Sixteen polymorphic primers screened from 100 random primers were selected to analyze the randomly amplified polymorphic DNA (RAPD) of 540 domesticated black goats (Capra hircas) from 9 different geographical populations in Sichuan Province of China. After the test, 170 entirely repeatable RAPD markers representing goat polymorphisms were obtained from the 16 polymorphic primers, the lengths of the markers ranging from 0.1 to 2.5 kb. The genetic distance among the black goat populations ranges from 0.1051 to 0.2978. The similarity coefficient (0.9002) between Jintang and Lezhi black goats was the highest in the 9 populations, followed by the coefficient (0.8953) between Jialing and Yinshan goats, while that between Jiangan and Huili goats was found to be the lowest (0.7424). The coefficient of differentiation among population genes (Gst) was 0.2766, indicating a comparatively low degree of differentiation among the black goat populations. A UPGMA dendrogram constructed from similarity coefficients showed that the two populations from Huili and Baiyu, which are found mostly on the Western Sichuan plateau and in mountainous areas, clustered together, and the other seven populations formed another group. It can also be clearly seen that the Huili and Baiyu populations are very special, and must have been closely related in the past, even though their link with the other populations is quite weak as a result of genetic communication. The results of the experiment offer some crucial scientific data useful for the breeding of black goats.

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Covalent adaptable networks (CANs) combine the uniqueness of thermoplastics and thermosets to allow for reprocessability while being covalently crosslinked. However, it is highly desirable but rarely achieved for CANs to simultaneously demonstrate reversibility and mechanical robustness. Herein, we report a feasible strategy to develop a novel epoxy vitrimer (EV) composed of adaptable phosphate networks (APNs), by which the EVs exhibit promising mechanical properties (tensile strength of 62.5 ~ 87.8 MPa and tensile modulus of 1360.1 ~ 2975.3 MPa) under ambient conditions. At elevated temperatures, the topology rearrangement occurs relied on phosphate transesterification, which contributes to the shape memory performance, self-healing, reprocessing, and welding behaviors. Moreover, the incorporation of APNs allows for improvements in anti-ignition and also the inhibition of both heat release and smoke generation to avoid empyrosis, asphyxiation, and toxication during burning, showing expected intrinsic fire safety. Thermal, mechanical properties, and flame retardancy of the reprocessed EVs after hot pressing are very close to those of the original EVs, which is attributed to the sufficient reversibility of APNs. Accordingly, combining the aforementioned features, EVs are manufactured as flame-triggered switches for fire alarms, which symbolizes the innovative development of high-performance covalent adaptable polymeric materials.

Dynamic covalent chemistry offers a solution to tackle the recycling issue of epoxy resins (EPs) and their carbon fiber‐reinforced composites; however, the vulnerability to creep associated with the inflammable nature of the EPs are the key obstacles for their applications. Herein, we propose a feasible and facile strategy to overcome these obstacles by incorporating phosphorus‐influenced Diels‐Alder (DA) chemistry to construct dynamic epoxy networks. In the strategy, the electron‐withdrawing phosphonate in the dienophile maleimide greatly promotes the thermal stability of the DA reaction, exhibiting excellent creep resistance, repairability, and malleability; while its flame‐retardant activity improves the fire safety of the resultant thermosets. Meanwhile, nondestructive recycling of carbon fiber is achieved. The ease with which EP and its composites can be manufactured, used, recycled and re‐used–without losing service performance–points to new orientation in sustainable composites.image

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Phosphonate, as an effective flame‐retardant group, has a dynamic phosphonate exchange behavior similar to the transesterification of carboxylate; and introducing it into the network of epoxy resin (EP) is beneficial for solving the fire risk and waste disposal problems of EP in the meantime. Herein, a reprocessable and flame‐retardant epoxy vitrimer (EV) with dual dynamic covalent reactions of phosphonate and carboxylate transesterifications is constructed by introducing a phosphonate‐containing diol named GHPP into an epoxy‐anhydride curing system. The presence of the phosphonate makes the EV intrinsically flame‐retardant; meanwhile, both of the dynamic phosphonate and carboxylate transesterifications are accelerated by the abundant primary hydroxyl groups, which show much higher activity than the as‐generated β‐hydroxyls during curing, leading to enhanced dynamic properties of the EV. As a result, on the one hand, the EV achieves the UL‐94 V‐0 rating with a high limiting oxygen index value of 37.3%; and it shows a 41% reduction for the peak heat release rate and a 39% reduction for the total heat release in the cone calorimetry test. On the other hand, such EV exhibits rapid stress relaxation and is reprocessed easily to maintain its mechanical properties, thermal properties and flame retardancy to the hilt.

2D@0D multidimensional nanoparticles (WC@TDP) were first prepared by decorating WS 2 2D nanosheets (WC) with titanium diphenylphosphonate (TDP) 0D nanoparticles, which were derived from the hybridization of diphenylphosphinic acid and TiO 2 . The chemical structure and micromorphology of the modified 2D nanosheet were confirmed, and TDP nanoparticles were tightly attached to the exfoliated WC nanosheets through noncovalent interactions. Afterward, WC@TDP was incorporated into the epoxy resin (EP), showing the improved dispersion and distribution in the thermosetting matrix. Because TDP exhibits catalytic charring activity and WC acts as a physical barrier, such EP/ WC@TDP nanocomposites exhibited the enhanced fire safety, including flame retardation and smoke suppression during burning. The composite containing 8 wt % WC@TDP passed UL94 V-0 rating with a limiting oxygen index increased from 26.0 to 34.0 vol %. Compared with those of neat EP, the peak heat release rate, total heat release rate, and total smoke release of EP/8WC@TDP were reduced by 42%, 17%, and 38%, respectively, without sacrificing the mechanical properties of the nanocomposites.

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