Interest in nanofibrillated cellulose (NFC) has increased notably over recent decades. This bio-based nanomaterial has been used essentially in bionanocomposites or in paper thanks to its high mechanical reinforcement ability or barrier property respectively. Its nano-scale dimensions and its capacity to form a strong entangled nanoporous network have encouraged the emergence of new high-value applications. It is worth noting that chemical surface modification of this material can be a key factor to achieve a better compatibility with matrices. In order to increase the compatibility in different matrices or to add new functions, surface chemical modification of NFC appears to be the prior choice to conserve its intrinsic nanofibre properties. In this review, the authors have proposed for the first time an overview of all chemical grafting strategies used to date on nanofibrillated cellulose with focus on surface modification such as physical adsorption, molecular grafting or polymer grafting.

The present study reports for the first time a method to obtain water redispersible dried NFC using freeze-drying. No chemical surface modification was required to get this kind of product. Salt addition (sodium chloride: NaCl) strategy has been selected to block and then to regenerate hydrogen bonds during the drying and the redispersion steps, respectively. Several samples were produced at different pH (i.e., 4, 6, 8, and 10). All the redispersed NFC were characterized by different techniques (e.g., FE-SEM, XRD, EPMA-EDX) to check the effect of salt on NFC aggregation. The interactions between NFC and NaCl at different pH conditions have been discussed and the rheology of the redispersed NFC suspension has been performed. All the results prove a perfect water redispersion at pH 8 and exactly similar suspension is obtained after water dispersion of dried NFC following our procedure. These results are very promising for increasing application of NFC.

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