A dry and fully dispersible bacterial cellulose formulation as a stabilizer for oil-in-water emulsions

Supplementary material related to this article can be found, in theonline version, at: doi:https://doi.org/10.1016/j.carbpol.2019.115657Bacterial cellulose (BC) is an emerging alternative to plant cellulose in different applications. Several works demonstrated the potential of never-dried BC; however, envisioning real industrial applications, a dry product retaining its functional properties upon rehydration is preferable. A dry and completely redispersible formulation of BC with carboxymethyl cellulose (CMC) was prepared by Spray-drying. The obtained material showed a Zeta Potential of (-67.0±3.9) mV, a Dv(50) of (601±19.7) µm and was able to decrease the oil/water interface energy. The dry BC:CMC formulation was employed as stabilizer in oil-in-water emulsions, in parallel with commercial plant celluloses and Xanthan gum. The emulsions were monitored over time by optical microscopy and characterized by rheological measurements. BC:CMC effectively stabilized emulsions against coalescence and creaming, at a concentration of 0.50 % - contrarily to other commercial dry celluloses due to the Pickering effect and to the structuring of the continuous phase, as seen with Cryo-SEM.This study was supported by the Portuguese Foundation for Scienceand Technology (FCT) under the scope of the strategic funding of UID/BIO/04469 unit, COMPETE 2020 (POCI-01-0145-FEDER-006684) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund (ERDF) under the scope of Norte2020. FCT also supported this work by funding UID/EQU/00511/2019 unit, Project POCI-01-0145-FEDER-028715 funded by FEDER funds through COMPETE 2020 and by national funds (PIDDAC) throughFCT/MCTES, and Project NORTE-01-0145-FEDER-000005, funded by ERDF under the scope of NORTE 2020. The authors also acknowledgeFCT for the PhD scholarship SFRH/BD/115917/2016 (Daniela Martins) and for the contract based on “Lei do Emprego Científico” (DL 57/2016) (Berta Estevinho).info:eu-repo/semantics/publishedVersio

Fractionation of cellulose nanocrystals : enhancing liquid crystal ordering without promoting gelation

Colloids of electrically charged nanorods can spontaneously develop a fluid yet ordered liquid crystal phase, but this ordering competes with a tendency to form a gel of percolating rods. The threshold for ordering is reduced by increasing the rod aspect ratio, but the percolation threshold is also reduced with this change; hence, prediction of the outcome is nontrivial. Here, we show that by establishing the phase behavior of suspensions of cellulose nanocrystals (CNCs) fractionated according to length, an increased aspect ratio can strongly favor liquid crystallinity without necessarily influencing gelation. Gelation is instead triggered by increasing the counterion concentration until the CNCs lose colloidal stability, triggering linear aggregation, which promotes percolation regardless of the original rod aspect ratio. Our results shine new light on the competition between liquid crystal formation and gelation in nanoparticle suspensions and provide a path for enhanced control of CNC self-organization for applications in photonic crystal paper or advanced composites