Triazole End-Grafting on Cellulose Nanocrystals for Water-Redispersion Improvement and Reactive Enhancement to Nanocomposites

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.