Programmable Birefringent Patterns from Modulating the Localized Orientation of Cellulose Nanocrystals

Soft and tough cellulose nanocrystals interlocked with polyacrylate-bearing cyanobiphenyl ionogels through a double network strategy

There are several examples of double network gels prepared from cellulose nanocrystals (CNC) conjugated with water-soluble polymers. However, soft but tough gels composed of mostly CNCs have been challenging to design due to aggregation or precipitation of CNCs at higher concentrations in solvated and gelled systems. We report a general strategy to introduce covalent and non-covalent interactions within cellulose nanocrystals (CNCs) to develop tough, processable, liquid crystalline (LC) gels. A liquid crystalline 12-methylene spacer cyanobiphenyl (CB12OH), is grafted onto acrylic acid via Steglich esterification and subsequently copolymerized with acrylic acid via free radical polymerization to afford an amphiphilic liquid crystalline polymer (LCP), PAACB12-r-PAA. The free carboxyl (COOH) groups from polyacrylic acid (PAA) in the copolymer are randomly interlocked with the hydroxyl (OH) groups of CNC through covalent crosslinking and host-guest supramolecular hydrogen bonding in DMSO and 1-butyl-3-methylimidazolium acetate ionic liquid. The dominant cyanobiphenyl-cyanobiphenyl (CB12-CB12) interactions yield hierarchically structured, tough, free-standing liquid crystalline nanocomposite ionogels. Rheological studies of the interlocked free-standing ionogels display a typical crosslinked gel behavior with the storage moduli (G') ranging 103-104 Pa across the entire angular frequency range. Mechanical properties are tailored by varying the concentration of CNCs in the nanocomposite gel. This facile design provides a general strategy to prepare soft and tough liquid crystalline gels from renewable resources.

Multi-Modal Melt-Processing of Birefringent Cellulosic Materials for Eco-Friendly Anti-Counterfeiting

Ubiquitous anti-counterfeiting materials with a rapidly rising annual consumption (over 1010 m2) can pose a serious environmental burden. Biobased cellulosic materials with birefringence offer attractive sustainable alternatives, but their scalable solvent-free processing remain challenging. Here, a dynamic chemical modification strategy is proposed for multi-modal melt-processing of birefringent cellulosic materials for eco-friendly anti-counterfeiting. Relying on the thermal-activated dynamic covalent-locking of the spatial topological structure of preferred oriented cellulose, the strategy balances the contradiction between the strong confinement of long-range ordered structures and the molecular motility required for entropically-driven reconstruction. Equipped with customizable processing forms including mold-pressing, spinning, direct-ink-writing, and blade-coating, the materials exhibit a wide color gamut, self-healing efficiency (94.5%), recyclability, and biodegradability. Moreover, the diversified flexible elements facilitate scalable fabrication and compatibility with universal processing techniques, thereby enabling versatile and programmable anti-counterfeiting. The strategy is expected to provide references for multi-modal melt-processing of cellulose and promote sustainable innovation in the anti-counterfeiting industry.

Evaporation-induced self-assembly of liquid crystal biopolymers

Evaporation-induced self-assembly (EISA) is a process that has gained significant attention in recent years due to its fundamental science and potential applications in materials science and nanotechnology. This technique involves controlled drying of a solution or dispersion of materials, forming structures with specific shapes and sizes. In particular, liquid crystal (LC) biopolymers have emerged as promising candidates for EISA due to their highly ordered structures and biocompatible properties after deposition. This review provides an overview of recent progress in the EISA of LC biopolymers, including DNA, nanocellulose, viruses, and other biopolymers. The underlying self-assembly mechanisms, the effects of different processing conditions, and the potential applications of the resulting structures are discussed.

Chitin nanocrystals stabilized liquid metal for highly stretchable and anti-freeze hydrogels as flexible strain sensor

Conductive hydrogels show extensive applications in flexible electronics and biomedical areas, but it is a challenge to simultaneously achieve high mechanical properties, satisfied electrical conductivity, good biocompatibility, self-recovery and anti-freezing properties through a simple preparation method. Herein, chitin nanocrystals (ChNCs) were employed to encapsulate liquid metal nanoparticles (LMNPs) to ensure the dispersion stability of LMNPs in a hydrogel system composed of polyacrylamide (PAM) and polyvinyl alcohol (PVA). The synergistic effect of ChNCs-stabilized LMNPs imparts remarkable conductivity to the hydrogel, making it an effective strain sensor for human motion. With 1 % LMNPs, the composite hydrogel stretches up to 2100 %, showing excellent stretchability. Under 10 cycles of 200 % strain, hysteresis loop curves overlap, indicating outstanding fatigue resistance. The hydrogel exhibits remarkable self-recovery, enduring 1400 % deformation without rupture. In addition, its effective antifreeze properties result from immersion in a glycerol-water solvent. Even at -20 °C and 60 °C, the hydrogel maintains stable, reproducible resistance changes at 150 % tensile strain. Therefore, the high-performance conductive hydrogel containing ChNCs stabilized LM has promising applications in flexible wearable sensing devices.

Plasmonic metasurfaces of cellulose nanocrystal matrices with quadrants of aligned gold nanorods for photothermal anti-icing

Cellulose nanocrystals (CNCs) are intriguing as a matrix for plasmonic metasurfaces made of gold nanorods (GNRs) because of their distinctive properties, including renewability, biodegradability, non-toxicity, and low cost. Nevertheless, it is very difficult to precisely regulate the positioning and orientation of CNCs on the substrate in a consistent pattern. In this study, CNCs and GNRs, which exhibit tunable optical and anti-icing capabilities, are employed to manufacture a uniform plasmonic metasurface using a drop-casting technique. Two physical phenomena-(i) spontaneous and rapid self-dewetting and (ii) evaporation-induced self-assembly-are used to accomplish this. Additionally, we improve the CNC-GNR ink composition and determine the crucial coating parameters necessary to balance the two physical mechanisms in order to produce thin films without coffee rings. The final homogeneous CNC-GNR film has consistent annular ring patterns with plasmonic quadrant hues that are properly aligned, which enhances plasmonic photothermal effects. The CNC-GNR multi-array platform offers above-zero temperatures on a substrate that is subcooled below the freezing point. The current study presents a physicochemical approach for functional nanomaterial-based CNC control.