Incorporation of Dynamic Dissociative Crosslinkers in Associative Covalent Adaptable Networks: Towards Controllable Flow in Vitrimers

Dynamic covalent bonds (DCBs) are stimuli responsive bonds that can be activated thought different sources such as light, pH and force. Researchers have incorporated these bonds into conventional polymer networks to increase the recyclability and performance of these materials. A key challenge in using DCBs is the uncontrolled flow of the material due to the presence of unreacted sites and end groups. These topological features can remain active after the polymerization and affect the dynamics of the system. Here, we show that the incorporation of monofunctional dissociative DCBs that use the same reactive intermediates as associative DCBs can be used to control both the on-set and rate of flow. Using a combination of “real-time” spectroscopic measurements, we find that reactive chain ends can be generated in situ via changes in temperature. Importantnly, while rheological methods show an increase of the storage modulus through different frequencies suggesting constant crosslinking density, material relaxation was observed once the material had significant number of ‘free’ bonding groups at high temperatures. With this approach, we will tackle (1) reactivity of DCBs and (2) control the onset and rate of associative exchange of the material by combining multiple dynamic chemistries into one crosslinked network.