Consequences of Monomer Impurities on Network Characteristics and Dynamic Mechanical Behavior of an Eugenol-based Covalent Adaptable Network

Covalent adaptable networks (CANs) are an emerging class of polymers exhibiting the potential to introduce recyclability into polymer networks. For industrial applications, robustness of material properties and predictable dynamic behavior are highly desirable. In this study, diepoxides of varying purity were used to prepare hybrid CANs. Hybrid CANs are based on both dynamic vinylogous urethane bonds and permanent bonds formed by the reaction of amines and epoxides. We specifically investigate the robustness of the materials dynamic exchange behavior against impurities that impair or modify the network characteristics. Stress relaxation experiments reveal that the dynamic behavior remains relatively stable up to ca. 23 % monomer impurity. At higher impurity levels we observe pronounced changes of the exchange dynamics. All materials, regardless of purity, exhibit incomplete stress relaxation. Macroscopic manifestations of this fact are visible defects in the nominally purest materials upon reshaping. Thermal and dynamic-mechanical analyses further show that network density and glass transition temperature decrease with increasing impurity, while overall the thermal stability remains largely unaffected. The results demonstrate that hybrid CANs based on vinylogous urethane exchange chemistry can tolerate moderate monomer impurities without losing key dynamic properties, offering insights for industrial-scale processing and material design.