Design of interpenetration network in light-based 3D printing for robust and sustainable dielectric insulators

The sustainability and additive manufacturing of dielectric insulators are the development direction of the power system. Introducing dynamic covalent bonds in light-based 3D printing have attracted considerable attention as the reversible crosslinks allow for the reprocessing of printed objects. However, there generally exists a trade-off between mechanical strength, glass transition temperature (T_g), and reconfigurability for dynamic covalent networks. The reconfiguring process of the dynamic covalent network often requires high mobility of molecular chains and large free volumes, which in turn decreases the mechanical strength, T_g, and electrical insulating performance. Herein, we demonstrate a novel strategy for developing a kind of mechanically robust and sustainable vitrimer by building a rigid-flexible coupling inter-penetration network (IPN). Specifically, a two-stage curing approach was used to prepare high-performance 3D-printing vitrimers by using the plant oil-epoxy hybrid resin, which brings a lot of ester bonds and β-hydroxyl ester for the crosslinking network. Computational techniques with molecular dynamics calculation are used for the design and optimization of the crosslinking network, and then the optimized IPN is prepared by digital light processing 3D printing and subsequent heat curing. In the IPN, the epoxy backbone is rigid to enhance the T_g and tensile strength, while the plant-based methacrylate is flexible to guarantee topological rearrangement at elevated temperatures. Compared to reported epoxy vitrimers, the resultant IPN exhibits simultaneous high T_g (111 °C), outstanding tensile strength and toughness (tensile strength of 70 MPa, elongation at break of 17.58 %), good topological rearrangement, and excellent dielectric properties (permittivity less than 4, breakdown strength of 49.3 kV/mm). This work provides a new strategy for balancing the strength, toughness, electrical insulating and sustainability of 3D-printed thermosets.