Modular design of Diels-Alder reversible networks for the facile production of highly tunable materials

Abstract

Covalent adaptable networks (CANs) have attracted significant attention due to their potential to form crosslinked, yet reprocessable networks. Their ability to rearrange upon exposure to specific stimuli, in combination with properties such as self-healing can advance the development of novel materials, including for additive manufacturing. Thorough understanding of structure-property relations and processing potential will aid future application-driven research in network design as well as material selection. Therefore, a multitude of CANs were synthesized herein, by crosslinking epoxide-based oligomers via the furan-maleimide Diels-Alder reaction, to evaluate small systematic variations of (co)monomer composition, crosslinker length/flexibility and crosslinking density as vectors of tuning the CANs' thermomechanical properties. Networks with glass transition temperatures (T_g) spanning from <−40 °C up to >20 °C and Young's Moduli spanning from 0.2 MPa to >500 MPa were readily attainable. Crosslinker length/flexibility had a profound impact on the tensile properties, while changes in backbone composition provided insight into the impact of secondary interactions versus rigid moieties on mechanical performance. Self-healing at ambient conditions was demonstrated for elastomeric networks, with healing efficiency being enhanced when using longer crosslinkers. Finally, a cell viability and metabolic activity assay provided a preliminary in vitro demonstration of the biocompatibility of these materials.