Chemical modification of nanoscaled cellulosic building blocks: How to define the versatility?

It is a well-known fact that polymeric cellulose mols. are considered as versatile materials with respect to chem. modifications when compared to synthetic polymeric counterparts. Hydroxyl groups are readily able to undergo various derivatisation procedures both in aq. and in non-polar org. solvent environments. The identical versatility and effortless modification strategies are often claimed to apply for nanocellulosic materials as well due to the numerous and accessible hydroxyl groups located directly on the surfaces of fibrils or crystals prone to further functionalisations. In practice, nanocellulosic materials unfortunately often defy the facile chem. modification routes involving covalent binding. This presentation discusses the nanocellulose dispersion related challenges, which frequently result in severe agglomeration tendency of fibrils or crystals thus lowering the yield and degree of surface substitution of the endproducts. Simultaneously the precious nanoscaled fine structure is irreversibly lost. Furthermore, the purifn. processes for the modified nanocellulose grades are not trivial at all since nanoscaled materials prevent the conventional filtration and centrifugation procedures. These aspects are exemplified using simple chem. modification strategies based on APTES-chem. or pNIPAM grafting. Alternative modification strategy involving the direct interfacial modification of the already assembled nanocellulosic structures is proposed to overcome the aforementioned challenges.