Decorating aldehyde groups on the reducing end of rod-like cellulose nanocrystals provides region-selective modification for expanding diverse applications.

Modern technology has enabled the isolation of nanocellulose from plant-based fibers, and the current trend focuses on utilizing nanocellulose in a broad range of sustainable materials applications. Water is generally seen as a detrimental component when in contact with nanocellulose-based materials, just like it is harmful for traditional cellulosic materials such as paper or cardboard. However, water is an integral component in plants, and many applications of nanocellulose already accept the presence of water or make use of it. This review gives a comprehensive account of nanocellulose–water interactions and their repercussions in all key areas of contemporary research: fundamental physical chemistry, chemical modification of nanocellulose, materials applications, and analytical methods to map the water interactions and the effect of water on a nanocellulose matrix.

Different from the conventional surface modification strategy, the end reaction based on the active aldehyde groups of cellulose nanocrystal (CNC) provides a targeted modification under the protection of its surface chemistry. With the purpose of promoting its redispersibility in water, the strategy of triazole end-grafting performed on CNC was proposed in this study, exhibiting the significant improvement on the redispersion and stability of nanocrystals in the aqueous suspension attributed to synergistic effect of steric stabilization and electrostatic repulsion. The end-modified CNC was then introduced into a natural rubber (NR) matrix to fabricate the composites with reactive compatibility from a thiol–ene click reaction. Ascribed to the formation of covalent linkage between nanofillers and matrix together with the architecture of the rigid percolating network, the mechanical properties of obtained composites were remarkably advanced. With the introduction of 10 wt % end-modified CNC, the tensile strength, Young’s modulus, and storage modulus of the prepared composite increased by 160, 468, and 1041% in contrast with those of the neat NR material. More importantly, this composite retained a high level of elongation at the break (1575%) similar to that of the raw rubber material attributed to the designed covalent linkage and resultant reactive enhancement of end-modified CNCs to the NR matrix.

In addition to being a renewable nanomaterial, cellulose nanocrystals (CNCs) exhibit a high specific modulus and are widely used as a reinforcing phase (filler) to improve the mechanical performance of polymeric materials. In these composite systems, the filler–matrix, filler–filler, and matrix–matrix interactions are critical factors that govern the mechanical properties of the composites. Inspired by the idea of combining these three interactions, we design a novel composite system of reducing an end-modified CNC-enhanced thermoplastic elastomer [styrene–butadiene–styrene copolymer (SBS)] with click reaction and bulk cross-linking. The strong linkage between the nanocrystals and SBS (filler–matrix) is first achieved by the thiol–ene click reaction induced by UV irradiation in the liquid compounding process, accompanied by the preservation of surface hydroxyl groups on nanocrystals and therefore the formation of a stable percolation network (filler–filler). The matrix–matrix network is further constructed in the composite by chemical self-cross-linking of bulk SBS with a post-irradiation treatment during molding process. Benefiting from these three strong interactions, a remarkable improvement in mechanical performance is accomplished for the fabricated composite, exhibiting simultaneous increases in strength (239%), modulus (411%), work of fracture (330%), and elongation at break (7%) in comparison with those for the pure SBS material. Finally, the percolation, Halpin–Kardos, and double-network models with three interactions are applied to compare the theoretical and experimental data for mechanical properties and further discuss the enhancing mechanism for the composites.

We report a novel OPT working mode by photoelectric dual control. After each light switch, the dark current is erased by the gate voltage in depletion mode which remains unchanged during light off; the photocurrent increases by the device converting to accumulation mode when the light is on.