The traditional approach toward improving the crystallization rate as well as the mechanical and barrier properties of poly(lactic acid) (PLA) is the incorporation of nanocelluloses (NCs). ...Unfortunately, little study has been focused on the influence of the differences in NC morphology and dimensions on the PLA property enhancement. Here, by HCOOH/HCl hydrolysis of lyocell fibers, microcrystalline cellulose (MCC), and ginger fibers, we unveil the preparation of cellulose nanospheres (CNS), rod-like cellulose nanocrystals (CNC), and cellulose nanofibers (CNF) with different aspect ratios, respectively. All the NC surfaces were chemically modified by Fischer esterification with hydrophobic formate groups to improve the NC dispersion in the PLA matrix. This study systematically compared CNS, CNC, and CNF as reinforcing agents to induce different kinds of heterogeneous nucleation and reinforce the effects on the properties of PLA. The incorporation of three NCs can greatly improve the PLA crystallization ability, thermal stability, and mechanical strength of nanocomposites. At the same NC loading level, the PLA/CNS showed the highest crystallinity (19.8 ± 0.4%) with a smaller spherulite size (33 ± 1.5 μm), indicating that CNS, with its high specific surface area, can induce a stronger heterogeneous nucleation effect on the PLA crystallization than CNC or CNF. Instead, compared to PLA, the PLA/CNF nanocomposites gave the largest Young’s modulus increase of 350 %, due to the larger aspect ratio/rigidity of CNF and their interlocking or percolation network caused by filler–matrix interfacial bonds. Furthermore, taking these factors of hydrogen bonding interaction, increased crystallinity, and interfacial tortuosity into account, the PLA/CNC nanocomposite films showed the best barrier property against water vapor and lowest migration levels in two liquid food simulates (well below 60 mg kg–1 for required overall migration in packaging) than CNS- and CNF-based films. This comparative study was very beneficial for selecting reasonable nanocelluloses as nucleation/reinforcing agents in robust-barrier packaging biomaterials with outstanding mechanical and thermal performance.
Abstract
Structurally tunable electronic skin (e‐skin) is beneficial for advancing wearable electronics, prosthetics, and human‐machine interaction (HMI). However, the regulation of e‐skin by ...traditional nanostructure technology is complex and expensive, moreover, the nanostructure's poor deformability leads to small detection range and low sensitivity. Herein, inspired by the structure of skin‐hair and insect burr, a polypyrrole‐silk/glycerol plasticized silk fibroin (P‐silk/RG) e‐skin fabricated by a simple 3D biomimetic structural strategy is reported. Benefitting from the editability (length, position) of this structure, P‐silk/RG has a signal selectivity, long‐cilia P‐silk/RG demonstrates high sensitivity (respond to weak signal‐airflow), while the short‐cilia P‐silk/RG exhibits wide pressure detection range (0.5–200 g) and high cycle stability (8000 compressions). Therefore, different forms of P‐silk/RG are used in different scenarios (long‐cilia for monitoring breathing and coughing for motion detection and disease diagnosis, short‐cilia for pressure‐sensitive Morse code). Besides, P‐silk/RG exhibits good waterproof, editable conductive points and easy device integration, providing the basis for underwater information transmission, multibit coded command output, and early warning for emergency sports accidents and sedentary. Surprisingly, combining this structure with textile weaving can be mass‐produced. Obviously, this 3D biomimetic structure strategy endows e‐skin with editability and improved scene adaptability to provide a favorable way for mass production.
Cellulose dissolution is a worldwide issue in the production industry. Especially, the development of highly efficient and green cellulose solvents has been considered as a key factor to restrict the ...broad application of different cellulose industries. In this study, different chloride salts, such as LiCl, ZnCl2, CaCl2, and FeCl3, with different water amounts were used as green solvents to investigate the driving force of cellulose dissolution. The superfast and highly efficient cellulose dissolution in ZnCl2·3H2O and FeCl3·6H2O was successfully achieved within 5–20 min, which was confirmed by the results of polarized light microscopy. Moreover, the effect of pH and water amounts of the chloride salts on the cellulose structural change and dissolution ability was investigated for a better understanding of the role of chloride salts during the cellulose dissolution process. Especially, the dissolution mechanism of cellulose in ZnCl2·3H2O and FeCl3·6H2O has been provided compared to other non-derivatizing cellulose solvents.
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•Functionalized cellulose nanocrystals (CNCs) for dye absorption.•Selective binding of methylene blue by polydopamine-CNC.•ITC analysis confirmed the types of binding interactions.
In ...this study, cellulose nanocrystals (CNCs) were evaluated as potential adsorbents for the selective adsorption and separation of organic dyes mixtures (methylene blue (MB), with either methyl orange (MO) or rhodamine b (RB) or crystal violet (CV)). The role of surface functional groups on the dye-CNC interaction was examined using pristine and surface-functionalized CNCs, such polydopamine (PD) and melamine–formaldehyde (MF) coated CNCs (PD-CNCs and MF-CNCs respectively). Batch adsorption studies on MB/MO dye mixture showed that pristine CNCs bearing anionic sulfate ester groups exhibited preferential adsorption for MB, with a 85.78% adsorption efficiency. This preferential adsorption was further enhanced in the case of PD-CNCs, which showed 100% adsorption efficiency for MB. Additional studies on MB/RB and MB/CV dye mixtures confirmed that the improved selectivity of PD-CNCs towards MB is associated with the synergistic binding interactions, such as electrostatic attraction, π-π stacking, and hydrogen bonding. MF-CNCs with cationic amine groups displayed selective binding towards MO, an anionic dye. Also, PD-CNCs and MF-CNCs were found to completely separate MB and MO from a diluted MB/MO dye mixture. Isothermal titration calorimetry and dye flocculation experiments confirmed that the selective binding is associated with the surface-functionality of CNCs.
Textile manufacturing industries produce large amounts of viscose fiber wastes (VFW), causing serious environmental pollution. This study presents an acid-free approach to prepare spherical cellulose ...nanocrystals (SCNs) with carboxyl groups from industrial VFW by one-step hydrothermal ammonium persulfate (APS) oxidation. Novel double-response surface methodology was employed to optimize the reaction conditions. A maximum yield (37.89%) of carboxylated SCN was obtained at reaction time of 4 h, APS concentration of 1 M and temperature of 80 °C, while the SCNs showed gradual size reductions along with increase of carboxyl contents as reaction time and APS concentration increased. Interestingly, it was possible to obtain carboxylated SCNs in only 2 h of reaction with an increase of 16.5% in the crystallinity index, which was attributed to efficient swelling of cellulose chains and oxidation interaction of surface groups under hydrothermal condition. Compared with SCN-2 h, the crystallinity index and maximum degradation temperature of SCN-10 h were improved by 5.5% and 17.9 °C, respectively. Moreover, SCN-10 h exhibited excellent emulsifying capacity to stabilize soybean oil/water Pickering emulsion droplets and emulsion volume were increased with decreased mean diameter of emulsion droplets as SCN-10 h concentration increased. These results indicate that VFW is an attractive source to produce carboxylated SCNs by APS oxidation, making SCN extraction as value-added alternatives to recycle this waste. Such carboxylated SCNs have great potentials as green food Pickering emulsion stabilizers and nanofillers in high-performance composites.
In this study, conductive cellulose nanocrystals (CNCs) were coated with polypyrrole (PPy) using in situ chemical polymerization to form CNC-PPy conductive nano-network. The one-pot polymerization of ...“hard” segment methyl methacrylate (MMA) was continued onto above functionalized CNCs, then blended with “soft” molecular segment polyvinyl alcohol (PVA) to contain self-healing and conductive composite film (CPMV) fabricated by soft-hard network. In addition, the tensile strength of CPMV films with 2 wt% CNC-PPy was enhanced by 47.1%. Also, CPMV films exhibited self-healing properties due to the presence of hydrogen bonding dynamic network and showed sensitive resistance changes under external stimuli, which could be used to monitor various actions of the human body. Thus, the CPMV films present potential applications in electronic devices such as flexible electrodes, biosensors, and implantable devices.
•Cellulose nanocrystals coated with polypyrrole gave conductivity performance.•Functionalized CNCs with hard MMA chains reinforced the soft PVA composites films.•Soft-hard network contributed to robust mechanical strength of the composites.•PVA composites films showed excellent self-healing and sensing performances.
•A novel eco-friendly cellulose-based flame retardancy is prepared by modifying cellulose nanocrystal with tannic acid and phytic acid coatings.•The flame retardancy displays high thermal stability, ...expansibility, and carbonization efficiency.•The dense and continuous intumescent char layer contributes to the excellent flame-retardant performance.•The flame retardancy could be regarded as an ideal reinforcing nanofiller candidate for developing multifunctional polymers.
Cellulose nanocrystals (CNCs) with flame-retardant property attract considerable attention as multifunctional reinforcing nanofillers for the polymers. Herein, a novel eco-friendly CNC-based (CTP) flame retardancy (FR) had been developed by modifying CNC with tannic acid (TA) and phytic acid (PA). The CTP with spherical morphology displayed good thermal stability and high char residue up to 59.3 % at 600 °C. Notably, the CTP can be carbonized rapidly to form the dense and continuous intumescent char layer, which height increased from 2 mm to 16 mm. The quick dehydration and carbonization of TA under the catalysis of PA contributed to the high expansibility and carbonization efficiency of CTP. The formation of intumescent char layer acted as a strong barrier, significantly improving the flame retardancy and inhibiting the dense smoke release. This eco-friendly and high flame-retardant CNC-based FRs can be widely used for developing multifunctional polymers.
Cellulose is the most abundant renewable natural polymer on earth, but it does not conduct electricity, which limits its application expansion. The existing methods of making cellulose conductive are ...combined with another conductive material or high-temperature/high-pressure carbonization of the cellulose itself, while in the traditional method of sulfuric acid hydrolysis to extract nanocellulose, it is usually believed that a too high temperature will destroy cellulose and lead to experimental failure. Now, based on a new research perspective, by controlling the continuous reaction process and isolating oxygen, we directly extracted intrinsically conductive cellulose nanofiber (CNF) from biomass, where the confined range molecular chains of CNF were converted to highly graphitized carbon at only 90 °C and atmospheric pressure, while large-scale twisted graphene films can be synthesized bottom-up from CNFene suspensions, called CNFene (cellulose nanofiber–graphene). The conductivity of the best CNFene can be as high as 1.099 S/cm, and the generality of this synthetic route has been verified from multiple biomass cellulose sources. By comparing the conventional high-pressure hydrothermal and high-temperature pyrolysis methods, this study avoided the dangerous high-pressure environment and saved 86.16% in energy. These findings break through the conventional notion that nanocellulose cannot conduct electricity by itself and are expected to extend the application potential of pure nanocellulose to energy storage, catalysis, and sensing.
G9a, a H3K9 methyltransferase, shows elevated expression in many types of human cancers, particularly breast cancer. However, the tumorigenic mechanism of G9a is still far from clear. Here we report ...that G9a exerts its oncogenic function in breast cancer by repressing hephaestin and destruction cellular iron homeostasis. In the case of pharmacological inhibition or short hairpin RNA interference-mediated suppression of G9a, the expression and activity of hephaestin increases, leading to the observed decrease of intracellular labile iron content and the disturbance of breast cancer cell growth in vitro and in vivo. We also provide evidence that G9a interacts with HDAC1 and YY1 to form a multi-molecular complex that contributes to hephaestin silencing. Furthermore, high G9a expression and low hephaestin expression correlate with poor survival of breast cancer are investigated. All these suggest a G9a-dependent epigenetic program in the control of iron homeostasis and tumor growth in breast cancer.G9a is a histone methyltransferase highly expressed in several cancers including breast cancer. Here the authors propose a mechanism through which G9a promotes breast cancer by regulating iron metabolism through the repression of ferroxidase hephaestin.
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•Textile sensor possessed high sensitivity (GF = 8.96) and remarkable dynamic durability (5000 cycles).•The sensor showed robust mechanical performances and outstanding conductivity ...(1264 mS/m).•The textile sensor exhibited ultrasensitive response in temperature (1.53 %/°C) and full-range pH.•The sensor monitored the real-time human movement both large finger bending and subtle swallowing.•Three-dimensional conductive networks were constructed via ultrasonic-coating technology.
Flexible wearable devices with highly sensitive properties have raised enormous attention in human healthcare monitoring, soft robots and smart textiles. However, the current most researches only focus on the improvement of sensing sensitivity and the acquisition of mechanical performance, regularly ignoring the significance of wearing comfort and breathability. Herein, to overcome this challenge, we developed a fibrous sensor with three-dimensional reversible conductive networks for multiple signals monitoring via novel ultrasonic-coating technology. As a strain sensor, it possessed higher sensitivity (Gauge factor = 8.96) with excellent dynamic durability (5000 cycles) and mechanical performances than other conductive gel and film based sensors, which can meet the requirement of signal detection in various extreme environments. More surprisingly, the wearable textile sensors were assembled successfully by traditional sewing technology with different shapes. These textile sensors possessed outstanding real-time signal capture capability with temperature and full-range pH at various states such as stretching and twisting. Additionally, the textile sensors can detect different degrees of human movements such as large deformation finger bending and weak deformation swallowing, which paved the way for the development of flexible wearable devices.
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