Caroline E P Silva1, Kam C Tam2, Juliana S Bernardes3, Watson Loh4. 1. Institute of Chemistry, University of Campinas (Unicamp), CP 6154, 13083-970 Campinas, SP Brazil; Brazilian Nanotechnology National Laboratory (LNNano), CNPEM, 13083-970 Campinas, Brazil. 2. Department of Chemical Engineering, University of Waterloo, N2L3G1 Waterloo, Canada. 3. Brazilian Nanotechnology National Laboratory (LNNano), CNPEM, 13083-970 Campinas, Brazil; Center for Natural and Human Sciences, Federal University of ABC, Santo André, São Paulo 09210-580, Brazil. Electronic address: juliana.bernardes@lnnano.cnpem.br. 4. Institute of Chemistry, University of Campinas (Unicamp), CP 6154, 13083-970 Campinas, SP Brazil. Electronic address: wloh@iqm.unicamp.br.
Abstract
HYPOTHESIS: Hydrophobic oleic acid/water interfaces are negatively charged. Hence, the use of cationic nanocelluloses as stabilizers of Pickering emulsions could improve the colloidal stability due to the electrostatic complexation at the oil-water interface. EXPERIMENTS: Two cationic nanofibrillated cellulose (cNFCs) with two degrees of substitution were prepared and used as stabilizers of Pickering emulsions. The adsorption of cNFCs at the oil: water interface was evaluated by interfacial tension, atomic force microscopy, and centrifugation measurements. LUMiSizer and optical microscopy techniques were used to analyze the colloidal stability and oil droplets morphology, respectively. Besides, the rheological behavior of the continuous aqueous phase was determined through flow and stress sweep curves. Finally, the dispersion of cNFCs in a diluted emulsion was visualized by cryogenic transmission electron microscopy (cryo-TEM). FINDINGS: Cationic NFCs were more efficient in partitioning to the oil:water interface compared to their anionic analogous, oCNF. The electrostatic attraction between the positively charged trimethylammonium groups and the negatively charged deprotonated oleic acid reduced the interfacial tension and improved the colloidal stability of O/W Pickering emulsions. cNFCs dispersed in the aqueous phase were found to increase the viscosity, decelerating the oil drops coalescence. Therefore, the stabilization of cNFCs Pickering emulsions had a synergistic effect from the electrostatic complexation at the liquid-liquid interface and network formation in the aqueous phase, as visualized by cryo-TEM.
HYPOTHESIS: Hydrophobic oleic acid/water interfaces are negatively charged. Hence, the use of cationic nanocelluloses as stabilizers of Pickering emulsions could improve the colloidal stability due to the electrostatic complexation at the oil-water interface. EXPERIMENTS: Two cationic nanofibrillated cellulose (cNFCs) with two degrees of substitution were prepared and used as stabilizers of Pickering emulsions. The adsorption of cNFCs at the oil: water interface was evaluated by interfacial tension, atomic force microscopy, and centrifugation measurements. LUMiSizer and optical microscopy techniques were used to analyze the colloidal stability and oil droplets morphology, respectively. Besides, the rheological behavior of the continuous aqueous phase was determined through flow and stress sweep curves. Finally, the dispersion of cNFCs in a diluted emulsion was visualized by cryogenic transmission electron microscopy (cryo-TEM). FINDINGS: Cationic NFCs were more efficient in partitioning to the oil:water interface compared to their anionic analogous, oCNF. The electrostatic attraction between the positively charged trimethylammonium groups and the negatively charged deprotonated oleic acid reduced the interfacial tension and improved the colloidal stability of O/W Pickering emulsions. cNFCs dispersed in the aqueous phase were found to increase the viscosity, decelerating the oil drops coalescence. Therefore, the stabilization of cNFCs Pickering emulsions had a synergistic effect from the electrostatic complexation at the liquid-liquid interface and network formation in the aqueous phase, as visualized by cryo-TEM.
Authors: Blaise L Tardy; Bruno D Mattos; Caio G Otoni; Marco Beaumont; Johanna Majoinen; Tero Kämäräinen; Orlando J Rojas Journal: Chem Rev Date: 2021-08-20 Impact factor: 72.087
Authors: André Luiz Missio; Caio G Otoni; Bin Zhao; Marco Beaumont; Alexey Khakalo; Tero Kämäräinen; Silvia H F Silva; Bruno D Mattos; Orlando J Rojas Journal: ACS Sustain Chem Eng Date: 2022-07-25 Impact factor: 9.224