Preparation of phosphorus-doped chitosan derivative and its applications in polylactic acid: Crystallization, flame retardancy, anti-dripping and mechanical properties.

The topic of biobased flame-retardant PLA has always been of great interest. In our study, we successfully synthesized a phosphorus-containing chitosan derivative (PCS) and combined it with aluminum hypophosphate (AP) to create an effective flame-retardant PLA system. PCS acted as an enhancer, enhancing the thermal performance, crystallinity, and toughness of PLA/AP. Compared to PLA modified with 12 wt% AP achieving UL-94 V-2 level and 24.3 % of limited oxygen index, PLA containing 3 wt% PCS and 9 wt% AP achieved UL-94 V-0 level and limited oxygen index of 28 %. The system testing studies such as CCT, Raman, XPS, and TG-IR results indicated that PLA/AP/PCS exhibited a dual flame-retardant mechanism of condensed and gas phases.

Biosynthesis of positively charged bacterial cellulose hydrogel with antibacterial and anti-inflammatory function for efficient wound healing.

In bacterial cellulose (BC)-based living materials, the effective and permanent incorporation of bactericidal agents into BC remains a persistent challenge. In this study, midazole quaternary ammonium salt was grafted onto a dispersion of bacterial cellulose, which was subsequently directly added to the fermentation medium of BC-producing bacteria to obtain BC-based hydrogel materials (BC/BC-[PQVI]Br) with inherent antibacterial properties. The BC/BC-[PQVI]Br hydrogel prepared in this study exhibits favorable tensile properties, with a maximum tensile stress of 970 KPa and water retention for up to 6 h. Moreover, it demonstrates acceptable antibacterial activity against S. aureus (93 %) and E. coli (71 %), respectively. Additionally, the hydrogel displays a high cell survival rate of 98 % after contact with NIH3T3 cells, indicating its non-cytotoxic nature. Furthermore, the mouse wound experiment confirms the excellent wound healing effect of the hydrogel. This research presents an innovative approach towards developing environmentally friendly active wound dressings with microbial-derived antibacterial functionality.

Tensile Strength Statistics and Fracture Mechanism of Ultrahigh Molecular Weight Polyethylene Fibers: On the Weibull Distribution.

To study the distribution of ultrahigh molecular weight polyethylene fiber (UHMWPE) strength, three groups of UHMWPE fibers were spun by the gel spinning method, which was undrafted raw fibers (with high strain at break) and fibers with different prespinning and postspinning draw ratios. It is found that even when the strain at break (εb) > 46%, the tensile strength of the fiber still obeys the Weibull distribution. The draw ratio has a great influence on the distribution of fiber strength, especially the draw ratios of the spinneret in the prespinning process. It may be that different drafting processes affect the fracture mechanism of the fibers. This paper analyzes and discusses that and proves it by differential scanning calorimetry and the taut tie molecules (TTMs) fractions. The parameters of the Weibull distribution suggest the quality of the fiber. The Weibull modulus is closely related to the dispersion of the fiber properties and processing parameters. The characteristic strength is similar to the test average strength, which is more suitable for the judgment of fiber reliability in actual use. At the same time, the normality of the samples was tested by Kolmogorov-Smirnov, Shapiro-Wilk, Jarque-Bera test, and quantile-quantile (Q-Q) plots, and the strength distribution was visually displayed by the bell curve. The results show that the Gaussian distribution is not so suitable to describe the strength distribution of the stretched fiber compared to the Weibull distribution.

Hydrophobic modification of cellulose nanofibers by gallic acid and the application in pressure sensing.

Via rational molecular structure design and using gallic acid (GA) for hydrophobic modification of cellulose nanofibers (CNF), the "polymer dipole" CNF-GA with hydrophilic main chains and hydrophobic side chains was prepared, which improved the poor piezoelectric properties of CNF used for preparing pressure sensors. Due to the appearance of the side chains, the elongation at break of the CNF-GA-2, compared with CNF, was enhanced by 186 %, and the excellent tensile strength, puncture load, and tearing strength were displayed. Moreover, the significant glass transition temperature (Tg) near the human body temperature was exhibited for CNF-GA, making it possible to be applied in temperature sensing. Most importantly, the CNF-GA-2 showed the maximum hydrophobicity, with a contact angle of 76.77°. Finally, the CNF-GA-2/MXene nanocomposite film was prepared by the CNF-GA-2 with MXene through vacuum filtration. The results indicated that the film had excellent piezoelectric properties (d33 = 63.283), the generated stable induced voltage (125.6 mV), the preferable piezoresistive performance (ΔR/R0 = 2.15), the fast response/recovery time (48/61 ms), which could achieve dynamic and static responses. Moreover, this film could be used for real-time detection of limb movements (such as wrists).

Constructing a 3D Ion Transport Channel-Based CNF Composite Film with an Intercalated Structure for Superior Performance Flexible Supercapacitors.

The weak stiffness, huge thickness, and low specific capacitance of commonly utilized flexible supercapacitors hinder their great electrochemical performance. Learning from a biomimetic interface strategy, we design flexible film electrodes based on functional intercalated structures with excellent electrochemical properties and mechanical flexibility. A composite film with high strength and flexibility is created using graphene (reduced graphene oxide (rGO)) as the plane layer, layered double metal hydroxide (LDH) as the support layer, and cellulose nanofiber (CNF) as the connection agent and flexible agent. The interlayer height can be adjusted by the ion concentration. The highly interconnected network enables excellent electron and ion transport channels, facilitating rapid ion diffusion and redox reactions. Moreover, the high flexibility and mechanical properties of the film achieve multiple folding and bending. The CNF-rGO-NiCoLDH film electrode exhibits high capacitance performance (3620.5 mF cm-2 at 2 mA cm-2), excellent mechanical properties, and high flexibility. Notably, flexible all-solid assembled CNF-rGO-NiCoLDH//rGO has an extremely high area energy density of 53.5 mWh cm-2 at a power density of 1071.2 mW cm-2, along with cycling stability of 89.8% retention after 10 000 charge-discharge cycles. This work provides a perspective for designing high-performance energy storage materials for flexible electronics and wearable devices.