A Simple Design of UV-curable Covalent Adaptive Networks Operated by Thiourea Bond Exchange

Using the concept of covalent adaptive networks (CANs), or vitrimers, sustainable and reprocessable cross-linked polymer materials can be developed. Advances in molecular design and understanding of the underlying physics are essential for translating such bond exchange concepts into practical applications. In this study, we demonstrate the design of a simple CAN system via UV-curing of a thiol-ene click reaction, where the network is formed by reacting telechelic allyl monomers with tri-functional thiol cross-linkers. The telechelic allyl monomer, containing thiourea bonds, is synthesized specifically for this purpose, with thiourea units acting as dynamic bond exchange sites within the network. Notably, this design offers broad tunability in the topological and chemical features, highlighting an important principle in the development of model CANs for physical property investigation. Here, we evaluate curing behavior, temperature-sweep rheological properties, stress relaxation, and recyclability for a representative formulation, providing insights into simple yet versatile design strategies.