On account of their intriguing mechanical properties, low cost, and renewable nature, high-aspect-ratio cellulose nanocrystals (CNCs) are an attractive component for many nanomaterials. Due to hydrogen bonding between their surface hydroxyl groups, unmodified CNCs (H-CNCs) aggregate easily and are often difficult to disperse. It is shown here that on account of ionic repulsion between charged surface groups, slightly phosphorylated CNCs (P-CNCs, average dimensions 31 ± 14 × 316 ± 127 nm, surface charge density = 10.8 ± 2.7 mmol/kg cellulose), prepared by controlled hydrolysis of cotton with phosphoric acid, are readily dispersible and form stable dispersions in polar solvents such as water, dimethyl sulfoxide, and dimethylformamide. Thermogravimetric analyses reveal that these P-CNCs exhibit a much higher thermal stability than partially sulfated CNCs (S-CNCs), which are frequently employed, but suffer from limited thermal stability. Nanocomposites of an ethylene oxide-epichlorohydrin copolymer and H-CNCs, S-CNCs, and P-CNCs were prepared, and their mechanical properties were studied by dynamic mechanical thermal analysis. The results show that P-CNCs offer a reinforcing capability that is comparable to that of H-CNCs or S-CNCs.

Cellulose nanocrystals (CNCs) are widely used as reinforcing filler in polymers, due to their exceptionally high stiffness and strength and because the biological species from which they are isolated represent renewable resources. However, aggregation of the CNCs, which is concomitant with limited reinforcement, is often difficult to avoid. One-component nanocomposites (OCNs) based on polymer-grafted nanoparticles can solve this problem, because this approach affords, by design, materials in which no such aggregation is possible.At the same time, chain entanglements between the CNC-grafted polymer chains provide stress-transfer among the particles. To demonstrate this, we investigated OCNs based on polymethacrylate-grafted CNCs. A previously un-accessed compositional space, i.e., OCNs with a CNC content of 10 or 20 wt%, was explored. Cotton linter-based CNCs were modified via surface-photoinitiated free radical polymerization, which involved the functionalization of the CNC surfaces with benzophenone moieties as photo-radical initiator species, and the subsequent surface-photoinitiated polymerization of methyl or hexyl methacrylate under UVirradiation at 365 nm. The resulting particles readily dispersed in THF. Solvent-casting and compression-molding afforded films of homogeneous appearance, which display remarkable 2 improvements in stiffness or toughness and strength in comparison to conventional twocomponent nanocomposites of unmodified CNCs and the respective polymers.Polymer-grafted CNCs can be synthesized via "grafting-from", "grafting-to", or "graftingthrough" approaches involving functional groups on the CNCs surface. 3,32 The grafting-from approach, which was utilized here, involves the functionalization of the CNCs with polymer brushes by way of surface-initiated polymerization from initiator groups immobilized on the NPs' surface. This framework generally leads to polymer grafts with a well-controlled length and high polymer grafting density. 3 The first example of OCNs based on polymer-grafted CNCs, using a grafting-from approach, was reported by Chen et al., 7 who functionalized CNCs with semicrystalline poly(ε-caprolactone) via surface-initiated ring-opening polymerization.OCNs with a CNC content of between 4 and 8 wt% proved to be melt-processable and the authors reported a non-linear dependence between the CNC content and the OCN mechanical properties. Unfortunately, no comparison with conventional composites was made and no correlation between the PCL graft structure and the properties of the OCNs could be established. In another study, Chang et al. reported the synthesis of CNCs-g-poly(ethynylenefluorene) through Sonogashira coupling via a grafting-from approach, 8 but the mechanical properties of the material were not investigated.Here, we report the synthesis of amorphous, polymethacrylate-grafted CNCs through a synthetically undemanding free radical polymerization protocol. It involves the surface functionalization of CNCs with a benzophenone derivative that serves as radical photoinitiator f...

Biodegradable polyester urethane acrylate oligomers were created to address the scarcity of resins for Digital Light Processing (DLP). Cell adhesion was heavily influenced by copolymer composition.