Residual Strain and Nanostructural Effects during Drying of Nanocellulose/Clay Nanosheet Hybrids: Synchrotron X-ray Scattering Results

Cellulose nanofibrils (CNF) with2D silicate nanoplatelet reinforcementreadily form multifunctional composites by vacuum-assisted self-assemblyfrom hydrocolloidal mixtures. The final nanostructure is formed duringdrying. The crystalline nature of CNF and montmorillonite (MTM) madeit possible to use synchrotron X-ray scattering (WAXS, SAXS) to monitorstructural development during drying from water and from ethanol.Nanostructural changes in the CNF and MTM crystals were investigated.Changes in the out-of-plane orientation of CNF and MTM were determined.Residual drying strains previously predicted from theory were confirmedin both cellulose and MTM platelets due to capillary forces. The formationof tactoid platelet stacks could be followed. We propose that afterfiltration, the constituent nanoparticles in the swollen, solid gelalready have a "fixed" location, although self-assemblyand ordering processes take place during drying.