Optical Properties of Self‐Assembled Cellulose Nanocrystals Films Suspended at Planar–Symmetrical Interfaces

Abstract

Hierarchically structured materials comprising rod-like, chiral, nanoparticles are commonly encountered in nature as they can form assemblies with exceptional optical and mechanical characteristics. These include cellulose nanocrystals (CNCs), which have a large potential for the fabrication of bioinspired materials mimicking those advanced properties. Fine-tuning the optomechanical properties of assemblies obtained from CNCs hinges on the transformations from suspensions of liquid crystals to long-range order in the dry state. So far, associated transitions have been studied using trivial interfaces such as planar substrates. Such transitions are explored as they evolve onto meshed supports. The meshed substrate offers a complex topology, as is encountered in nature, for the formation of CNCs films. The CNCs self-assembly occurs under confinement and support of the framework bounding the mesh openings. This leads to coexisting suspended and supported nanoparticle layers exhibiting nematic and/or chiral nematic order. Optical microscopy combined with crossed polarizers indicate that the formation of the suspended films occurs via intermediate gelation or kinetic arrest of CNCs across the mesh's open areas. The formation of self-standing, ultrathin films of CNCs with tunable optical properties, such as selective reflections in the visible range (structural color), is demonstrated by using the presented simple and scalable approach.

Surface Modification of Cured Inorganic Foams with Cationic Cellulose Nanocrystals and Their Use as Reactive Filter Media for Anionic Dye Removal

“…Both filament and film formation are typical for CNCs. 68 , 69 It seemed that CTAB, despite being cationic, did not hinder the surface modification of the geopolymers by cationic CNCs. One possible explanation for this is the prolonged contact between CNCs and the geopolymer, which enabled the CNC particles to find the optimum location (i.e., the absence of CTAB) to attach onto.…”

Asymmetrical coffee rings from cellulose nanocrystals and prospects in art and design

“…Also, coatings made from CNCs are susceptible to swelling and structural damage when exposed to water but this is addressable by application of water-resistant coatings, as exists for traditional coloring methods. The expanded fundamental understanding of CNC self-assembly may also benefit related goals, for example the development of coatings for fabrics (Tardy et al 2017).…”

Expanding the upper limits of robustness of cellulose nanocrystal aerogels: outstanding mechanical performance and associated pore compression response of chiral-nematic architectures

“…The properties of cn-CNC materials can be altered by various processes such as topography control and the use of magnetic elds or by the incorporation of additives. [28][29][30][31] Chiral nematic arrangements of nanoparticles are omnipresent in biological systems simultaneously providing high strength and toughness as well as other properties, such as selective light reection. 32 While cn ordering occurs naturally in plants and animals, top-down processing to mimic such architectures is challenging, particularly in scales above a few mm.…”