Synthesis and characterization of high thermal resistance acetal-containing heterocyclic polyamides

•Heterocyclic acetal-containing Monomer was prepared as a substrate for the catalyst.•DHNF were fabricated were prepared with two different diacid monomers.•Acetal functional group improved polyamide solubility and processability. Viscometry results showed higher inherent viscosity. This study synthesized a heterocyclic acetal-containing monomer, 7a,14c-dihydronaphtho[2,1-b] naphtho [1′,2′:4,5] furo[3,2-d] furan (DHNF) with a melting point of 230 °C, through the acidic reaction of 2-naphthol and glyoxal. Two types of heterocyclic polyamides were produced via condensation polymerization of DHNF Diamine with terephthalic acid (aromatic diacid) and sebacic acid (aliphatic diacid), achieving melting points exceeding 400 °C. Spectroscopic methods, including Fourier-transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance spectroscopy (1HNMR), were used to identify the synthesized compounds. Thermal analysis, including Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), demonstrated the thermal stability of the polyamides with acetal functional groups, showing a 10 % weight loss at 193.6 ℃ for PA-1 and 420 ℃ for PA-2, with crystallization temperatures of 155 °C and 180 °C for Types 1 and 2, respectively. The results indicate that the acetal functional group enhances polyamide solubility and processability. Viscometry revealed higher inherent viscosity for PA-2, attributed to its higher molecular weight.