One-Component Nanocomposites Based on Polymer-Grafted\nCellulose Nanocrystals

Abstract

Cellulose\nnanocrystals (CNCs) are widely used as reinforcing fillers\nin polymers due to their exceptionally high stiffness and strength\nand because the biological species from which they are isolated represent\nrenewable resources. However, aggregation of the CNCs, which is concomitant\nwith limited reinforcement, is often difficult to avoid. One-component\nnanocomposites (OCNs) based on polymer-grafted nanoparticles can solve\nthis problem because this approach affords, by design, materials in\nwhich no such aggregation is possible. At the same time, chain entanglements\nbetween the CNC-grafted polymer chains provide stress transfer among\nthe particles. To demonstrate this, we investigated OCNs based on\npolymethacrylate-grafted CNCs. A previously unaccessed compositional\nspace, that is, OCNs with a CNC content of 10 or 20 wt %, was explored.\nCotton linter-based CNCs were modified via surface-photoinitiated\nfree radical polymerization, which involved the functionalization\nof the CNC surfaces with benzophenone moieties as photoradical initiator\nspecies and the subsequent surface-photoinitiated polymerization of\nmethyl or hexyl methacrylate under UV irradiation at 365 nm. The resulting\nparticles readily dispersed in THF. Solvent-casting and compression-molding\nafforded films of homogeneous appearance, which display remarkable\nimprovements in stiffness or toughness and strength in comparison\nto conventional two-component nanocomposites of unmodified CNCs and\nthe respective polymers.