Thermal Stable and Flexible Bio‐Based Polybenzoxazine with Epoxy‐Functionalized Poly(dimethylsiloxane) Hybrids

In this study, a monofunctionalized bio‐based benzoxazine monomer (VAnBZ‐CN) is synthesized by condensation of vanillin, formaldehyde, and aniline, and a bifunctional epoxy‐functionalized poly(dimethylsiloxane) (PDMS‐epoxy) is also prepared through hydrosilylation reactions with allyl glycidyl ether. By blending the inorganic PDMS‐epoxy with the VAnBZ‐CN benzoxazine monomer, an organic/inorganic hybrid material is formed, which exhibited enhanced thermal stability after thermal curing polymerization. The improved thermal stability observed in the hybrid material can be attributed to a combination of the formation of the triazine structure by VAnBZ‐CN and the presence of the inorganic part of PDMS‐epoxy on the surface. For example, the PDMS‐epoxy/VAnBZ‐CN = 1/1 hybrid showed the thermal decomposition temperature ( T d10 ) of 309 °C, the glass transition temperature ( T g ) of 165 °C, and the char yield of 54 wt.% after the thermal curing polymerization process conducted at 240 °C based on thermogravimetric (TGA) and dynamic mechanical analyses (DMA). Furthermore, the char yield of the hybrid material with PDMS‐epoxy/VAnBZ‐CN = 1/3 is higher than that both of pure VAnBZ‐CN and PDMS‐epoxy after the thermal curing polymerization process. This result indicates that the addition of PDMS‐epoxy resin can improve the formation of a char residue and then enhance the resistance to thermal decomposition for their overall thermal stabilities.