Creep and recovery of vitrimers under thermo-chemo-mechanical coupling effects

Reprocessable, repairable, and recyclable (“3R”) vitrimers have experienced rapid development over the past decade and demonstrate significant potential for diverse applications. The creep performance of vitrimers is crucial for their dimensional stability under load-bearing conditions at relatively low temperatures and serves as a key metric for evaluating their reprocessability at high temperatures. However, the impact of dynamic covalent polymer networks (DCPNs) on vitrimer mechanics, particularly creep properties, remains debated. Systematic experimental studies on the creep of vitrimers across a wide temperature range are lacking. We use the classic epoxy vitrimer as a model system to investigate the impact of DCPNs on vitrimer mechanics, especially focusing on the creep and recovery behavior across a wide temperature range, spanning from room temperature to the glass transition temperature (T_g) and further to the topology freezing transition temperature (T_v). We systematically examined the effects of temperature, stress, and catalysts on vitrimer creep, revealing the influence of DCPNs. Our findings demonstrate significant thermo-chemo-mechanical coupling effects in the creep mechanics of vitrimers, a facet not comprehensively acknowledged in existing studies. In addition, at temperatures below T_g, vitrimers exhibit superior creep resistance compared to pure epoxy resin due to metal coordination, ensuring excellent dimensional stability under load-bearing conditions. Conversely, at high temperatures, active bond exchange reactions in vitrimers accelerate creep and result in greater residual deformation, highlighting exceptional reprocessability. This study provides new insights into the materials and mechanics of vitrimers.