Influence of Anion and Cation Structures on Ionic Liquid Epoxy-Based Vitrimers

Ionic liquids with selected anions (Tf2N-, BF4-, and PF6-) and imidazolium cations bearing two terminal epoxy groups and varying aliphatic, aromatic, and dicationic spacers were synthesized. The synthesis procedures followed ion exchange mechanisms and afforded the products in high yields. Vitrimers were prepared by curing the resins with dodecenyl succinic anhydride in the presence of a base catalyst. In a comprehensive approach, the influence of the ion structure on the cure kinetics, bond exchange reactions, and thermal, mechanical, and healing performance of the dynamic polyester networks was assessed. The tensile strength could be varied over several orders of magnitude (229 kPa-23.9 MPa), while the glass-transition temperatures ranged between 1 and 59 degrees C. Especially, the anion exchange was found to be a powerful tool to tailor the properties of the dynamic networks. By using the PF6- anion, a network with improved thermal, mechanical, and self-healing properties could be obtained.