point < 5 min) and further evolved upon time for about 0.5-2 h. For the short crosslinker triiodomethane, gel formation was slower and resulted in lower mechanical strength. Graphic abstract