Design of Recyclable, Repairable, and Tunable Acetal Dynamic Polymer Networks for 3D-Printing Applications

This work presents the synthesis and characterization of a series of acetal-based covalent adaptable networks. The process involves the straightforward preparation of a dynamic acetal-containing dimethacrylate that, in combination with different bioderived methacrylates and a commercially available reactive diluent, allows not only fine-tuning the properties of the materials but also the use of DLP 3D printing to obtain complex shapes with good resolution. Eventually, six different materials were prepared with glass transition temperatures (Tgs) ranging from 26 to 100 °C, and their thermal, mechanical, and thermomechanical properties were evaluated. The dynamic behavior of all formulations was characterized being able to fully relax the stress in 6 min at 160 °C, with notable differences among formulations depending on the aromatic contribution and the presence of hydroxyl groups. This fast dynamicity also enabled an optimal repairing of damaged 3D-printed pieces after a simple UV and thermal treatment, obtaining very similar properties to the pristine samples. In addition, these acetal dynamic polymer networks could be chemically and mechanically recycled, presenting a promising pathway for the sustainable use of these materials and improving their circularity.