Synthesis of dynamic polymers by amino-yne click reaction using multifunctional amine

Abstract

Covalent adaptable networks (CANs) have become sustainable alternatives to traditional thermosetting materials due to their powerful reprocessing and rearrangement capabilities. Therefore, developing and investigating reversible reactions that can be used in the construction of CANs is a popular research topic. Amino-yne click chemistry is known for its green characteristics—it is a catalyst-free and efficient reaction—and is widely applied in the synthesis of bio-organic molecules, but there have been few reports on CANs, especially multifunctional amine-based amino-yne click reactions. In this study, various CANs were synthesized via the amino-yne click reaction using multifunctional amines (diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA)), and they were compared with CANs that were prepared from a primary amine (tris(2-aminoethyl) amine (TREN) and a secondary amine (tris[2-(methylamino)ethyl]amine (TMEN)) under the same conditions. The results showed that H-DETA CANs exhibited the smallest glass transition temperature Tg (15 °C) and Young's modulus (105 MPa) because the crosslinker (DETA) contained a low content of primary amine and secondary amine, but its crosslinking density followed the trend of H-TMEN < H-DETA < H-TREN. In addition, the relaxation time, activation energy, and creep rate results for the CANs followed the same trend as the crosslinking density. With the increase in the secondary amine content of the multifunctional amines, the Tg of the CANs increased from 15 °C to 57 °C, the Young's modulus increased from 105 to 666 MPa, and the crosslinking density increased from 955 to 2690 mol/m3. Notably, the increase in the secondary amine content led to the weaker dynamics of the material, namely, prolonged relaxation time, increased activation energy, and decreased creep rate. This work also verified the dynamic exchange mechanism of the materials by the molecular model reaction and the amine solvent dissolution tests. Finally, hot-pressing experiments demonstrated the good plasticity and recovery ability of prepared CANs. This work provides an elegant path for preparing materials in energy and chemical fields such as coatings and rubber.