Post-Modification of Polybutadienes by Photoinduced Hydrogen Abstraction from Benzoxazines and Their Thermally Activated Curing

Side-chain benzoxazine functional polybutadienes was synthesized by photoinduced hydrogen abstraction process. First, photoactive benzoxazines having both chromophoric carbonyl and hydrogen donating sites were synthesized using vanillin or 4-hydroxybenzophenone by conventional benzoxazine synthesis methodology. Irradiation of neat polybutadiene (PB) in the presence of the corresponding benzoxazines, namely benzophenone benzoxazine (BPh-ptol) and vanillin benzoxazine (Van-a) under 300-350 nm light, gave PBs with approximately 4-5 benzoxazine units per chain. Successful modification was confirmed by the spectral and thermal investigations. It is demonstrated that PBs attached with benzoxazines undergo thermally activated curing without any catalyst to form polybutadiene thermoset with high char yield.