A phosphinated tetracyanate ester (4) was prepared by a three-step procedure, including nucleophilic addition of DOPO on 5,5′-methylenebis(2-hydroxybenzaldehyde), electrophilic substitution of phenol, and nucleophilic substitution with cyanobromide. Tetracyanate ester (4) was applied to copolymerize with a 4,4′-oxydianiline/phenol-based benzoxazine (P-oda) to enhance the properties of P-oda thermoset. We discussed the miscibility, microstructure, as well as the thermal and dielectric properties of the reactive blends of (4) with a P-oda. A miscible blend can be achieved in all compositions, as judged by thermal analysis. The co-reactions between (4) and P-oda, as observed in the IR analysis, explain the single-Tg phenomenon. The experimental data show that the thermal, dielectric and flame retardant properties of polybenzoxazine are enhanced through the reactive blends.
