Experimental Protocols for Addressing the Viscoelasticity of Vinylogous Urethane Vitrimers

Covalent adaptable networks (CANs) are a new class of polymer materials that present the mechanical performance of thermosets and the recyclability of thermoplastics. This unique combination is based on the incorporation of dynamic covalent bonds within the polymer backbone, which permit the topological rearrangement of the network. Dynamic bonds are responsible to produce exchange reactions, either dissociative or associative, that resulted in changes in the molecular interconnectivity of the network. However, the effect of the incorporation of dynamic bonds in the viscoelastic properties of the network is under discussion, either theoretically and experimentally. In this work, we present the experimental protocol used for the determination of the viscoelastic spectra of thermally activated CANs, usually known as vitrimers. To do so, we take advantage of recently synthesized vinylogous urethane based methacrylic vitrimers and compared with similar non-dynamic networks. The protocol include time-temperature superposition (TTS) applied to small amplitude oscillatory shear (SAOS) and stress-relaxation experiments. The appearance of additional relaxation phenomena will be discussed and related to the incorporation of vinylogous urethane moieties. Finally, viscoelastic features will be correlated with the (additive) manufacturing and reprocessing/recycling capabilities of these materials.