Design and synthesis of pendant naphthalene-based aromatic polyesters: structure-property relationship, solubility, and thermal behavior

Aromatic polyesters were synthesized from 3,5-dihydroxy-N-(4-(naphthalen-8-yloxy)phenyl)benzamide via interfacial polycondensation with varying molar ratios of isophthaloyl chloride (IPC) and terephthaloyl chloride (TPC). The diol precursor was synthesized by Yamazaki condensation and characterized using FT-IR, 1 H NMR, and 13 C NMR spectroscopy. The resulting polyesters were obtained in high yields (84–93 %) with inherent viscosities in the range of 0.37–0.54 dL g −1 , confirming moderate chain lengths. Solubility studies revealed that all polyesters were soluble in NMP, DMF, DMAc, and DMSO, partially soluble in THF and m-cresol, and poorly soluble in chloroform and dichloromethane. Thermogravimetric analysis (TGA) indicated good thermal stability, with initial decomposition temperatures of 151–169 °C, 10 % weight-loss temperatures ( T 10 % ) of 369–425 °C, and residual weights of 34–53 % at 800 °C. Differential scanning calorimetry (DSC) showed glass transition temperatures ( T g ) ranging from 109 to 129 °C. The incorporation of bulky naphthyl pendant units and ether linkages disrupted chain packing, enhancing solubility while retaining thermal stability. These results suggest that the synthesized polyesters possess a balanced combination of solubility and thermal resistance, making them potential candidates for applications in membranes, coatings, and other processable high-performance materials.