Catalyst‐Free Dynamic Covalent Knoevenagel/Hydrazide Condensation for Polyacylhydrazones and Covalent Adaptable Networks
Abstract
Abstract The rapid advancement of dynamic covalent chemistry (DCvC) has significantly impacted both chemistry and materials science. There is an increasing need for exploring catalyst‐free dynamic covalent reactions with large equilibrium constant ( K eq ) ranges to provide new avenues for the tailored design of dynamic polymers. Here, we report a catalyst‐free dynamic covalent condensation reaction between Knoevenagel derivatives (Kn) and hydrazides to generate acylhydrazones. Systematic small‐molecule studies validate a significant substituent effect on the Kn reactant, resulting in a wide K eq range covering nearly four orders of magnitude (0.1–719). The high K eq values (>500) achieved in polar aprotic solvents enable the catalyst‐free synthesis of high‐molar‐mass (−180 kDa) polyacylhydrazones. The retention of by‐products during polycondensation leads to concentration‐dependent topology switching between polymeric and macrocyclic acylhydrazones. By leveraging this reaction, we developed a novel covalent adaptable network (CAN) that exhibits remarkable stress relaxation properties (38 s at 160 °C), facilitating efficient thermal reprocessing while maintaining high mechanical performance. This condensation reaction enriches the dynamic covalent toolbox and offers a versatile approach for the design and fabrication of dynamic polymers with tailored mechanical and dynamic behavior.
Article Details
Authors (10)
Pengyun Li
Key Laboratory for Advanced Materials and Joint International Research Laboratory of Precision Chemistry and Molecular Engineering, Feringa Nobel Prize Scientist Joint Research Center, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Institute of Fine Chemicals, School of Chemistry and Molecular Engineering
Jingwen Zhang
Zhiqiang Wang
Chong Li
Huiping Wu
Key Laboratory for Advanced Materials and Joint International Research Laboratory of Precision Chemistry and Molecular Engineering, Feringa Nobel Prize Scientist Joint Research Center, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Institute of Fine Chemicals, School of Chemistry and Molecular Engineering
Mengying Lei
Key Laboratory for Advanced Materials and Joint International Research Laboratory of Precision Chemistry and Molecular Engineering, Feringa Nobel Prize Scientist Joint Research Center, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Institute of Fine Chemicals, School of Chemistry and Molecular Engineering East China University of Science and Technology 130 Meilong Road Shanghai 200237 P.R. China
Ge Yan
He Tian
Center of Electron Microscopy, School of Materials Science and Engineering, Zhejiang University, Hangzhou, China.
Ruirui Gu
Key Laboratory for Advanced Materials and Joint International Research Laboratory of Precision Chemistry and Molecular Engineering, Feringa Nobel Prize Scientist Joint Research Center, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Institute of Fine Chemicals, School of Chemistry and Molecular Engineering
Da‐Hui Qu
Key Laboratory for Advanced Materials and Joint International Research Laboratory of Precision Chemistry and Molecular Engineering, Feringa Nobel Prize Scientist Joint Research Center, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Institute of Fine Chemicals, School of Chemistry and Molecular Engineering East China University of Science and Technology Shanghai China