Metal Ion-Catalyzed Low-Temperature Curing of Urushiol-Based Polybenzoxazine

In this work, urushiol-based polybenzoxazine is cured by the Lewis acid (FeCl(3), AlCl(3,) and CuCl(2)) at low temperature instead of high thermal curing temperature. The effect of the Lewis acid on structures and properties of the polymers is revealed. The relating urushiol-based benzoxazine monomer (BZ) was synthesized by natural urushiol, formaldehyde, and n-octylamine. The monomer was reacted with the Lewis acid with a molar ratio of 6:1 (N(monomer): N(Metal)) at 80°C to obtain films that can be cured at room temperature. The chemical structures of benzoxazine monomers were identified by Fourier-transform infrared spectroscopy (FTIR) and (1)H nuclear magnetic resonance spectroscopy ((1)H-NMR). The interaction between the metal ion and the polymers is revealed by X-ray photoelectron spectroscopy (XPS) and attenuated total reflectance-FTIR (ATR-FTIR). The effect of the Lewis acid on the mechanical properties, wettability, and thermal stability was investigated. The results show that the benzoxazine cured by Cu(2+) has a better performance than that cured by Al(3+) and Fe(3+).