Falin Li,Yi Wang,Qiu Wang,Binbo Wang,Shuai Du,Fengyuan Zhang,Songqi Ma
This work discloses a new strategy based on dynamic cross-linking chemistry to achieve advanced one-component thermosets combining ultralong storage life and fast cross-linking. One-component thermosets containing resin and cross-linker in one pot have the features of simple operation, stable quality, and low waste; however, an urgently needed one with long storage life at room temperature and fast cross-linking at medium–low temperatures (≤130 °C) remains an enormous challenge. Herein, we innovatively propose a strategy of dynamic cross-linking and controlled dissolution to address this issue. As an example, a dynamic cross-linked cross-linker (DCC) is synthesized via Diels–Alder reaction to hide the high activity of a commercial amine-type cross-linker. A one-component thermoset from a DCC and a commercial diepoxy monomer can be stored for an ultralong time at room temperature and cross-linked rapidly below 130 °C. Moreover, the DCC can also serve as a latent accelerator for epoxy/anhydride thermosets with the same storage life as the control system with no accelerator at room temperature and fast cross-linking at elevated temperatures. This work is beneficial for promoting the application of dynamic cross-linking chemistry and meeting the urgent need for advanced one-component thermosets in the fields of advanced composites, coatings, electronic packaging materials, automotive and electronic adhesives, etc.
It is very crucial to develop ideal tissue adhesive materials with high toughness, super tissue adhesion, biodegradability and biocompatibility for the treatment of accidental trauma and surgery. Inspired by mussels, a novel injectable bioadhesive chitosan-based hydrogel was developed by dual-ionic crosslinking in this paper, which was composed of catechol-modified chitosan (Cat-CS), thermosensitive polymer (PNAM) and NaHCO 3 . The gelation time of Cat–CS–PNAM/NaHCO 3 hydrogel is 50 s at 37 °C, showing good sol-gel transition under different temperatures. The prepared hydrogels have the ability to adhere to a variety of materials surface, wherein the adhesion strength to metal surface is 126.20 ± 15.17 kPa. They also possess compact microstructure and excellent dry/wet adhesion to tissues due to the interaction between catechol/amino groups and tissues, combined with physical crosslinking . In addition, the hydrogels can be completely degraded after 14 days in vitro and show good cytocompatibility. This newly designed mussel-inspired chitosan hydrogels have the characteristics of injectability , fast gelation, bioadhesion and biocompatibility, with great potential for application in biomedical fields .
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