Elastomeric polyolefin vitrimer: Dynamic imine bond cross-linked ethylene/propylene copolymer

In this study, a new strategy for the preparation of elastomeric vitrimer based on ethylene/propylene copolymer rubber (EPR) was proposed. Specifically, by introducing aldehyde pendants into EPR chains and then adding tris-(2-aminoethyl) amine (TREA) as cross-linking agent, an associative reversible cross-linking network based on dynamic imine bond was constructed in EPR. Since the imine exchange reaction can be controlled by adjusting the temperature without catalyst, the EPR reversible cross-linking was realized efficiently in solid polymers. Moreover, the cross-linking density as well as the material mechanical properties could be tuned by simply varying the aldehyde group content or the aldehyde/TREA ratio. The association nature of the dynamic imine bond enabled the cross-linked EPR to maintain the network structure in xylene at 120 °C; while the imine bond exchange reaction rate accelerated as the temperature increased. The activation energy of the cross-linking reaction was calculated to be 57.2 kJ mol−1 according to the dependence of the imine bond exchange reaction rate on temperature, which also endowed the cross-linked network with satisfactory plasticity and recyclability.