Ionic liquid-reinforced polybenzoxazine/urethane film with robust surface for recoverable adhesive tape substrate

Surface with low energy plays an irreplaceable role in antifouling coatings, national defense and military industry. However, low-energy surface has poor surface stability, which leads to the difficulty of recovery and massive waste. Thus, it is urgent to exploit low surface free energy materials with excellent surface stability. In this work, a series of ionic liquid-reinforced polybenzoxazine/urethane (poly(DHB/PU)) films was prepared, the dihydroxybenzoxazine (DHB), stearyldiethanolamine (SDEA) and hydroxyl-terminated polydimethylsiloxane (HTPDMS) introduced into the molecular chains provide the films low-surface-energy properties. Then, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid (IL) were added into the poly(DHB/PU) system. The comprehensive properties of the modified films were further improved, including recoverability, outstanding thermal stability (10 % weight loss temperature ranged from 270.51 to 308.51 °C), solvent resistance and low surface free energy (average 20 mN/m). Besides, the dense hydrogen bonds formed between imidazolium groups in IL and carbamates are the critical factor for optimizations of compatibility and mechanical properties. The higher the content of IL, the better the compatibility, the better the mechanical properties (elastic modulus varied from 63.32 MPa to 124.57 MPa) and the lower the peel strength (<7.975 gf/in) of the films. The synthesized polymer has great potential in the application of recoverable adhesive tape substrate.