Here, we report the fabrication of a dynamic enamine-one bond based vitrimer through amino-yne click chemistry. In contrast to amine-acetoacetate condensation, the amino-yne click reaction yields a dynamic enamine-one motif that is composed of cis/trans (3:1) isomers and has a relatively lower activation energy (35 ± 3 kJ/mol vs 59 ± 6 kJ/mol), owing to the absence of a methyl substituent. The resulting vitrimer network has superior mechanical properties and faster dynamic exchange than that of a reference vitrimer derived from amine-acetoacetate condensation, and they are attributed to the fewer network defects and the less sterically hindered exchange reaction, respectively. Lastly, the efficient amino-yne click reaction is demonstrated to be compatible with the secondary-amine substrate, which has a low reactivity toward the amine-acetoacetate condensation. The efficient and side product-free amino-yne reaction offers a powerful chemical tool for vitrimer fabrication and is potentially desirable for sealing and adhesion applications.

As a class of recyclable thermoset, vitrimers are generally constructed by introducing dynamic chemistry into various synthetic or biobased building blocks. Particularly, biobased vitrimers have drawn increasing interest because of...

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Polymer networks embedded with dynamic covalent bonds have been demonstrated to be capable of network reconfiguration. This reprocessability is often related to the network dynamics or flowability, the precise control of which highly depends on the underlying chemistry. Particularly, vitrimer materials flow at a constant crosslinking density because of the associative dynamic chemistry involved. Here, we report the fabrication of enamine-one vitrimers through an amino-yne click reaction using secondary amine substrates. Compared with primary amines, the secondary amine-based amino-yne click reaction is mild and yields less gel content (70 vs 97%) in our curing system. By modulating the substituents of the secondary amine, we show that the activation energy of the exchange reaction increases (52–90 kJ/mol) with increasing steric hindrance (piperidyl ∼ methyl < ethyl < isopropyl < tert-butyl), and a similar trend was observed in the vitrimer networks. Interestingly, piperidine exhibits reactivities (including the yielded gel content and network dynamics) comparable to that of primary amines because of the less steric hindrance related to the constrained cyclic structure. This study not only enriches the scope of amine substrates for vitrimer fabrication but also offers a convenient means to tune the network dynamics through substrate choices or combination strategies (i.e., mixing primary and secondary amines or various secondary amines).

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