Abstract The colloidal suspensions of aqueous cellulose nanocrystals (CNCs) are known to form liquid crystalline systems above certain critical concentrations. From an isotropic phase; tactoid formation; growth; and sedimentation have been determined as the genesis of a high-density cholesteric phase; which after drying; originates solid iridescent films. Herein; we report the coexistence of a liquid crystal upper phase and an isotropic bottom phase in CNC aqueous suspensions at isotropic-nematic phase separation for the first time. Furthermore; isotropic spindle-like domains are observed in the low-density liquid crystalline phase; and high-density liquid crystalline phases are also prepared. The CNCs isolated from the low- and high-density liquid crystalline phases are found to have similar average lengths; diameters; and surface charges. The existence of a liquid crystalline low-density phase is explained by the presence of air dissolved in the water present within the CNCs. The air dissolves out when the water solidifies into ice and remains within the CNCs. The self-adjustment of the cellulose chain conformation enables the entrapment of air within the CNCs and CNC buoyancy in aqueous suspensions. This article is protected by copyright. All rights reserved

Cellulose nano crystals (CNCs) are promising materials for energy efficient buildings related to the control of reflectivity and heat absorption/reflection of light. In this sense it is important to improve CNCs films fire retardant properties, which can be achieved by adding clays. Cellulose nanocrystals (CNCs) and nanolayers obtained from Sodium Fluorohectorite (NaFh) synthetic clay are both known to form liquid crystalline phases in aqueous suspensions. CNCs form cholesteric phases, which structure is preserved after water evaporation, while dry NaFh nanolayers aligned films collapse. In this initial work, it is shown that CNCs are compatible with NaFh clay. We demonstrate that the liquid crystalline phase of CNCs in water is not destroyed by the presence of NaFh nanolayers. The NaFh nanolayers act as planar anchoring surfaces to the cellulose nanorods and, after evaporation of the water coloured films are obtained. The precursor solutions and the photonic films were investigated by Describe several techniques.