The polymerization behavior and thermal properties of benzoxazine based on o-allylphenol and 4,4′-diaminodiphenyl methane

Three bifunctional benzoxazines ( o AP-ddm, o C-ddm, and P-ddm) were synthesized from 4,4′-diaminodiphenyl methane, formaldehyde, and three phenols , namely o -allylphenol, o -cresol, and phenol. The polymerization temperatures and activation energies of o AP-ddm and o C-ddm are very similar and higher than those of P-ddm; however, their reaction enthalpies exhibit inverse behavior. The storage moduli of the corresponding polybenzoxazines, P o AP-ddm, P o C-ddm, and PP-ddm, are approximately 2.1, 3.2, and 2.9   GPa at 25   °C, respectively, and their glass transition temperatures are 139, 166, and 198   °C, respectively. The thermal stabilities of P o AP-ddm and P o C-ddm are similar and lower than that of PP-ddm. The results indicate that polybenzoxazines based on ortho -substituted phenols provide higher flexibility than their counterparts prepared from unsubstituted phenol.