Characteristics of sulfated and carboxylated cellulose nanocrystals extracted from Juncus plant stems

Abstract

In this study, sulfated and carboxylated cellulose nanocrystals (CNC) have been produced from newly identified cellulose-rich bio-sourced material, namely Juncus plant. The Juncus plant stems were firstly subjected to chemical treatments to produce purified cellulose microfibers (CMF) with an average diameter of 3.5 µm and yield of 36%. By subjecting CMF to sulfuric and citric/hydrochloric mixture acids hydrolysis, sulfated CNC (S-CNC) and carboxylated CNC (C-CNC) have been produced with a diameter of 7.3 ± 2.2 and 6.1 ± 2.8 nm, and a length of 431 ± 94 and 352 ± 79 nm, respectively. These newly extracted S-CNC and C-CNC exhibited a crystallinity of 81% and 83% with cellulose I structure and showed high thermal stability (>200 °C). Herein, this newly identified Juncus plant, which is a naturally-derived source, could be used as a valuable alternative to conventional sources such as wood and cotton for nanocellulose production. We speculate that the determined high thermal stability, the large aspect ratio and high crystallinity will allow the use of the extracted CNC as nano-reinforcing agents in polymers that require processing temperatures of up to 200 °C. Owing to their surface functionalities (sulfated or carboxylated surface groups), the here produced CNC could be used as nano-additives or nano-reinforcing agents for water-soluble bio-polymers in order to produce bio-nanocomposites by solvent casting techniques.

Keywords: Acid hydrolysis; Cellulose nanocrystals; Juncus plant stems.