Sequential Thiol Click Reactions: Formation of Ternary Thiourethane/Thiol-Ene Networks with Enhanced Thermal and Mechanical Properties

We report the physical properties of thiol-ene networks modified with thiourethane or urethane linkages, either along the main chain or as a branched component in the network, respectively. Because of the robust and orthogonal nature of thiol-isocyanate and thiol-ene reactions, these networks can be formed in a two-step, one-pot synthesis. Resultant networks were characterized using dynamic mechanical analysis, mechanical testing and other complementary techniques. It was found that incorporating (thio)-urethanes into the networks increased T-g, but also increased strain at break and toughness while decreasing cross-link density. The changes in physical properties are discussed in terms of a proposed dual network morphology. These facile modifications to thiol-ene networks demonstrate how molecular-level, nanoscale changes can have a profound influence on the macroscale properties through hierarchical development of network morphology.