Design, synthesis, flame retardancy and dielectric properties of novel aromatic hyperbranched benzoxazine

Abstract Two kinds of novel aromatic hyperbranched benzoxazines (HBs), HB-Tppa1 and HB-Tppa2, were designed and prepared by using 1,1,1-tris(4-hydroxyphenyl)ethane (THPE), p-phenylenediamine (PPA), paraformaldehyde and phenol through two different synthetic routes via Mannich condensation reaction. Fourier transform infrared (FTIR) and nuclear magnetic resonance (1H and 13C NMR) spectroscopy were employed to characterize the featured structures of these (HB-Tppa)s. HB-Tppa1 exhibits greater molecular weight than HB-Tppa2, owing to a priority of forming the hyperbranched structure for preparing HB-Tppa1 without adding capped phenol in the first step. The greater reaction enthalpy (ΔH) value of HB-Tppa1 has been provided by differential scanning calorimeter (DSC), indicating that the mass fraction of benzoxazine rings in HB-Tppa1 is higher than that of HB-Tppa2. The thermal and flame retardancy properties of poly(HB-Tppa1) superior to poly(HB-Tppa2) are affected by these mentioned factors. Besides the high glass transition temperature (Tg, ≥ 320 °C), the low total heat release (THR) and heat release capacity (HRC) values of poly(HB-Tppa)s in the range of 5.4–11.7 kJ/g and 41.5–50.5 J/(g K), respectively, suggest that they are potential nonignitable materials. Moreover, the poly(HB-Tppa)s exhibit low dielectric constants (2.27 ≥ k ≥ 2.15) in the high-frequency range of 2 to 18 GHz, which may perform well in next-generation integrated circuits.