Performance-modified polyimine vitrimers: flexibility, thermal stability and easy reprocessing

Polyimine vitrimers are a promising class of self-healing materials for their attractive dynamic reversible properties and ease of preparation without catalysts, but they still remain some challenges to overcome, such as poor mechanical properties and thermal stability or a higher temperature to reprocess and recycle. Herein, performance-modified polyimine vitrimers, combining flexibility, good mechanical properties and thermal stability with easy reprocessed/recycle properties, were studied by introducing aromatic diamines dimer (m-xylylenediamine dimer) into the polymer networks. The incorporation of m-xylylenediamine dimer increases the molecular chain of polymer networks, which makes the material more flexible and easy reprocessed. Besides, it owns two benzene rings and endows the dynamic polymer with broaden conjugation structure, which remains the material’s thermal stabilities and mechanical properties. Results show that the polymer material exhibits flexibility at room temperature [a glass transition temperature (T_g) of 72 °C, a storage modulus of = 1.56 GPa and stress at break of = 45 MPa (dry sample) and 27 MPa (wet sample)], possesses excellent thermal stability (a mass loss of 6.3% at 300 °C) and performs viscoelastic liquid behavior in very short relaxation times at lower temperatures (from 260 s at 70 °C to 22 s at 100 °C). In addition, the obtained networks could be more easily reprocessed and remolded in shorter times and at lower temperatures under the condition of heat, water and amine solvents without adding any catalyst.