Covalent adaptable networks (CANs) are a promising class of polymer materials which uniquely bridge the gap between thermoplastics and thermosets. Through the exchange of dynamic crosslinks, CANs undergo molecular network rearrangement (MNR) that allows these crosslinked materials to be (re)processed similarly to thermoplastics. However, conventional CANs often differ considerably in their constitution and mechanical performance compared to industrial thermosets, posing challenges to their rollout. Here, using the commercial thermoset polydicyclopentadiene (pDCPD), we demonstrate that via judicious design of molecular additives, existing thermosets can be transformed into CANs at low additive loadings, with controlled relaxation kinetics. We introduce three distinct chemistries for the additive-enabled deconstruction of pDCPD thermosets, utilizing silyl ether + Brønsted acid, boronate + alcohol, and Meldrum’s Acid derivative + thiol, expanding the chemical scope of our approach. Using the silyl ether platform as a model system, it is shown that exchangeable crosslinks are not necessary to enable MNR, and instead, the incorporation of dynamic linkages within polymer backbones can be sufficient, even in the presence of 100% static crosslinks. Using as little as 10 volume % additive in combination with commercially available small-molecule catalyst, we demonstrate MNR in pDCPD with no statistically significant change in mechanical properties compared to native pDCPD. This new insight into CAN design suggests that any commercial thermoset can be effectively ‘CANonized’ with an appropriate polymerizable additive.

Dynamic comonomers enable conversion of thermosets into covalent adaptable networks

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.