The imidazole functionality, notably present in histidine, has been used to impart stimuli-responsiveness to polymeric materials, e.g. enabling self-healing through metal coordination bonds, drawing inspiration from byssal mussel threads. Self-healing increases lifetime, efficiency, and environmental safety of materials. Most reports on imidazole-containing polymers discuss the microencapsulation of imidazoles or their use as side chains. Here, we aim to research networks with only coordination crosslinking points to better understand the physical properties. Due to its high functional group tolerance, we used thiol-ene chemistry to incorporate imidazoles into addressable networks. Linear dithiols were modified with vinyl imidazole to yield mono and disubstituted monomers. The monomers were then reacted with various metal salts to form crosslinked networks. In the case of the mono substituted thiol-enes, a secondary linear ene was introduced to form the complete network. Differential scanning calorimetry and rheologic measurements were taken to understand the effect of different metals on the network properties. Positron annihilation lifetime spectroscopy was used to probe the free hole volume changes due to the different crosslinks, while dynamic mechanical analysis probed the self-healing properties of the various networks. This research opens up perspectives for polymeric membranes increased use lifetime, thereby decreasing polymeric waste.

Understanding the incorporation of transition metals into imidazole modified thiol-ene networks for improved self-healing and other functional advancements

ACS Spring Meeting 2021

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