Adsorption of biopolymers onto nanocelluloses for the fabrication of hollow microcapsules

Abstract In this work, we studied the multilayer adsorption of cellulose nanocrystals and cellulose nanofibers with other polysaccharides such as xyloglucan and chitosan. We showed that the specific interactions between these biopolymers can be exploited to prepare three-dimensional functional materials. Quartz crystal microbalance studies showed that both biopolymers were adsorbed irreversibly on the nanocellulose surfaces. In aqueous media, the maximum amount of adsorbed polymer was higher for the smaller and more crystalline cellulose nanocrystals, compared to cellulose nanofibers. For both nanocelluloses employed, the amount of xyloglucan of the first bilayer was larger than the amount of chitosan adsorbed. Ellipsometry showed that both xyloglucan and chitosan were adsorbed on nanocellulose surfaces. However, at the second layer no mass change was detected by quartz crystal microbalance when xyloglucan was added, while for addition of successive layers of chitosan a decrease of frequency was detected. The water uptake of multilayers was higher for cellulose nanocrystals than for nanofibers, which was ascribed the presence of voids in the nanocrystal layer. Finally, we demonstrated that multilayer adsorption of these biopolymers can be performed on calcium carbonate sacrificial templates, which can then be removed to yield hollow polysaccharide microcapsules.