Abstract
Aqueous suspensions of cellulose nanocrystals (CNCs) are known to self-assemble into a chiral nematic liquid crystalline phase, leading to solid-state nanostructured colored films upon solvent evaporation, even in the presence of templating agents. The angular optical response of these structures, and therefore their visual appearance, are completely determined by the spatial arrangement of the CNCs when the drying suspension undergoes a transition from a flowing and liquid crystalline state to a kinetically arrested state. Here, it is demonstrated how the angular response of the final film allows for retrieval of key physical properties and the chemical composition of the suspension at the onset of the kinetic arrest, thus capturing a snapshot of the past. To illustrate this methodology, a dynamically evolving sol-gel coassembly process is investigated by adding various amounts of organosilica precursor, namely, 1,2-bis(trimethoxysilyl)ethane. The influence of organosilica condensation on the kinetic arrest can be tracked and thus explains the angular response of the resulting films. The a posteriori and in situ approach is general; it can be applied to a variety of additives in CNC-based films and it allows access to key rheological information of the suspension without using any dedicated rheological technique.
Highlights
Aqueous suspensions of cellulose nanocrystals (CNCs) are known to self-assemble into a chiral nematic liquid crystalline phase, leading to solid-state nanostructured colored films upon solvent evaporation, even in the presence of templating agents
We investigated a dynamically evolving sol-gel co-assembly process by various amounts of organosilica precursor addition, namely 1,2-bis(trimethoxysilyl)ethane (BTMSE)
CNC self-assembly is compatible with several sol-gel precursors such as tetramethyl orthosilicate (TMOS), tetraethyl orthosilicate (TEOS) and organosilica precursors allowing for the fabrication of mesoporous structures inheriting their characteristic chiral photonic properties.[10,11,12,13]
Summary
Aqueous suspensions of cellulose nanocrystals (CNCs) are known to self-assemble into a chiral nematic liquid crystalline phase, leading to solid-state nanostructured colored films upon solvent evaporation, even in the presence of templating agents. If the added BTMSE would not modify the twisting between CNCs, we could expect the final pitch p 0 of vertical domains to increase as a direct proportion of the added volume fraction of incorporated OS
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