Synthesis of textured polysaccharide-silica nanocomposites: comparison between cellulose and chitin nanorods' precursors

International audienceThe properties and formation mechanisms of silica-based nanocomposites textured by polysaccharidenanorods have been studied from a series of new materials obtained using cellulose nanocrystals(CNCs), and their comparison with those obtained using equivalent chitin nanorods. Stable ethanolicco-suspensions of CNCs and siloxane oligomers have been processed by spray-drying to form hybridcellulose–silica nanocomposites. The materials’ surface and internal texture, before and after calcination,are highly informative about the distribution and templating role of the polysaccharide nanorods (celluloseor chitin). Both electron microscopy and nitrogen sorption analyses highlight the role of the particledimensions in defining the porosity of calcined silica replicas. In addition, the structures of the polysaccharidecrystals inside the nanocomposites were investigated by XRD and 13C solid-state NMR. From these results, it isconcluded that both polysaccharide crystalline precursors form the same sort of silica-based nanocomposites,with no visible effect of their different surface chemistry towards templating. There are strong interactionsbetween the polysaccharide surface and the siloxane oligomers that can be explained by the high density ofhydroxyl groups on the sugar cycles. During the sol–gel processing, these interactions favour the formationof a silica shell around the nanocrystals accompanied by a slight contraction of the cellulose and chitincrystal structures, not observed until now. When the spray-dried nanocomposites are subjected toammonia vapours, the siloxane condensation increases and, concomitantly, the role of the interactions atthe siloxane–polysaccharide interface is decreased. This study leads therefore to new insights and opportunitiesfor the design of nanocomposites or porous materials, the properties of which can be tuned by the choice ofpolysaccharide nanorods with specific dimensions and functionalities