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Influence of the supramolecular structure of thin films of more crystalline cellulose (left) and highly amorphous cellulose (middle) on water vapour induced behaviour (right).

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Phosphorylated cellulosic micro(nano)fibrillated materials are increasingly considered for flame-retardant applications as a biobased alternative to their halogen-based counterparts. Most of the reported cellulose functionalization strategies, however, are realized at low solids contents and/or involve energy-intensive fiber disintegration methods. In this perspective, we propose an alternative concept of phosphorylated microfibrillated cellulose production with notably high (25 wt %) solids content and low (0.6 MWh/t) energy consumption. Here, an enzyme-aided pulp disintegration upon mild mechanical treatment was combined with an effective mixing of the fibrillated material with (NH 4 ) 2 HPO 4 in the presence of urea. Subsequently, the obtained slurry was cured at elevated temperature to enable cellulose phosphorylation, which was redispersed afterward in water. The morphology of the obtained phosphorylated micro(nano)fibrillated cellulose materials was extensively characterized by optical microscopy, a fiber analyzer, SEM, and AFM. The presence of phosphate groups in the cellulose structure was validated by ATR-FTIR as well as 31 P and 13 C NMR spectroscopy. The casted films prepared from phosphorylated cellulose bearing a charge of 1540 μmol/g, which was the highest among the prepared samples, demonstrated noticeably improved flame retardancy, leaving ∼89% of the material after burning as well as selfextinguishing properties when the samples were subjected to a butane flame for 3 s.

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The exploitation of the effortless self‐assembly behavior of biomass‐based bricks can be seen as a promising route toward the innovative architectures. Here, a straightforward approach is presented where carbohydrate‐based diblock copolymer, polystyrene‐block‐maltoheptaose (PS‐b‐MH), is organized either on a rigid ultrathin film or on a flexible self‐standing film of wood‐derived cellulose nanofibrils (CNFs). During solvent annealing PS‐b‐MH deposited on relatively rough CNF film undergoes spontaneous rearrangement into high‐resolution patterns with a diblock domain spacing of 10–15 nm. The ideal conditions the self‐assembly require weak interactions between block copolymer and the substrate to increase the chain mobility and enable rearrangements. This is exactly how the system behaves. Adsorption studies of PS‐b‐MH on CNF surfaces reveal weak interactions, and the formed PS‐b‐MH layer is soft and mobile. Even the appearance of more challenging vertical orientation formed on smooth CNF substrates is tentatively evidenced by grazing‐incidence small‐angle X‐ray scattering and atomic force microscope indicating favorable surface interactions between CNF and PS‐b‐MH.

Oil-in-water emulsions stabilized using cellulose nanofibrils (CNF) form extremely stable and high-volume creaming layers which do not coalesce over extended periods of time. The stability is a result of the synergistic action of Pickering stabilization and the formation of a CNF percolation network in the continuous phase. The use of methyl cellulose (MC) as a co-emulsifier together with CNF further increases the viscosity of the system and is known to affect the droplet size distribution of the formed emulsion. Here, we utilize these highly stable creaming layer systems for in situ polymerization of styrene with the aim to prepare an emulsion-based dope for additive manufacturing. We show that the approach exploiting the creaming layer enables the effortless water removal yielding a paste-like material consisting of polystyrene beads decorated with CNF and MC. Further, we report comprehensive characterization that reveals the properties and the performance of the creaming layer. Solid-state NMR measurements confirmed the successful polymerization taking place inside the nanocellulosic network, and size exclusion chromatography revealed average molecular weight (Mw) of polystyrene as approximately 700,000 Da. Moreover, the amount of the leftover monomer was found to be less than 1% as detected by gas chromatography. The dry solids content of the paste was ∼20% which is a significant increase compared to the solids content of the original CNF dispersion (1.7 wt%). The shrinkage of the CNF, MC and polystyrene structures upon drying—an often-faced challenge—was found to be acceptable for this composite containing highly hygroscopic biobased materials. At best, the two dimensional shrinkage was no more than ca. 20% which is significantly lower than the shrinkage of pure CNF being as high as 50%. The paste, which is a composite of biobased materials and a synthetic polymer, was demonstrated in direct-ink-writing to print small objects. With further optimization of the formulation, we find the emulsion templating approach as a promising route to prepare composite materials.

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