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The microscopically structural switching of supramolecular networks endows programmable gel materials with dynamic hiding properties and functionalities. However, the reconstruction of supramolecular network will destroy the programming information imprinted on the original network structure, making it difficult to restore to the original state. Here, a novel intelligent programmable photonic gel composed of cellulose nanocrystals (CNC) and acrylamide is constructed. The mechanical properties and optical signals of gel can be switched reversibly on demand by reasonably designing the winding and compression between molecular structures. Under this conversion mechanism, the rigid "skeleton" constructed from the CNC chiral structure perfectly acts as the coding substrate. Importantly, even after multiple dynamic switching of the supramolecular network, the encoded information can be displayed completely and accurately on the CNC chiral structure in the stretched state. In addition, the 5D controllable conversion of stiffness, transparency, stretchability, color, and shape greatly improves the security and confidentiality of the encoded information inside the gel. This is a successful example of the application of CNC chiral structure in switchable supramolecular network materials. It is believed that the flexible variability and advanced camouflage give the intelligent gel the potential to be used in a wider range of practical scenarios. [ABSTRACT FROM AUTHOR]

The charge plays an important role in cellulose nanocrystal (CNC) self-assembly to form liquid crystal structures, which has rarely been systematically explored. In this work, a novel technique combining atomic force microscopy force and atomistic molecular dynamics simulations was addressed for the first time to systematically investigate the differences in the CNC self-assembly caused by external positive and negative charges at the microscopic level, wherein sodium polyacrylate (PAAS) and chitosan oligosaccharides (COS) were used as external positive and negative charge additives, respectively. The results show that although the two additives both make the color of CNC films shift blue and eventually disappear, their regulatory mechanisms are, respectively, related to the extrusion of CNC particles by PAAS and the reduction in CNC surface charge by COS. The two effects both decreased the spacing between CNC particles and further increased the cross angle of CNC stacking arrangement, which finally led to the color variations. Moreover, the disappearance of color was proved to be due to the kinetic arrest of CNC suspensions before forming chiral nematic structure with the addition of PAAS and COS. This work provides an updated theoretical basis for the detailed disclosure of the CNC self-assembly mechanism. [ABSTRACT FROM AUTHOR]

Widely employed petroleum-based food packaging materials have inflicted irreparable harm on ecosystems, primarily stemming from their non-biodegradable attributes and recycling complexities. Inspired by natural nacre with a layered aragonite platelet/nanofiber/protein multi-structure, we prepared high-barrier composite films by self-assembly of cellulose nanofibrils (CNF), cellulose nanocrystals (CNC), montmorillonite (MMT), polyvinyl alcohol (PVA) and alkyl ketene dimer (AKD). The composite films demonstrated outstanding barrier properties with oxygen vapor transmission of 0.193 g·mm·m−2·day−1 and water vapor transmission rates of 0.062 cm3·mm·m−2·day−1·0.1 MPa−1, which were significantly lower than those of most biomass-degradable packaging materials. Additionally, the impacts of mixing nanocellulose with various aspect ratios on the tensile strength and folding cycles of the films were examined. The exceptional resistance of the composite films to oil and water provides a novel and sustainable approach to reduce non-biodegradable plastic packaging. [ABSTRACT FROM AUTHOR]

The production of sustainable bioaerogel by using renewable biomass via eco‐friendly techniques is a meaningful research topic. This study reports a facile bottom‐up green strategy to construct dimensionally stable bioaerogel derived from bacterial cellulose (BC). Taking advantages of the natural hierarchical and interconnected network structure of BC, the preparation of bioaerogel comprises directional freezing, followed by freeze‐drying approach. Aside from the multifunctional characteristics such as high porosity, low density, and large specific surface area, the resultant BC bioaerogels show superhydrophilic property, excellent water absorption, and swelling characteristics. In addition, the extremely compressed bioaerogel film exhibits flexibility and good mechanical properties. And the BC bioaerogels display a low coefficient of thermal conductivity (25.8 mW m−1 K−1). Moreover, the BC bioaerogels reveal excellent sound absorption at board frequencies from 200 to 6000 Hz with a maximum sound‐absorption coefficient of 0.97. The BC bioaerogel is further used as the green, sustainable, and degradable cigarette filter tip, exhibiting good adsorption effect for the smoke main components. In summary, this study provides a feasible solution to rationally construct lightweight, high porous, heat‐insulating, and highly efficient sound‐adsorption BC bioaerogel, which has potential applications in the future as green advanced functional materials. [ABSTRACT FROM AUTHOR]

We describe an effective method to create nanocomposites of silver nanoparticles that were stabilized by cellulose nanofibrils (CNF-AgNPs) that were then mixed with a starch matrix. The incorporation of CNF-AgNPs nanocomposites significantly enhanced the mechanical and antibacterial properties of hybrid films. The starch-based films with only 5.0 wt% CNF-AgNPs content exhibited superior mechanical properties in which the Young's modulus increased from 80.3 to 381.5 MPa and tensile strength increased from 6.06 to 9.96 MPa at 50% RH. Taking advantage of the denser microstructure and strong interfibrillar networks, the nanocomposite film can resist more external tensile forces and show excellent barrier property and thermostability. Moreover, antibacterial analysis indicated that CNF-AgNPs/starch nanocomposite films exhibited strong bactericidal effects against representative both Escherichia coli and Staphylococcus aureus. The cell viability of 87.71% and clear morphologies of live cells implied good biocompatibility of nanocomposite films. The demonstrated characteristics of CNF-AgNPs/starch nanocomposite film verified its suitability as a sustainable material for food packaging. [ABSTRACT FROM AUTHOR]

Lipstick is a kind of popular cosmetic, which can give the lip a beautiful color and improve its appearance. The problem is that dye molecules would be in contact with the skin, whereas the lipstick made with dyed CNCs (CNC-lipstick) would reduce the contact. Herein, we demonstrated that the deficiency of color migration can be overcome by using the cellulose nanocrystal (CNC) dye to replace conventional dye in the lipstick substrates. The lipstick containing CNC dye (CNC-lipstick) could effectively inhibit the color migration and was easily erased as compared to ordinary lipsticks. The color change on the scoured skin was as high as ΔE* = 30.4 after using red ordinary dye-lipstick for 8 h, and red residue was clearly observed in the texture of the skin. Further cleaned with makeup remover, the color change on the scoured skin was ΔE* = 6.4. Notably, the color change of CNC-lipstick was ΔE* < 5, and only a small amount of red residue could be observed in the texture of the skin. The reduction of color migration from the lipstick to the skin was probably due to the fact that the dye absorbed by the CNC, which slowed down the diffusion rate of dye molecules. Our work paves the way for using CNC dye for inhibiting color migration in the lipstick application. Cellulose nanocrystals were applied to prepare the color easy-cleaned lipstick. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • We first investigated the hornification of nanocellulose (CNCs, CNF) during dehydration with different solid content. • In order to avoid the effect of drying, liquid AFM mode was carried out in this work. • The different water contents of nanocellulose were quantified by Differential Scanning Calorimetry (DSC). • The amount of free water, freezing bound water, and non-freezing bound water were completely removed in sequence. • The hydroxyl accessibility of both redispersed CNCs and CNF were reduced via evaluating the uptake of fluorescent dyes. Abstract Hornification are usually occurred in cellulosic fibers and even in nanocellulose fibrils during dehydration process but their mesoscopic structural changes is not fully understood. Here we investigated the structural features of cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNF) with different solid content. In order to avoid the effect of drying, liquid AFM mode was carried out in this work. The different water contents of nanocellulose were quantified by Differential Scanning Calorimetry (DSC). We showed evidence of extreme growth in radial direction in the redispersed nanocelluloses, analyzed by statistics of contours from microscopy images. The amount of free water, freezing bound water, and non-freezing bound water decreased gradually during water evaporation and were completely removed in sequence. In addition, the hydroxyl accessibility of both redispersed CNCs and CNF were reduced by 83.33% and 81.96% via evaluating the uptake of fluorescent dyes. [ABSTRACT FROM AUTHOR]

Cellulose nanocrystals (CNCs) have excellent properties, such as reproducibility, low biodegradability and a large amount of reactive hydroxyl groups on the surface. This study focused on the labeling efficiency and fluorescent properties of the fluorescent labeling of CNCs by means of electrostatic adsorption and covalent bonding. The CNCs in the sample were approximately 94.76% successfully labeled with dyes, and the number of dye molecules adsorbed by per CNC was approximately 208 by electrostatic adsorption. For the sample covalently linked, the efficiency of the fluorescent labeling was 95.51%, and the number of dye molecules attached to per CNC was 1038. The quenching mode of the fluorescent CNCs was dynamic quenching. The fluorescence lifetime and quantum yield of the fluorescent CNCs increased by 1–2 times compared to the free dye. A thorough investigation of the relation between the binding mechanism and the fluorescent properties in fluorescent CNCs was conducted. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new method is proposed to prepare the carboxylated cellulose nanocrystals. • The cellulose nanocrystals with high yield and high crystallinity are obtained. • The carboxylated cellulose nanocrystals is used as Pickering emulsion stabilizer. • The stability of emulsion is excellent under low pH or low salt concentration. • The stabilization mechanism of Pickering emulsions is systematically demonstrated. The preparation of carboxylated cellulose nanocrystals (cCNCs) and their stabilization in oil-in-water (O/W) Pickering emulsions hold great potential for application and research value. In this work, a novel integrated oxidation strategy was proposed to prepare needle-like cCNCs by sodium periodate (NaIO 4)/Fenton (SF-cCNCs) with considerable yield (58.58 %), plentiful carboxyl groups (1.28 mmol/g), and high crystallinity (83.3 %). The distinctive features of smaller size and high viscosity accelerated the as-prepared SF-cCNCs to be used in stabilizing Pickering emulsion. Moreover, the effects of oil–water ratio (OWR), SF-cCNCs content, pH, and sodium chloride (NaCl) content on the stability of SF-cCNCs-stabilized Pickering emulsions were also investigated systematically. Interestingly, the stability of the as-obtained emulsions was dependent on pH and salt. Afterwards, the rheological behaviors validated that the emulsion viscosity increased rapidly after adding NaCl, which was dominated by the elastic behavior. Finally, the main stabilization mechanism was confirmed to be interfacial adsorption of SF-cCNCs rather than the formation of spatial network structures between droplets. This study reports a synthetic strategy to efficiently prepare SF-cCNCs, endowing the SF-cCNCs stabilized Pickering emulsion with environmentally friendly, long-term stable and highly anti-agglomeration abilities for cosmetics and food products. [ABSTRACT FROM AUTHOR]

Structural color is an eye-catching phenomenon in nature, which originates from the synergistic effect of cholesteric structure inside living organisms and light. However, biomimetic design and green construction of dynamically tunable structural color materials have been a great challenge in the field of photonic manufacturing. In this work, the new ability of L-lactic acid (LLA) to multi-dimensionally modulate the cholesteric structures constructed from cellulose nanocrystals (CNC) is revealed for the first time. By studying the molecular-scale hydrogen bonding mechanism, a novel strategy that electrostatic repulsion and hydrogen bonding forces jointly drive the uniform arrangement of cholesteric structures is proposed. Due to the flexible tunability and uniform alignment of the CNC cholesteric structure, different encoded messages were developed in the CNC/LLA (CL) pattern. Under different viewing conditions, the recognition information of different digits will continue to reversibly and rapidly switch until the cholesteric structure is destroyed. In addition, the LLA molecules facilitated the more sensitive response of the CL film to the humidity environment, making it exhibit reversible and tunable structural colors under different humidity. These excellent properties provide more possibilities for the application of CL materials in the fields of multi-dimensional display, anti-counterfeiting encryption, and environmental monitoring. [ABSTRACT FROM AUTHOR]

• Efficiency was improved by more than 97 % without time-consuming dialysis. • About 16 % yield of Cellulose nanocrystals were obtained by dilute acid hydrolysis. • More than 69 % yield of cellulose nanofibers were obtained after microfluidization. • Higher thermostability was the significant advantages of cellulose nanocrystals. • The finding enhanced clean production of nanocellulose by solving waste-acid. Nanocellulose has gained increasing attention due to its excellent properties and wide application prospect. However, fast and low-waste preparation of nanocellulose is still challenging. Here, a time-saving and low-cost chemi-mechanical method was proposed to prepare cellulose nanocrystals (D-CNCs) and cellulose nanofibers (D-CNFs) by dilute sulfuric acid hydrolysis and the homogenization of the un-hydrolyzed cellulose residues, respectively. After hydrolyzed by 0.3 wt% sulfuric acid at 160 °C for 2 h, the diameter and length distribution of the obtained D-CNCs were 16 ∼ 45 nm and 150 ∼ 600 nm, respectively. The yield of D-CNCs and D-CNFs reached to 15.78 % and 69.11 %. The thermostability of D-CNCs was more superior to CNCs manufactured by 64 wt% sulfuric acid. In conclusion, this approach offers a promising strategy for high yield of nanocellulose due to its easy operation and low pollution. [ABSTRACT FROM AUTHOR]