Structural effects of diamines on synthesis, polymerization, and properties of benzoxazines based on o-allylphenol

Two allyl-containing bifunctional benzoxazines (oAP-hda and oAP-dds) were synthesized from o-allylphenol, formaldehyde, and two diamines [1,6-hexamethylenediamine (HDA) and 4,4'-diaminodiphenyl sulfone (DDS)]. The chemical structures of oAP-hda and oAP-dds were confirmed by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The reactivity of HDA is higher than that of DDS in the synthetic reaction of benzoxazines, and the polymerization temperature of oAP-hda is lower than that of oAP-dds. The structure changes from benzoxazines to their corresponding polybenzoxazines [Poly(oAP-hda) and Poly(oAP-dds)] were studied by FTIR and solid state 13C NMR. The dynamic mechanical properties and thermal stabilities of Poly(oAP-hda) and Poly(oAP-dds) were studied by dynamic mechanical analysis and thermogravimetry, respectively. The storage moduli in the glassy state are 1.44 and 3.18 GPa for Poly(oAP-hda) and Poly(oAP-dds), respectively, and the glass transition temperatures are 87 and 193 degree C, respectively. The thermal stability of Poly(oAP-dds) is much higher than that of Poly(oAP-hda).