A high-performance epoxy vitrimer was facilely prepared from a renewable lignin derivative vanillin, and its carbon-fiber composites were nondestructively recycled.

Epoxy thermosets containing a two-benzene-ring-conjugated Schiff base structure combined excellent controlled degradability, stability, antibacterial properties, and thermal and mechanical properties.

Vitrimers undergoing dynamic bond exchange enable reprocessing and recycle of thermosets. However, vitrimers are susceptible to creep, leading to their poor dimensional stability, which limits their applications. Here, a facile method via integration of metal complexes was utilized to address this issue, and cross-linked polyimine was selected as an example of vitrimer. Three different metal complexes were introduced into a polyimine vitrimer via a one-pot preparation involving the formation of metal complexes and cross-linking of polyimine. The addition of 0.5 mol % Cu2+ relative to imine bond reduced creep degree from 30% to 20% at 60 °C, and the creep resistance was enhanced with increasing Cu2+ content. Loading 5 mol % Cu2+ increased the initial creep temperature from 60 to about 100 °C and raised the Arrhenius activation energy (E a) for stress relaxation from 52.3 to 67.7 kJ mol–1. The ability of different metal complexes to suppress creep followed the order of Fe3+ > Cu2+ > Mg2+, and the initial creep temperature reached around 120 °C for vitrimer with 5 mol % of Fe3+. Meanwhile, the polyimine–metal complex vitrimers still exhibited excellent reprocessing recyclability. Moreover, the introduction of coordination structures enhanced the thermal and mechanical properties, solvent, and acid resistance. Thus, metal coordination is an efficient approach to achieve high-temperature creep resistance, excellent thermal and mechanical properties, and chemical stability for vitrimers based on the Schiff base.

Vitrimers are expected to combine features of thermosets and thermoplastics but their continuous reprocessing is still a challenge; poly­(ethylene terephthalate) (PET) has been widely used in our daily life, while its cross-linking upcycle contradicts with processability. Herein, we combined polyol with a tertiary amine structure and diepoxy to transform PET to continuously reprocessable vitrimers through an industrial twin-screw extruder. The cross-linking of PET was determined by swelling and rheology experiments, and the vitrimer feature was characterized by stress relaxation and oscillatory frequency sweep experiments. Creep resistance and mechanical properties of PET vitrimers were improved greatly relative to neat PET. Meanwhile, PET vitrimers exhibited excellent reprocessability via compression, extrusion, and injection molding suitable for industrial production. According to this work, any thermoplastics containing ester bonds should be able to be upgraded to vitrimers for additional advantages such as creep resistance, dimensional stability, insolubility, etc., without sacrificing the original processability.

Long non-coding RNAs (lncRNAs) perform a diversity of functions in numerous important biological processes and are implicated in many human diseases. In this report we present lncRNAWiki (http://lncrna.big.ac.cn), a wiki-based platform that is open-content and publicly editable and aimed at community-based curation and collection of information on human lncRNAs. Current related databases are dependent primarily on curation by experts, making it laborious to annotate the exponentially accumulated information on lncRNAs, which inevitably requires collective efforts in community-based curation of lncRNAs. Unlike existing databases, lncRNAWiki features comprehensive integration of information on human lncRNAs obtained from multiple different resources and allows not only existing lncRNAs to be edited, updated and curated by different users but also the addition of newly identified lncRNAs by any user. It harnesses community collective knowledge in collecting, editing and annotating human lncRNAs and rewards community-curated efforts by providing explicit authorship based on quantified contributions. LncRNAWiki relies on the underling knowledge of scientific community for collective and collaborative curation of human lncRNAs and thus has the potential to serve as an up-to-date and comprehensive knowledgebase for human lncRNAs.

This work highlights the exploitation of an acetal motif to build dynamic covalent networks.

Recycling thermosets have become extremely important due to their ecological and economic benefits. The development of thermosets that undergo reversible polymerization provides a solution to the end-life disposal issue of thermosetting materials. However, the synthesis and recycling of the current chemically recyclable thermosets are harsh, complex, and energyintensive, and their stability is often low. Here, we designed asymmetric acetal-containing thermosets (PRCs) from general phenolic resin and 1,4-cyclohexanedimethanol divinyl ether through one-step "click" cross-linking without using catalysts and solvents and without releasing small-molecule byproducts. PRCs exhibited conspicuous stress relaxation via a dissociative mechanism, corresponding to the superior malleability and reprocess recyclability. Importantly, PRCs presented excellent creep resistance even at 100 °C. In addition, PRCs could be readily and highly efficiently recovered to original phenolic resin via hydrolysis under specific mild acidic conditions but possessed high chemical stability under neutral conditions and even weak acidic conditions or acidic conditions in the absence of organic solvents with outstanding wettability and swellability toward the samples. Thermosets with different properties could be easily achieved via regulating raw materials. This work provides a promising dynamic covalent motif and a practical method to produce readily dual-recyclable (reprocess recyclable and chemically recyclable) thermosets with superior performance and stability.

No abstract