All-Aqueous Liquid Crystal Nanocellulose Emulsions with Permeable Interfacial Assembly

Abstract

We report on the formation of water-in-water liquid crystal emulsions with permeable colloidal assemblies. Rodlike cellulose nanocrystals (CNC) spontaneously self-assemble into a helical arrangement with the coexistence of nonionic, hydrophilic polyethylene glycol (PEG) and dextran, whereas the two polymer solutions are thermodynamically incompatible. Stable water-in-water emulsions are easily prepared by mixing the respective CNC/polymer solutions, showing micrometric CNC/PEG dispersed droplets and a continuous CNC/dextran phase. With time, the resulting emulsion demixes into an upper, droplet-lean isotropic phase and a bottom, droplet-rich cholesteric phase. Owing to the osmotic pressure gradient between PEG and dextran phases, target transfer of cellulose nanoparticles occurs across the water/water interface to reassemble into a liquid crystal-in-liquid crystal emulsion with global cholesteric organization. The observed structural, optical, and temporal evolution confirm that the colloidal particles in the two immiscible phases experience short-range interactions and form long-range assemblies across the interface. ; This work was a part of the Academy of Finland's Flagship Programme under Project Nos. 318890 and 318891 (Competence Center for Materials Bioeconomy, FinnCERES). The authors also acknowledge support by the Canada Excellence Research Chair initiative, the Canada Foundation for Innovation (CFI), and the European Research Council under the European Union's Horizon 2020 research and innovation program (ERC Advanced Grant Agreement No. 788489, "BioElCell"). J.E. acknowledges the i-LINK1188 collaborative project, the AIE founding agency and the "Grupo de Nanotecnología Farmacéutica" UB-CSIC Associated Unit. Polarized CLSM imaging was performed in the LSI IMAGING facility of the Life Sciences Institute of the University of British Columbia using infrastructure funded by BC Knowledge Development Fund as well as a Strategic Investment Fund (Faculty of Medicine, University of British Columbia). ; Peer reviewed