Synthesis and characterization of heterocyclic core-based polybenzoxazine matrices

In the present work, four types of heterocyclic core-based polybenzoxazine matrices (HC-PBZ) developed based on pyridine, thiophene, and thiazole and their molecular structure, thermal, flame-retardant and luminescent properties were studied and discussed. The heterocyclic core-based benzoxazine monomers (HC-BZ) were synthesized using two types of phenols (phenol, and 4-hydroxyphenylacetonitrile), and two types of heterocyclic diamines [2,6-Bis-(4-aminophenyl)-4-thiophen-2-yl-pyridine (BATP) and 4-(2-methylthiazol-5-yl)-2,6-bis-(4-aminophenyl)-pyridine (BAMTP)] with formaldehyde through Mannich reaction. The structure of the four HC-BZ monomers was confirmed by various spectral analysis such as Fourier-transform infrared spectroscopy (FTIR), and Nuclear magnetic resonance spectroscopy (¹HNMR and ¹³CNMR). All the four HC-BZ monomers have the maximum range of curing temperature (T_p) between 252 and 267 °C. Data resulted from the thermal studies indicate that the HC-PBZ exhibits better T_g, thermal stability and flame-retardant properties. Among the four HC-PBZ systems the thiazole based system possesses the higher value of T_g of 268 °C and thermal stability when compared to those of other matrices. It was also observed that the HC-BZ monomers and HC-PBZ polymers exhibit a photoluminescent (PL) emission range between 441–445 and 414–417 nm, respectively. Overall, it seems that the thiazole and thiophene based HC-PBZ can be considered as competitive materials for luminescent applications with high thermal and flame-retardant properties.