Fixing Pillar[5]Arene-Based Rotaxanes Into Epoxy Networks to Produce Toughened Epoxy Resins

Introducing mechanical interlocking into epoxy thermosets can enhance material performance. However, this method typically requires complex monomer design and elaborate synthesis. Here, we demonstrate a simple strategy that exploits the dual functionality of a commercially available hydroxylated pillar[5]arene, which acts simultaneously as a macrocyclic host and a rigid cross-linking unit. By threading polymer chains through the macrocycles, poly(pseudo)rotaxanes consisting of rigid wheels and flexible axles were formed. Then, in situ curing fixed the pillar[5]arene into the epoxy networks through both mechanical and covalent bonding. The resulting materials exhibited a balanced combination with tensile strength of 29.7 MPa and toughness of 21.6 MJ·m^-3. This approach enabled fine-tuning of the mechanical properties of the epoxy networks by varying the pillar[5]arene content and epoxy precursor lengths. By combining supramolecular threading with covalent network formation using a single macrocycle, this work provides a convenient and practical route to regulating epoxy network properties.