Multi-scale model for the hierarchical architecture of native cellulose hydrogels

• Partially deuterated cellulose hydrogels have been synthesized.
• The hierarchical assembly has been characterised using a multi-technique approach.
• A multi-phase core-shell model has been constructed.
• Water plays an essential role on the multi-scale structure of cellulose hydrogels.
• Protiated and deuterated hydrogels present an analogous architecture.

The structure of protiated and deuterated cellulose hydrogels has been investigated using a multi-technique approach combining small-angle scattering with diffraction, spectroscopy and microscopy. A model for the multi-scale structure of native cellulose hydrogels is proposed which highlights the essential role of water at different structural levels characterised by: (i) the existence of cellulose microfibrils containing an impermeable crystalline core surrounded by a partially hydrated paracrystalline shell, (ii) the creation of a strong network of cellulose microfibrils held together by hydrogen bonding to form cellulose ribbons and (iii) the differential behaviour of tightly bound water held within the ribbons compared to bulk solvent. Deuterium labelling provides an effective platform on which to further investigate the role of different plant cell wall polysaccharides in cellulose composite formation through the production of selectively deuterated cellulose composite hydrogels.