Synthesis and Properties of Spiro-Centered Benzoxazines

A series of thermally stable spiro-centered bis(benzoxazine) monomers (BPSPI/SPBC-Bz)s was synthesized using spirobiindane/spirobischroman phenol, different amines (aniline, p-toluidine, and 2-(4-aminophenyl)ethanol) and paraformaldehyde and was characterized by FT-IR, H-1 and C-13 NMR, and elemental analysis. The effect of incorporation of two different types of spiro-center on polymerization temperature of benzoxazine and thermal stability of resulting polymers was evaluated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The curing occurred at high temperatures in both BPSPI-Bzs and SPBC-Bzs (275 degrees C), which lowered by incorporating hydroxyl group (250 degrees C) at the end. Spirobiindane based polybenzoxazines showed higher thermal stability with T-g in the range of 295-354 degrees C, initial degradation temperature at 10% weight loss at 397-405 degrees C and char yield of 37-42% at 600 degrees C compared to spirobischroman polybenzoxazines.