Polymer grafting on cellulose nanocrystals initiated by ceric ammonium nitrate: is it feasible under acid-free conditions?

Key Words:COPOLYMERIZATION; NANOCOMPOSITES; EMULSION

Abstract:It is of great significance to tailor the physicochemical properties of cellulose nanocrystals (CNCs) for broadening their application fields. Grafting polymerization initiated by cerium ammonium nitrate (CAN) in aqueous medium is a facile and efficient surface modification strategy for CNCs. However, CAN is generally used under strong acidic conditions to prevent hydrolysis; strong acids cause severe environmental problems and limit the monomer species of the candidate. Herein, an acid-free polymer grafting modification method initiated by CAN for carboxylated CNCs (CCNCs) was reported. For CCNCs, a high monomer conversion rate (>80%) and grafting yield (>200%) were obtained even at pH=7 when methyl methacrylate (MMA) was used as the monomer. It is worth noting that the time-consuming dialysis process for CNCs was not required before the grafting reaction, and the CNCs-g-PMMA can be "self-purified" due to its spontaneous precipitation from water. Moreover, the initiator's consumption in this system is very low (1.82 mmol L-1) compared with previously reported values. By investigating the interaction between CAN and CCNCs and the effect of CCNCs on the hydrolysis of CAN, it is revealed that a CCNC complex with Ce4+ acts as the "macromolecular initiator" to initiate the grafting polymerization under acid-free conditions. This work overcomes the limitation of strong acidic conditions for the polymer grafting modification of CNCs initiated by CAN and is conducive to the industrial production of polymer-grafted CNCs under environmentally friendly conditions.

Volume:23

Issue:21

Translation or Not:no