Thermally Assisted Self-Healing and Shape Memory Behavior of Diphenolic Acid-Based Benzoxazines

Two diphenolic acid-based benzoxazines are designed and crosslinked to form smart polymers with shape memory and self-healing ability. Aliphatic molecules of stearylamine and jeffamine are selected with the intent to introduce network flexibility and mobility in the designed copolymer system. While stearylamine is incorporated to form a more rigid benzoxazine molecule (DaSa), aliphatic polyether molecule of jeffamine in benzoxazine (DaJa) allows system mobility. Prepared benzoxazine precursors are characterized by nuclear magnetic resonance and IR method, while thermomechanical properties are determined by differential scanning calorimetry and dynamic mechanical analysis. Glass transition temperature increases with the increasing proportion of the more rigid benzoxazine from stearylamine ranging from 6 to 104 degrees C. All prepared copolymers show promising self-healing and shape memory abilities proved by fracture toughness and self-deploy tests, respectively. The best results are reached at 50 and 60 wt% of DaSa benzoxazine (glass transition temperature being 83 and 84 degrees C) in the copolymer system with self-healing ability of 50-60% in three consecutive cycles, shape fixity above 90%, and shape recovery over 90%. The synthesis chemicals such as diphenolic acid, jeffamine, stearylamine, and paraformaldehyde can be of a natural origin having a great potential to develop a bio-based system.