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 NIH 3T3 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.

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).