Combining Elemental Sulfur with Polybenzoxazines via Inverse Vulcanization

A novel strategy to obtain sulfur-rich polybenzoxazine copolymers by reacting allyl functional benzoxazine (BA-ala) and elemental sulfur was described. Simultaneous inverse vulcanization and ring-opening reactions of benzoxazine generated soluble copolymers in specific feed ratios. Parameters such as monomer structure and feed ratios on the polymerization were studied. The thermal stability of the copolymers was investigated and compared to that of polybenzoxazines derived from neat BA-ala by using thermogravimetric analysis and differential scanning calorimetry. The surface properties of the materials as examined by scanning electron microscopy confirmed that elemental sulfur and benzoxazine copolymers can be produced without a phase separation at the micrometer level. Moreover, a sponge-like insoluble macroporous polybenzoxazine networks was obtained at the 20 wt % feed ratio of sulfur.