From the Design of Novel Tri- and Tetra-Epoxidized Ionic Liquid Monomers to the End-of-Life of Multifunctional Degradable Epoxy Thermosets

The design and development of multifunctional epoxy thermosets have recently stimulated continuous research on new degradable epoxy monomers. Herein, tri- and tetra-epoxidized imidazolium monomers were rationally designed with cleavable ester groups and synthesized on a multigram scale (up to 100 g), yielding room-temperature ionic liquids. These monomers were used as molecular building blocks and cured with three primary amine hardeners having different reactivities, leading to six different network architectures. Overall, the resulting epoxy-amine networks exhibit high thermal stability (>350 degrees C), excellent mechanical properties combined with a shape memory behavior, glass transition temperatures (T(g)s) from 55 to 120 degrees C, and complete degradability under mild conditions. In addition, nonpolarizable, all-atom molecular dynamics simulations were applied in order to investigate the molecular interactions during the polyaddition reaction-based polymerization and then to predict the thermomechanical and mechanical properties of the resulting networks. Thus, this work employs computational chemistry, organic synthesis, and material science to develop high-performance as well as environmentally friendly networks to meet the requirements of the circular economy.

Automated summary

This study focuses on the design and development of multifunctional epoxy thermosets using new degradable epoxy monomers. Through rational design and synthesis, six different network structures were formed by curing the monomers with primary amine hardeners. The resulting epoxy-amine networks exhibited high thermal stability, excellent mechanical properties, shape memory behavior, wide range of glass transition temperatures, and complete degradability. Molecular dynamics simulations were also utilized to predict the properties of the networks.