Hybrid polybenzoxazine with tunable properties

The difunctional urushiol-based benzoxazine (U-da) was synthesized by utilizing urushiol, 4,4′-diaminodiphenyl methane (DDM) and formaldehyde. The 3,3′-phenylmethanebis(3,4-dihydro-2H-1,3-benzoxazine) (P-da) was prepared by the similar procedure with DDM, phenol and formaldehyde. The U-da and P-da were cured into hybrid polybenzoxazine with different U-da fractions, where the alkyl chains in urushiol can improve the ductility of the polybenzoxazines. Fourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) studies demonstrate that the thermally activated ring-opening polymerization can happen at a relatively low temperature (∼180 °C) without addition of catalyst. The hybrid polybenzoxazines were measured by thermal gravimetric analysis (TGA). It shows the temperatures corresponding to the 5% and 10% weight loss are slightly affected by the U-da content whereas the residual weight at 800 °C increases with P-da content. Dynamic mechanical analysis (DMA) studies indicate that the hybrid polybenzoxazine with U-da content of 50 wt% has a relatively high elongation (10%) and stress (101 MPa) at break. The properties of the hybrid polybenzoxazine can be tuned by the composition.