Design of a Recyclable Thiol–ene Network with Dynamic Ether Linkages: Regulations of Creep and Dynamicity

Thiol–ene click chemistry has been widely used for synthesizing cross-linked polymers, but conventional networks contain irreversible thioether bonds, preventing reprocessing and contributing to waste. To address this, dynamic covalent linkages have been introduced. However, designing chemistry that permits the dynamicity and robustness of the network is a formidable challenge. Besides, regulating dynamicity and creep in the network bearing the dynamic linkages remains another major challenge. To address these challenges, this report presents a strategy to design a robust and dynamic ether-based cross-linked polymer prepared using click chemistry, wherein the creep and dynamicity were regulated by systematically varying the cross-link density in the network. The polymers were prepared using the polymerization of a benzylic ether-based trifunctional alkene with dithiols of varying chain length. The ether linkage enables robustness to the resultant polymer. The employed thiol–ene click chemistry permits a broader scope of the monomers and thus enables tuning of the properties of the resultant polymer. The usages of dithiols with increasing chain length by four methylene units, namely, 1,2-ethanedithiol, 1,6-hexanedithiol, and 1,10-decanedithiol, permitted us to regulate the thermal and mechanical properties of the polymers. The polymers exhibited a noteworthy thermal robustness and chemical stability. Additionally, the shape memory behavior of the polymers was demonstrated. The creep in the polymers was found to be strongly influenced by the cross-link density; with the increase in cross-link density, the creep increased. The dynamic ether linkages impart malleability and reprocessability, enabling the efficient stress relaxation of polymers. The dynamicity of the network was regulated by the dithiol chain length. Finally, to address the end-of-life challenge, degradation and chemical recycling of polymers were demonstrated. Furthermore, an upcycling strategy was demonstrated by repurposing the degraded monomer to construct a new dynamic network with improved mechanical properties. This work will broaden the scope of thiol–ene chemistry and open new avenues for the development of robust and recyclable cross-linked polymers with tunable material and dynamic properties.