Effect of the Crosslinking Degree on Self-Healing Poly(1,2,3-Triazolium) Adhesive.

Dynamic covalent materials are a class of polymer that could be stress-relaxation, reprocessable, and self-healing due to dynamic crosslinks in network. Dynamic crosslinks play an important role in the typical characteristic of self-healing polymers. It is meaningful to understand the effect of crosslinking degree on the properties of poly(1,2,3-triazolium) (PTAM). In this article, the dynamic covalent network of PTAM adhesive has been used to study the effect of crosslinking degree. A series of PTAM adhesive with different crosslinking degrees have been obtained by changing the amount of crosslinker. Adhesion property can first rise then fall down with the increase of crosslinking degree and the best lap-shear strength is above 20 MPa. Creep resistance and solvent resistance can be enhanced with the increase of crosslinking degree. Self-healing studies have shown that crosslinking degree can enhance the ability of self-healing, but too high crosslinking degree raises the temperature of self-healing and causes side reaction which reduces the self-healing efficiency. These results provide some insights for the influence of the crosslinking degree on the self-healing and the structural design of dynamic covalent materials.

High impact polytriazole resins for advanced composites.

Three azido-terminated poly(ethylene glycol) macromonomers (ATPEGs) were synthesized from poly(ethylene glycol)s (PEGs) and characterized. The extended polytriazole (EPTA) resins were prepared from the macromonomers, azide and alkyne monomers. Toughening effect of PEGs on polytriazole resins was analyzed by means of mechanical, thermal and electronic microscope characterization. The results show that molecular weight and content of ATPEGs have great influence on the thermal and mechanical properties of cured EPTA resins. The impact strength of cured EPTA resins increases with the increase of the amount and molecular weight of ATPEGs. The flexural strength and heat resistance of cured EPTA resins decrease with the increase of addition amount and molecular weight of ATPEGs. High impact EPTA resins were obtained.

Hard carbon micro-nano tubes derived from kapok fiber as anode materials for sodium-ion batteries and the sodium-ion storage mechanism.

Hard carbon materials are considered as the most promising anode for sodium-ion batteries (SIBs). However, the high cost and poor rate performance hinder their application in SIBs. Moreover, the controversial mechanism of Na-ion storage restricts the improvement of hard carbon anodes. Herein, hard carbon micro-nano tubes (HCMNTs) from low-cost biomass kapok fibers are prepared as a promising anode for SIBs. Benefitting from the micro-nano structure, which offers low surface area and short Na+ diffusion path, 1400HCMNT possesses a good initial Coulombic efficiency of 80%, a high reversible capacity of 290 mA h g-1, and an excellent rate capacity. Furthermore, electron paramagnetic resonance and thermogravimetric analysis were applied to investigate the Na-ion storage mechanism in the HCMNTs. Sodium is stored in the hard carbon in an ionic state in the slope region and as quasi-liquid metallic sodium clusters in the low-voltage plateau.

Occurrence of the (2R,3S)-Isomer of 2-Amino-3,4-dihydroxybutanoic Acid in the Mushroom Hypsizygus marmoreus.

Here, we report the occurrence of the (2R,3S)-isomer of 2-amino-3,4-dihydroxybutanoic acid (d-ADHB) in the fruiting body of an edible mushroom, Hypsizygus marmoreus. This is an unusual example of the accumulation of a d-amino acid whose enantiomer is not a proteinogenic amino acid. We show that d-ADHB occurs specifically in the mushroom H. marmoreus. Other edible mushrooms examined, including Pholiota microspora, Pleurotus eryngii, Mycena chlorophos, Sparassis crispa, Grifola frondosa, Pleurotus ostreatus, and Flammulina velutipes, do not contain detectable levels of d-ADHB. The concentration of d-ADHB in the fruiting body of H. marmoreus is relatively high (approximately 1.3 mg/g of fruiting body) and is comparable to the concentration of some of the most abundant free proteinogenic amino acids. Quantitative analysis of d-ADHB during fruiting body development demonstrated that the amino acid is synthesized during the fruiting body formation period. The absence of the putative precursors of d-ADHB, the (2S,3S)-isomer of ADHB and 2-oxo-tetronate, and the enzyme activities of d-ADHB racemase (2-epimerase) and transaminase suggested that d-ADHB is synthesized by a unique mechanism in this organism. Our data also suggested that the lack of or low expression of a d-ADHB degradation enzyme is a key determinant of d-ADHB accumulation in H. marmoreus.