Vitrimers represent an interesting class of materials that exhibit many of the desirable properties of conventionally crosslinked materials, while also being able to be reprocessed through the utilization of dynamic exchangeable crosslinks. Recently, the thiourethane moiety has been explored as a potential dynamic crosslink in vitrimeric materials, as it exhibits both associative and dissociative exchange pathways in response to an external stimulus. Herein, we aim to utilize the selectivity of various thiol-X reactions to achieve rapidly forming vitrimeric systems. In the present study, a sequential “one pot – two step” process was utilized to develop a series of ternary thiol-ene/thiourethane networks with varying crosslink densities to understand how these systematic changes in network architecture effect the material’s vitrimeric behavior. Each network studied exhibited rapid curing under UV irradiation, consistent with photocured thiol-ene network fabrication, and excellent network reprocessibility imparted by the dynamic exchange of the thiourethane linkages. By relating the relative rates of stress relaxation to the Arrhenius relationship, we were able to determine that crosslink density plays a crucial role in the E<sub>a</sub> and T<sub>v</sub> of this class of materials. Furthermore, we found that the crosslink density is pivotal in maintaining the mechanical properties of these materials as a function of reprocessing.

Network architecture effects on the vitrimeric behavior of ternary thiol-ene/thiourethane covalent adaptable networks

ACS Spring 2022

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