Facile Preparation of Polyimine Vitrimers with Enhanced Creep Resistance and Thermal and Mechanical Properties via Metal Coordination

TLDR

Vitrimers enable reprocessing of thermosets through dynamic bond exchange, yet their susceptibility to creep compromises dimensional stability and limits applications. This study aims to mitigate creep by incorporating metal complexes into a cross‑linked polyimine vitrimer. A one‑pot synthesis introduces Fe³⁺, Cu²⁺, and Mg²⁺ complexes into the polyimine network, forming metal‑coordinated vitrimer cross‑links. The resulting metal‑coordinated vitrimers exhibit reduced creep (from 30 % to 20 % at 60 °C with 0.5 % Cu²⁺), higher initial creep temperatures (≈100–120 °C), increased activation energy, and enhanced thermal, mechanical, and chemical stability while retaining recyclability.

Abstract

Vitrimers undergoing dynamic bond exchange enable reprocessing and recycle of thermosets. However, vitrimers are susceptible to creep, leading to their poor dimensional stability, which limits their applications. Here, a facile method via integration of metal complexes was utilized to address this issue, and cross-linked polyimine was selected as an example of vitrimer. Three different metal complexes were introduced into a polyimine vitrimer via a one-pot preparation involving the formation of metal complexes and cross-linking of polyimine. The addition of 0.5 mol % Cu2+ relative to imine bond reduced creep degree from 30% to 20% at 60 °C, and the creep resistance was enhanced with increasing Cu2+ content. Loading 5 mol % Cu2+ increased the initial creep temperature from 60 to about 100 °C and raised the Arrhenius activation energy (Ea) for stress relaxation from 52.3 to 67.7 kJ mol–1. The ability of different metal complexes to suppress creep followed the order of Fe3+ > Cu2+ > Mg2+, and the initial creep temperature reached around 120 °C for vitrimer with 5 mol % of Fe3+. Meanwhile, the polyimine–metal complex vitrimers still exhibited excellent reprocessing recyclability. Moreover, the introduction of coordination structures enhanced the thermal and mechanical properties, solvent, and acid resistance. Thus, metal coordination is an efficient approach to achieve high-temperature creep resistance, excellent thermal and mechanical properties, and chemical stability for vitrimers based on the Schiff base.