Absorbent Filaments from Cellulose Nanofibril Hydrogels through Continuous Coaxial Wet Spinning.

A continuous and scalable method for the wet spinning of cellulose nanofibrils (CNFs) is introduced in a core/shell configuration. Control on the interfacial interactions was possible by the choice of the shell material and coagulant, as demonstrated here with guar gum (GG) and cellulose acetate (CA). Upon coagulation in acetone, ethanol, or water, GG and CA formed supporting polymer shells that interacted to different degrees with the CNF core. Coagulation rate was shown to markedly influence the CNF orientation in the filament and, as a result, its mechanical strength. The fastest coagulation noted for the CNF/GG core/shell system in acetone led to an orientation index of ∼0.55 (Herman's orientation parameter of 0.40), Young's modulus of ∼2.1 GPa, a tensile strength of ∼70 MPa, and a tenacity of ∼8 cN/tex. The system that underwent the slowest coagulation rate (CNF/GG in ethanol) displayed a limited CNF orientation but achieved an intermediate level of mechanical resistance, owing to the strong core/shell interfacial affinity. By using CA as the supporting shell, it was possible to spin CNF into filaments with high water absorption capacity (43 g water/g dry filament). This was explained by the fact that water (used as the coagulant for CA) limited the densification of the CNF core structure, yielding filaments with high accessible area and pore density.

Furan-modified natural rubber: A substrate for its reversible crosslinking and for clicking it onto nanocellulose.

The conventional vulcanization process applied to elastomers is irreversible and hinders therefore their useful recycling. We demonstrate here that natural rubber can be reversibly crosslinked via the Diels-Alder coupling of furan and maleimide moieties. The furan-modified natural rubber used in this strategy was also exploited to bind it to maleimide-modified nanocellulose, thus generating a covalently crosslinked composite of these two renewable polymers.

Preparation of highly hydrophobic and lipophobic cellulose fibers by a straightforward gas-solid reaction.

This work describes a very simple, rapid, and efficient approach to the hydrophobization and lipophobization of cellulose fibers through their reaction with gaseous trichloromethylsilane (TCMS). The characterization of the modified surface involved FTIR-ATR and solid-state (29)Si NMR spectroscopy, scanning electron microscopy (SEM), and contact angle measurements with different liquids. The modification generated an inorganic coating around the fibers, associated with the construction of a three-dimensional network of Si-O-Si bridges partly bound to the polysaccharide macromolecules. This coating conferred both a high hydrophobicity and a lipophobicity to the samples even when the treatments applied modest TCMS quantities and reaction times as short as 30 s. The green connotation of this novel process constitutes an additional positive feature.