Design and Construction of Furan and Thiophene‐Based Salicyladazine Bisbenzoxazine Resins with High Thermal Stability and Tunable Surface Properties

Abstract

We synthesized two disubstituted bisbenzoxazine monomers using furan (Fa) and thiophene (Th) derivatives: bis((3‐(furan‐2‐ylmethyl)‐7‐ol‐3,4‐dihydro‐2H‐benzo[e][1,3] oxazin‐6‐yl)methylene)hydrazine (BAZ‐Fa‐BZ) and bis((3‐(thiophen‐2‐ylmethyl)‐7‐ol‐3,4‐dihydro‐2H‐benzo[e][1,3] oxazin‐6‐yl)methylene)hydrazine (BAZ‐Th‐BZ). These monomers were synthesized via Mannich condensation of salicylaldazine (BAZ‐4OH) and paraformaldehyde (CH2O) with furfurylamine (Fa‐NH2) and thiophene‐2‐methenamine (Th‐NH2), respectively. The chemical structures of BAZ‐Fa‐BZ and BAZ‐Th‐BZ were affirmed using FT‐IR and NMR; respectively. A thorough investigation of the thermal polymerization process of BAZ‐Fa‐BZ and BAZ‐Th‐BZ was conducted using DSC, TGA, and in situ FT‐IR spectra (ranging from 25 to 250 °C). Poly(BAZ‐Fa‐BZ) exhibited superior thermal properties with a thermal decomposition temperature (Td10) of 402 °C and a char yield of 58 wt.% after thermal treatment at 250 °C, along with a lower surface free energy of 28.9 mJ m−2 compared to poly(BAZ‐Th‐BZ) (Td10 = 359 °C, char yield = 48 wt.%, and surface free energy = 34.1 mJ m−2). Additionally, poly(BAZ‐Th‐BZ/BAZ‐Fa‐BZ) blend with a ratio of 1/3 after thermal curing at 250 °C demonstrated the highest Td10 of 395 °C and a char yield of 60 wt.%. Photoluminescence (PL) measurements conducted in the solid state revealed that BAZ‐Th‐BZ, BAZ‐Fa‐BZ, and their blends emit green light when excited at a wavelength of 365 nm.This article is protected by copyright. All rights reserved