3D-Printable Shape-Memory Polymers Based on Halogen Bond Interactions
in: Advanced Functional Materials (2022)
The supramolecular halogen bonding (XB) is utilized for the first time for the preparation of shape-memory polymers. For this purpose, an iodotriazolebased bidentate XB donor featuring a methacrylamide is synthesized. Free radical polymerization of the XB donor monomer together with butyl methacrylate, triethylene glycole dimethacrylate, and methacrylic acid results in covalently cross-linked polymer networks bearing both, halogen bond acceptors and donors, in their side chains. While the reversible halogen bond interactions can act as switching unit, the required stable phase of the shape-memory polymers is formed by covalent cross-links. The successful formation of the supramolecular cross-links is proven via Fourier-transform Raman spectroscopy. Furthermore, the thermal properties are investigated via differential scanning calorimetry and thermo gravimetric analysis. Thermo-mechanical analysis reveals excellent shape-memory abilities with fixity rates above 95% and recovery rates up to 99%. Moreover, it is possible to 3D-print this kind of material exhibiting the ability to recover its shape within a few seconds at 130 °C.