Poly(itaconic Acid) Hydrogels with Dynamic Covalent and Supramolecular Cross-Links for High and Tunable Mechanical Properties

Aiming toward sustainability, poly(itaconic acid) has been considered as an alternative to the widely used fossil-based poly(acrylic acid). Its application has been, however, limited by its lower mechanical properties due to challenges in the polymerization processes. Herein, we report photopolymerizable and thermoreversible hydrogels based on poly(itaconic acid) allowing tunability from high strength (∼1000 kPa) plastically yielding materials to soft elastomeric-like stretchability, also allowing thermoresponsive flow, and a relatively high water absorption of 384 g/g. The thermal gel melting stems from the dynamic covalent bonds, in combination with metal-ion-mediated supramolecular connections. The materials facilitate on-demand water stability while allowing gel-to-sol melting for thermal extrusion for 3D-printing, a combination not observed in classic permanent covalent networks. To promote sustainability, biosourceable starting materials are used without additional solvents or purification steps. Given the biocompatibility of the components, potential applications can be foreseen, such as tissue growth scaffolds, medical and hygienic superabsorbents, and tough hydrogels for soft robotics.